text:
/* ----------------------------------------------------------------------
 *
 *                    *** Smooth Mach Dynamics ***
 *
 * This file is part of the USER-SMD package for LAMMPS.
 * Copyright (2014) Georg C. Ganzenmueller, georg.ganzenmueller@emi.fhg.de
 * Fraunhofer Ernst-Mach Institute for High-Speed Dynamics, EMI,
 * Eckerstrasse 4, D-79104 Freiburg i.Br, Germany.
 *
 * ----------------------------------------------------------------------- */

/* ----------------------------------------------------------------------
 LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
 http://lammps.sandia.gov, Sandia National Laboratories
 Steve Plimpton, sjplimp@sandia.gov

 Copyright (2003) Sandia Corporation.  Under the terms of Contract
 DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
 certain rights in this software.  This software is distributed under
 the GNU General Public License.

 See the README file in the top-level LAMMPS directory.
 ------------------------------------------------------------------------- */

#include <cmath>
#include <cfloat>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <iostream>
#include <map>
#include <Eigen/Eigen>
#include "pair_smd_tlsph.h"
#include "fix_smd_tlsph_reference_configuration.h"
#include "atom.h"
#include "domain.h"
#include "group.h"
#include "force.h"
#include "update.h"
#include "modify.h"
#include "fix.h"
#include "comm.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "neigh_request.h"
#include "memory.h"
#include "error.h"
#include "math_special.h"
#include "update.h"
#include "smd_material_models.h"
#include "smd_kernels.h"
#include "smd_math.h"

using namespace SMD_Kernels;
using namespace Eigen;
using namespace std;
using namespace LAMMPS_NS;
using namespace SMD_Math;

#define JAUMANN false
#define DETF_MIN 0.2 // maximum compression deformation allow
#define DETF_MAX 2.0 // maximum tension deformation allowed
#define TLSPH_DEBUG 0
#define PLASTIC_STRAIN_AVERAGE_WINDOW 100.0

/* ---------------------------------------------------------------------- */

PairTlsph::PairTlsph(LAMMPS *lmp) :
                Pair(lmp) {

        onerad_dynamic = onerad_frozen = maxrad_dynamic = maxrad_frozen = NULL;

        failureModel = NULL;
        strengthModel = eos = NULL;

        nmax = 0; // make sure no atom on this proc such that initial memory allocation is correct
        Fdot = Fincr = K = PK1 = NULL;
        R = FincrInv = W = D = NULL;
        detF = NULL;
        smoothVelDifference = NULL;
        numNeighsRefConfig = NULL;
        CauchyStress = NULL;
        hourglass_error = NULL;
        Lookup = NULL;
        particle_dt = NULL;

        updateFlag = 0;
        first = true;
        dtCFL = 0.0; // initialize dtCFL so it is set to safe value if extracted on zero-th timestep

        comm_forward = 22; // this pair style communicates 20 doubles to ghost atoms : PK1 tensor + F tensor + shepardWeight
        fix_tlsph_reference_configuration = NULL;

        cut_comm = MAX(neighbor->cutneighmax, comm->cutghostuser); // cutoff radius within which ghost atoms are communicated.
}

/* ---------------------------------------------------------------------- */

PairTlsph::~PairTlsph() {
        //printf("in PairTlsph::~PairTlsph()\n");

        if (allocated) {
                memory->destroy(setflag);
                memory->destroy(cutsq);
                memory->destroy(strengthModel);
                memory->destroy(eos);
                memory->destroy(Lookup);

                delete[] onerad_dynamic;
                delete[] onerad_frozen;
                delete[] maxrad_dynamic;
                delete[] maxrad_frozen;

                delete[] Fdot;
                delete[] Fincr;
                delete[] K;
                delete[] detF;
                delete[] PK1;
                delete[] smoothVelDifference;
                delete[] R;
                delete[] FincrInv;
                delete[] W;
                delete[] D;
                delete[] numNeighsRefConfig;
                delete[] CauchyStress;
                delete[] hourglass_error;
                delete[] particle_dt;

                delete[] failureModel;
        }
}

/* ----------------------------------------------------------------------
 *
 * use half neighbor list to re-compute shape matrix
 *
 ---------------------------------------------------------------------- */

void PairTlsph::PreCompute() {
        tagint *mol = atom->molecule;
        double *vfrac = atom->vfrac;
        double *radius = atom->radius;
        double **x0 = atom->x0;
        double **x = atom->x;
        double **v = atom->vest; // extrapolated velocities corresponding to current positions
        double **vint = atom->v; // Velocity-Verlet algorithm velocities
        double *damage = atom->damage;
        tagint *tag = atom->tag;
        int *type = atom->type;
        int nlocal = atom->nlocal;
        int jnum, jj, i, j, itype, idim;

        tagint **partner = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->partner;
        int *npartner = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->npartner;
        float **wfd_list = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->wfd_list;
        float **wf_list = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->wf_list;
        float **degradation_ij = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->degradation_ij;
        double r0, r0Sq, wf, wfd, h, irad, voli, volj, scale, shepardWeight;
        Vector3d dx, dx0, dv, g;
        Matrix3d Ktmp, Ftmp, Fdottmp, L, U, eye;
        Vector3d vi, vj, vinti, vintj, xi, xj, x0i, x0j, dvint;
        int periodic = (domain->xperiodic || domain->yperiodic || domain->zperiodic);
        bool status;
        Matrix3d F0;

        eye.setIdentity();

        for (i = 0; i < nlocal; i++) {

                itype = type[i];
                if (setflag[itype][itype] == 1) {

                        K[i].setZero();
                        Fincr[i].setZero();
                        Fdot[i].setZero();
                        numNeighsRefConfig[i] = 0;
                        smoothVelDifference[i].setZero();
                        hourglass_error[i] = 0.0;

                        if (mol[i] < 0) { // valid SPH particle have mol > 0
                                continue;
                        }

                        // initialize aveage mass density
                        h = 2.0 * radius[i];
                        r0 = 0.0;
                        spiky_kernel_and_derivative(h, r0, domain->dimension, wf, wfd);
                        shepardWeight = wf * voli;

                        jnum = npartner[i];
                        irad = radius[i];
                        voli = vfrac[i];

                        // initialize Eigen data structures from LAMMPS data structures
                        for (idim = 0; idim < 3; idim++) {
                                xi(idim) = x[i][idim];
                                x0i(idim) = x0[i][idim];
                                vi(idim) = v[i][idim];
                                vinti(idim) = vint[i][idim];
                        }

                        for (jj = 0; jj < jnum; jj++) {

                                if (partner[i][jj] == 0)
                                        continue;
                                j = atom->map(partner[i][jj]);
                                if (j < 0) { //                 // check if lost a partner without first breaking bond
                                        partner[i][jj] = 0;
                                        continue;
                                }

                                if (mol[j] < 0) { // particle has failed. do not include it for computing any property
                                        continue;
                                }

                                if (mol[i] != mol[j]) {
                                        continue;
                                }

                                // initialize Eigen data structures from LAMMPS data structures
                                for (idim = 0; idim < 3; idim++) {
                                        xj(idim) = x[j][idim];
                                        x0j(idim) = x0[j][idim];
                                        vj(idim) = v[j][idim];
                                        vintj(idim) = vint[j][idim];
                                }
                                dx0 = x0j - x0i;
                                dx = xj - xi;

                                if (periodic)
                                        domain->minimum_image(dx0(0), dx0(1), dx0(2));

                                r0Sq = dx0.squaredNorm();
                                h = irad + radius[j];

                                r0 = sqrt(r0Sq);
                                volj = vfrac[j];

                                // distance vectors in current and reference configuration, velocity difference
                                dv = vj - vi;
                                dvint = vintj - vinti;

                                // scale the interaction according to the damage variable
                                scale = 1.0 - degradation_ij[i][jj];
                                wf = wf_list[i][jj] * scale;
                                wfd = wfd_list[i][jj] * scale;
                                g = (wfd / r0) * dx0;

                                /* build matrices */
                                Ktmp = -g * dx0.transpose();
                                Fdottmp = -dv * g.transpose();
                                Ftmp = -(dx - dx0) * g.transpose();

                                K[i] += volj * Ktmp;
                                Fdot[i] += volj * Fdottmp;
                                Fincr[i] += volj * Ftmp;
                                shepardWeight += volj * wf;
                                smoothVelDifference[i] += volj * wf * dvint;
                                numNeighsRefConfig[i]++;
                        } // end loop over j

                        // normalize average velocity field around an integration point
                        if (shepardWeight > 0.0) {
                                smoothVelDifference[i] /= shepardWeight;
                        } else {
                                smoothVelDifference[i].setZero();
                        }

                        pseudo_inverse_SVD(K[i]);
                        Fdot[i] *= K[i];
                        Fincr[i] *= K[i];
                        Fincr[i] += eye;

                        if (JAUMANN) {
                                R[i].setIdentity(); // for Jaumann stress rate, we do not need a subsequent rotation back into the reference configuration
                        } else {
                                status = PolDec(Fincr[i], R[i], U, false); // polar decomposition of the deformation gradient, F = R * U
                                if (!status) {
                                        error->message(FLERR, "Polar decomposition of deformation gradient failed.\n");
                                        mol[i] = -1;
                                } else {
                                        Fincr[i] = R[i] * U;
                                }
                        }

                        detF[i] = Fincr[i].determinant();
                        FincrInv[i] = Fincr[i].inverse();

                        // velocity gradient
                        L = Fdot[i] * FincrInv[i];

                        // symmetric (D) and asymmetric (W) parts of L
                        D[i] = 0.5 * (L + L.transpose());
                        W[i] = 0.5 * (L - L.transpose()); // spin tensor:: need this for Jaumann rate

                        // unrotated rate-of-deformation tensor d, see right side of Pronto2d, eqn.(2.1.7)
                        // convention: unrotated frame is that one, where the true rotation of an integration point has been subtracted.
                        // stress in the unrotated frame of reference is denoted sigma (stress seen by an observer doing rigid body rotations along with the material)
                        // stress in the true frame of reference (a stationary observer) is denoted by T, "true stress"
                        D[i] = (R[i].transpose() * D[i] * R[i]).eval();

                        // limit strain rate
                        //double limit = 1.0e-3 * Lookup[SIGNAL_VELOCITY][itype] / radius[i];
                        //D[i] = LimitEigenvalues(D[i], limit);

                        /*
                         * make sure F stays within some limits
                         */

                        if ((detF[i] < DETF_MIN) || (detF[i] > DETF_MAX) || (numNeighsRefConfig[i] == 0)) {
                                printf("deleting particle [" TAGINT_FORMAT "] because det(F)=%f is outside stable range %f -- %f \n", tag[i],
                                                Fincr[i].determinant(),
                                                DETF_MIN, DETF_MAX);
                                printf("nn = %d, damage=%f\n", numNeighsRefConfig[i], damage[i]);
                                cout << "Here is matrix F:" << endl << Fincr[i] << endl;
                                cout << "Here is matrix F-1:" << endl << FincrInv[i] << endl;
                                cout << "Here is matrix K-1:" << endl << K[i] << endl;
                                cout << "Here is matrix K:" << endl << K[i].inverse() << endl;
                                cout << "Here is det of K" << endl << (K[i].inverse()).determinant() << endl;
                                cout << "Here is matrix R:" << endl << R[i] << endl;
                                cout << "Here is det of R" << endl << R[i].determinant() << endl;
                                cout << "Here is matrix U:" << endl << U << endl;
                                mol[i] = -1;
                                //error->one(FLERR, "");
                        }

                        if (mol[i] < 0) {
                                D[i].setZero();
                                Fdot[i].setZero();
                                Fincr[i].setIdentity();
                                smoothVelDifference[i].setZero();
                                detF[i] = 1.0;
                                K[i].setIdentity();

                                vint[i][0] = 0.0;
                                vint[i][1] = 0.0;
                                vint[i][2] = 0.0;
                        }
                } // end loop over i
        } // end check setflag
}

/* ---------------------------------------------------------------------- */

void PairTlsph::compute(int eflag, int vflag) {

        if (atom->nmax > nmax) {
                nmax = atom->nmax;
                delete[] Fdot;
                Fdot = new Matrix3d[nmax]; // memory usage: 9 doubles
                delete[] Fincr;
                Fincr = new Matrix3d[nmax]; // memory usage: 9 doubles
                delete[] K;
                K = new Matrix3d[nmax]; // memory usage: 9 doubles
                delete[] PK1;
                PK1 = new Matrix3d[nmax]; // memory usage: 9 doubles; total 5*9=45 doubles
                delete[] detF;
                detF = new double[nmax]; // memory usage: 1 double; total 46 doubles
                delete[] smoothVelDifference;
                smoothVelDifference = new Vector3d[nmax]; // memory usage: 3 doubles; total 49 doubles
                delete[] R;
                R = new Matrix3d[nmax]; // memory usage: 9 doubles; total 67 doubles
                delete[] FincrInv;
                FincrInv = new Matrix3d[nmax]; // memory usage: 9 doubles; total 85 doubles
                delete[] W;
                W = new Matrix3d[nmax]; // memory usage: 9 doubles; total 94 doubles
                delete[] D;
                D = new Matrix3d[nmax]; // memory usage: 9 doubles; total 103 doubles
                delete[] numNeighsRefConfig;
                numNeighsRefConfig = new int[nmax]; // memory usage: 1 int; total 108 doubles
                delete[] CauchyStress;
                CauchyStress = new Matrix3d[nmax]; // memory usage: 9 doubles; total 118 doubles
                delete[] hourglass_error;
                hourglass_error = new double[nmax];
                delete[] particle_dt;
                particle_dt = new double[nmax];
        }

        if (first) { // return on first call, because reference connectivity lists still needs to be built. Also zero quantities which are otherwise undefined.
                first = false;

                for (int i = 0; i < atom->nlocal; i++) {
                        Fincr[i].setZero();
                        detF[i] = 0.0;
                        smoothVelDifference[i].setZero();
                        D[i].setZero();
                        numNeighsRefConfig[i] = 0;
                        CauchyStress[i].setZero();
                        hourglass_error[i] = 0.0;
                        particle_dt[i] = 0.0;
                }

                return;
        }

        /*
         * calculate deformations and rate-of-deformations
         */
        PairTlsph::PreCompute();

        /*
         * calculate stresses from constitutive models
         */
        PairTlsph::AssembleStress();

        /*
         * QUANTITIES ABOVE HAVE ONLY BEEN CALCULATED FOR NLOCAL PARTICLES.
         * NEED TO DO A FORWARD COMMUNICATION TO GHOST ATOMS NOW
         */
        comm->forward_comm_pair(this);

        /*
         * compute forces between particles
         */
        updateFlag = 0;
        ComputeForces(eflag, vflag);
}

void PairTlsph::ComputeForces(int eflag, int vflag) {
        tagint *mol = atom->molecule;
        double **x = atom->x;
        double **v = atom->vest;
        double **x0 = atom->x0;
        double **f = atom->f;
        double *vfrac = atom->vfrac;
        double *de = atom->de;
        double *rmass = atom->rmass;
        double *radius = atom->radius;
        double *damage = atom->damage;
        double *plastic_strain = atom->eff_plastic_strain;
        int *type = atom->type;
        int nlocal = atom->nlocal;
        int i, j, jj, jnum, itype, idim;
        double r, hg_mag, wf, wfd, h, r0, r0Sq, voli, volj;
        double delVdotDelR, visc_magnitude, deltaE, mu_ij, hg_err, gamma_dot_dx, delta, scale;
        double strain1d, strain1d_max, softening_strain, shepardWeight;
        char str[128];
        Vector3d fi, fj, dx0, dx, dv, f_stress, f_hg, dxp_i, dxp_j, gamma, g, gamma_i, gamma_j, x0i, x0j;
        Vector3d xi, xj, vi, vj, f_visc, sumForces, f_spring;
        int periodic = (domain->xperiodic || domain->yperiodic || domain->zperiodic);

        tagint **partner = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->partner;
        int *npartner = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->npartner;
        float **wfd_list = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->wfd_list;
        float **wf_list = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->wf_list;
        float **degradation_ij = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->degradation_ij;
        float **energy_per_bond = ((FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[ifix_tlsph])->energy_per_bond;
        Matrix3d eye;
        eye.setIdentity();

        ev_init(eflag, vflag);

        /*
         * iterate over pairs of particles i, j and assign forces using PK1 stress tensor
         */

        //updateFlag = 0;
        hMin = 1.0e22;
        dtRelative = 1.0e22;

        for (i = 0; i < nlocal; i++) {

                if (mol[i] < 0) {
                        continue; // Particle i is not a valid SPH particle (anymore). Skip all interactions with this particle.
                }

                itype = type[i];
                jnum = npartner[i];
                voli = vfrac[i];

                // initialize aveage mass density
                h = 2.0 * radius[i];
                r = 0.0;
                spiky_kernel_and_derivative(h, r, domain->dimension, wf, wfd);
                shepardWeight = wf * voli;

                for (idim = 0; idim < 3; idim++) {
                        x0i(idim) = x0[i][idim];
                        xi(idim) = x[i][idim];
                        vi(idim) = v[i][idim];
                }

                for (jj = 0; jj < jnum; jj++) {
                        if (partner[i][jj] == 0)
                                continue;
                        j = atom->map(partner[i][jj]);
                        if (j < 0) { //                 // check if lost a partner without first breaking bond
                                partner[i][jj] = 0;
                                continue;
                        }

                        if (mol[j] < 0) {
                                continue; // Particle j is not a valid SPH particle (anymore). Skip all interactions with this particle.
                        }

                        if (mol[i] != mol[j]) {
                                continue;
                        }

                        if (type[j] != itype) {
                                sprintf(str, "particle pair is not of same type!");
                                error->all(FLERR, str);
                        }

                        for (idim = 0; idim < 3; idim++) {
                                x0j(idim) = x0[j][idim];
                                xj(idim) = x[j][idim];
                                vj(idim) = v[j][idim];
                        }

                        if (periodic)
                                domain->minimum_image(dx0(0), dx0(1), dx0(2));

                        // check that distance between i and j (in the reference config) is less than cutoff
                        dx0 = x0j - x0i;
                        r0Sq = dx0.squaredNorm();
                        h = radius[i] + radius[j];
                        hMin = MIN(hMin, h);
                        r0 = sqrt(r0Sq);
                        volj = vfrac[j];

                        // distance vectors in current and reference configuration, velocity difference
                        dx = xj - xi;
                        dv = vj - vi;
                        r = dx.norm(); // current distance

                        // scale the interaction according to the damage variable
                        scale = 1.0 - degradation_ij[i][jj];
                        wf = wf_list[i][jj] * scale;
                        wfd = wfd_list[i][jj] * scale;

                        g = (wfd / r0) * dx0; // uncorrected kernel gradient

                        /*
                         * force contribution -- note that the kernel gradient correction has been absorbed into PK1
                         */

                        f_stress = -voli * volj * (PK1[i] + PK1[j]) * g;

                        /*
                         * artificial viscosity
                         */
                        delVdotDelR = dx.dot(dv) / (r + 0.1 * h); // project relative velocity onto unit particle distance vector [m/s]
                        LimitDoubleMagnitude(delVdotDelR, 0.01 * Lookup[SIGNAL_VELOCITY][itype]);
                        mu_ij = h * delVdotDelR / (r + 0.1 * h); // units: [m * m/s / m = m/s]
                        visc_magnitude = (-Lookup[VISCOSITY_Q1][itype] * Lookup[SIGNAL_VELOCITY][itype] * mu_ij
                                        + Lookup[VISCOSITY_Q2][itype] * mu_ij * mu_ij) / Lookup[REFERENCE_DENSITY][itype]; // units: m^5/(s^2 kg))
                        f_visc = rmass[i] * rmass[j] * visc_magnitude * wfd * dx / (r + 1.0e-2 * h); // units: kg^2 * m^5/(s^2 kg) * m^-4 = kg m / s^2 = N

                        /*
                         * hourglass deviation of particles i and j
                         */

                        gamma = 0.5 * (Fincr[i] + Fincr[j]) * dx0 - dx;
                        hg_err = gamma.norm() / r0;
                        hourglass_error[i] += volj * wf * hg_err;

                        /* SPH-like hourglass formulation */

                        if (MAX(plastic_strain[i], plastic_strain[j]) > 1.0e-3) {
                                /*
                                 * viscous hourglass formulation for particles with plastic deformation
                                 */
                                delta = gamma.dot(dx);
                                if (delVdotDelR * delta < 0.0) {
                                        hg_err = MAX(hg_err, 0.05); // limit hg_err to avoid numerical instabilities
                                        hg_mag = -hg_err * Lookup[HOURGLASS_CONTROL_AMPLITUDE][itype] * Lookup[SIGNAL_VELOCITY][itype] * mu_ij
                                                        / Lookup[REFERENCE_DENSITY][itype]; // this has units of pressure
                                } else {
                                        hg_mag = 0.0;
                                }
                                f_hg = rmass[i] * rmass[j] * hg_mag * wfd * dx / (r + 1.0e-2 * h);

                        } else {
                                /*
                                 * stiffness hourglass formulation for particle in the elastic regime
                                 */

                                gamma_dot_dx = gamma.dot(dx); // project hourglass error vector onto pair distance vector
                                LimitDoubleMagnitude(gamma_dot_dx, 0.1 * r); // limit projected vector to avoid numerical instabilities
                                delta = 0.5 * gamma_dot_dx / (r + 0.1 * h); // delta has dimensions of [m]
                                hg_mag = Lookup[HOURGLASS_CONTROL_AMPLITUDE][itype] * delta / (r0Sq + 0.01 * h * h); // hg_mag has dimensions [m^(-1)]
                                hg_mag *= -voli * volj * wf * Lookup[YOUNGS_MODULUS][itype]; // hg_mag has dimensions [J*m^(-1)] = [N]
                                f_hg = (hg_mag / (r + 0.01 * h)) * dx;
                        }

                        // scale hourglass force with damage
                        f_hg *= (1.0 - damage[i]) * (1.0 - damage[j]);

                        // sum stress, viscous, and hourglass forces
                        sumForces = f_stress + f_visc + f_hg; // + f_spring;

                        // energy rate -- project velocity onto force vector
                        deltaE = 0.5 * sumForces.dot(dv);

                        // apply forces to pair of particles
                        f[i][0] += sumForces(0);
                        f[i][1] += sumForces(1);
                        f[i][2] += sumForces(2);
                        de[i] += deltaE;

                        // tally atomistic stress tensor
                        if (evflag) {
                                ev_tally_xyz(i, j, nlocal, 0, 0.0, 0.0, sumForces(0), sumForces(1), sumForces(2), dx(0), dx(1), dx(2));
                        }

                        shepardWeight += wf * volj;

                        // check if a particle has moved too much w.r.t another particle
                        if (r > r0) {
                                if (update_method == UPDATE_CONSTANT_THRESHOLD) {
                                        if (r - r0 > update_threshold) {
                                                updateFlag = 1;
                                        }
                                } else if (update_method == UPDATE_PAIRWISE_RATIO) {
                                        if ((r - r0) / h > update_threshold) {
                                                updateFlag = 1;
                                        }
                                }
                        }

                        if (failureModel[itype].failure_max_pairwise_strain) {

                                strain1d = (r - r0) / r0;
                                strain1d_max = Lookup[FAILURE_MAX_PAIRWISE_STRAIN_THRESHOLD][itype];
                                softening_strain = 2.0 * strain1d_max;

                                if (strain1d > strain1d_max) {
                                        degradation_ij[i][jj] = (strain1d - strain1d_max) / softening_strain;
                                } else {
                                        degradation_ij[i][jj] = 0.0;
                                }

                                if (degradation_ij[i][jj] >= 1.0) { // delete interaction if fully damaged
                                        partner[i][jj] = 0;
                                }
                        }

                        if (failureModel[itype].failure_energy_release_rate) {

                                // integration approach
                                energy_per_bond[i][jj] += update->dt * f_stress.dot(dv) / (voli * volj);
                                double Vic = (2.0 / 3.0) * h * h * h; // interaction volume for 2d plane strain
                                double critical_energy_per_bond = Lookup[CRITICAL_ENERGY_RELEASE_RATE][itype] / (2.0 * Vic);

                                if (energy_per_bond[i][jj] > critical_energy_per_bond) {
                                        //degradation_ij[i][jj] = 1.0;
                                        partner[i][jj] = 0;
                                }
                        }

                        if (failureModel[itype].integration_point_wise) {

                                strain1d = (r - r0) / r0;

                                if (strain1d > 0.0) {

                                        if ((damage[i] == 1.0) && (damage[j] == 1.0)) {
                                                // check if damage_onset is already defined
                                                if (energy_per_bond[i][jj] == 0.0) { // pair damage not defined yet
                                                        energy_per_bond[i][jj] = strain1d;
                                                } else { // damage initiation strain already defined
                                                        strain1d_max = energy_per_bond[i][jj];
                                                        softening_strain = 2.0 * strain1d_max;

                                                        if (strain1d > strain1d_max) {
                                                                degradation_ij[i][jj] = (strain1d - strain1d_max) / softening_strain;
                                                        } else {
                                                                degradation_ij[i][jj] = 0.0;
                                                        }
                                                }
                                        }

                                        if (degradation_ij[i][jj] >= 1.0) { // delete interaction if fully damaged
                                                partner[i][jj] = 0;
                                        }

                                } else {
                                        degradation_ij[i][jj] = 0.0;
                                } // end failureModel[itype].integration_point_wise

                        }

                } // end loop over jj neighbors of i

                if (shepardWeight != 0.0) {
                        hourglass_error[i] /= shepardWeight;
                }

        } // end loop over i

        if (vflag_fdotr)
                virial_fdotr_compute();
}

/* ----------------------------------------------------------------------
 assemble unrotated stress tensor using deviatoric and pressure components.
 Convert to corotational Cauchy stress, then to PK1 stress and apply
 shape matrix correction
 ------------------------------------------------------------------------- */
void PairTlsph::AssembleStress() {
        tagint *mol = atom->molecule;
        double *eff_plastic_strain = atom->eff_plastic_strain;
        double *eff_plastic_strain_rate = atom->eff_plastic_strain_rate;
        double **tlsph_stress = atom->smd_stress;
        int *type = atom->type;
        double *radius = atom->radius;
        double *damage = atom->damage;
        double *rmass = atom->rmass;
        double *vfrac = atom->vfrac;
        double *e = atom->e;
        double pInitial, d_iso, pFinal, p_rate, plastic_strain_increment;
        int i, itype;
        int nlocal = atom->nlocal;
        double dt = update->dt;
        double M_eff, p_wave_speed, mass_specific_energy, vol_specific_energy, rho;
        Matrix3d sigma_rate, eye, sigmaInitial, sigmaFinal, T, T_damaged, Jaumann_rate, sigma_rate_check;
        Matrix3d d_dev, sigmaInitial_dev, sigmaFinal_dev, sigma_dev_rate, strain;
        Vector3d x0i, xi, xp;

        eye.setIdentity();
        dtCFL = 1.0e22;
        pFinal = 0.0;

        for (i = 0; i < nlocal; i++) {
                particle_dt[i] = 0.0;

                itype = type[i];
                if (setflag[itype][itype] == 1) {
                        if (mol[i] > 0) { // only do the following if particle has not failed -- mol < 0 means particle has failed

                                /*
                                 * initial stress state: given by the unrotateted Cauchy stress.
                                 * Assemble Eigen 3d matrix from stored stress state
                                 */
                                sigmaInitial(0, 0) = tlsph_stress[i][0];
                                sigmaInitial(0, 1) = tlsph_stress[i][1];
                                sigmaInitial(0, 2) = tlsph_stress[i][2];
                                sigmaInitial(1, 1) = tlsph_stress[i][3];
                                sigmaInitial(1, 2) = tlsph_stress[i][4];
                                sigmaInitial(2, 2) = tlsph_stress[i][5];
                                sigmaInitial(1, 0) = sigmaInitial(0, 1);
                                sigmaInitial(2, 0) = sigmaInitial(0, 2);
                                sigmaInitial(2, 1) = sigmaInitial(1, 2);

                                //cout << "this is sigma initial" << endl << sigmaInitial << endl;

                                pInitial = sigmaInitial.trace() / 3.0; // isotropic part of initial stress
                                sigmaInitial_dev = Deviator(sigmaInitial);
                                d_iso = D[i].trace(); // volumetric part of stretch rate
                                d_dev = Deviator(D[i]); // deviatoric part of stretch rate
                                strain = 0.5 * (Fincr[i].transpose() * Fincr[i] - eye);
                                mass_specific_energy = e[i] / rmass[i]; // energy per unit mass
                                rho = rmass[i] / (detF[i] * vfrac[i]);
                                vol_specific_energy = mass_specific_energy * rho; // energy per current volume

                                /*
                                 * pressure: compute pressure rate p_rate and final pressure pFinal
                                 */

                                ComputePressure(i, rho, mass_specific_energy, vol_specific_energy, pInitial, d_iso, pFinal, p_rate);

                                /*
                                 * material strength
                                 */

                                //cout << "this is the strain deviator rate" << endl << d_dev << endl;
                                ComputeStressDeviator(i, sigmaInitial_dev, d_dev, sigmaFinal_dev, sigma_dev_rate, plastic_strain_increment);
                                //cout << "this is the stress deviator rate" << endl << sigma_dev_rate << endl;

                                // keep a rolling average of the plastic strain rate over the last 100 or so timesteps
                                eff_plastic_strain[i] += plastic_strain_increment;

                                // compute a characteristic time over which to average the plastic strain
                                double tav = 1000 * radius[i] / (Lookup[SIGNAL_VELOCITY][itype]);
                                eff_plastic_strain_rate[i] -= eff_plastic_strain_rate[i] * dt / tav;
                                eff_plastic_strain_rate[i] += plastic_strain_increment / tav;
                                eff_plastic_strain_rate[i] = MAX(0.0, eff_plastic_strain_rate[i]);

                                /*
                                 *  assemble total stress from pressure and deviatoric stress
                                 */
                                sigmaFinal = pFinal * eye + sigmaFinal_dev; // this is the stress that is kept

                                if (JAUMANN) {
                                        /*
                                         * sigma is already the co-rotated Cauchy stress.
                                         * The stress rate, however, needs to be made objective.
                                         */

                                        if (dt > 1.0e-16) {
                                                sigma_rate = (1.0 / dt) * (sigmaFinal - sigmaInitial);
                                        } else {
                                                sigma_rate.setZero();
                                        }

                                        Jaumann_rate = sigma_rate + W[i] * sigmaInitial + sigmaInitial * W[i].transpose();
                                        sigmaFinal = sigmaInitial + dt * Jaumann_rate;
                                        T = sigmaFinal;
                                } else {
                                        /*
                                         * sigma is the unrotated stress.
                                         * need to do forward rotation of the unrotated stress sigma to the current configuration
                                         */
                                        T = R[i] * sigmaFinal * R[i].transpose();
                                }

                                /*
                                 * store unrotated stress in atom vector
                                 * symmetry is exploited
                                 */
                                tlsph_stress[i][0] = sigmaFinal(0, 0);
                                tlsph_stress[i][1] = sigmaFinal(0, 1);
                                tlsph_stress[i][2] = sigmaFinal(0, 2);
                                tlsph_stress[i][3] = sigmaFinal(1, 1);
                                tlsph_stress[i][4] = sigmaFinal(1, 2);
                                tlsph_stress[i][5] = sigmaFinal(2, 2);

                                /*
                                 *  Damage due to failure criteria.
                                 */

                                if (failureModel[itype].integration_point_wise) {
                                        ComputeDamage(i, strain, T, T_damaged);
                                        //T = T_damaged; Do not do this, it is undefined as of now
                                }

                                // store rotated, "true" Cauchy stress
                                CauchyStress[i] = T;

                                /*
                                 * We have the corotational Cauchy stress.
                                 * Convert to PK1. Note that reference configuration used for computing the forces is linked via
                                 * the incremental deformation gradient, not the full deformation gradient.
                                 */
                                PK1[i] = detF[i] * T * FincrInv[i].transpose();

                                /*
                                 * pre-multiply stress tensor with shape matrix to save computation in force loop
                                 */
                                PK1[i] = PK1[i] * K[i];

                                /*
                                 * compute stable time step according to Pronto 2d
                                 */

                                Matrix3d deltaSigma;
                                deltaSigma = sigmaFinal - sigmaInitial;
                                p_rate = deltaSigma.trace() / (3.0 * dt + 1.0e-16);
                                sigma_dev_rate = Deviator(deltaSigma) / (dt + 1.0e-16);

                                double K_eff, mu_eff;
                                effective_longitudinal_modulus(itype, dt, d_iso, p_rate, d_dev, sigma_dev_rate, damage[i], K_eff, mu_eff, M_eff);
                                p_wave_speed = sqrt(M_eff / rho);

                                if (mol[i] < 0) {
                                        error->one(FLERR, "this should not happen");
                                }

                                particle_dt[i] = 2.0 * radius[i] / p_wave_speed;
                                dtCFL = MIN(dtCFL, particle_dt[i]);

                        } else { // end if mol > 0
                                PK1[i].setZero();
                                K[i].setIdentity();
                                CauchyStress[i].setZero();
                                sigma_rate.setZero();
                                tlsph_stress[i][0] = 0.0;
                                tlsph_stress[i][1] = 0.0;
                                tlsph_stress[i][2] = 0.0;
                                tlsph_stress[i][3] = 0.0;
                                tlsph_stress[i][4] = 0.0;
                                tlsph_stress[i][5] = 0.0;
                        } // end  if mol > 0
                } // end setflag
        } // end for
}

/* ----------------------------------------------------------------------
 allocate all arrays
 ------------------------------------------------------------------------- */

void PairTlsph::allocate() {
        allocated = 1;
        int n = atom->ntypes;

        memory->create(setflag, n + 1, n + 1, "pair:setflag");
        for (int i = 1; i <= n; i++)
                for (int j = i; j <= n; j++)
                        setflag[i][j] = 0;

        memory->create(strengthModel, n + 1, "pair:strengthmodel");
        memory->create(eos, n + 1, "pair:eosmodel");
        failureModel = new failure_types[n + 1];
        memory->create(Lookup, MAX_KEY_VALUE, n + 1, "pair:LookupTable");

        memory->create(cutsq, n + 1, n + 1, "pair:cutsq"); // always needs to be allocated, even with granular neighborlist

        onerad_dynamic = new double[n + 1];
        onerad_frozen = new double[n + 1];
        maxrad_dynamic = new double[n + 1];
        maxrad_frozen = new double[n + 1];

}

/* ----------------------------------------------------------------------
 global settings
 ------------------------------------------------------------------------- */

void PairTlsph::settings(int narg, char **arg) {

        if (comm->me == 0) {
                printf(
                                "\n>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========\n");
                printf("TLSPH settings\n");
        }

        /*
         * default value for update_threshold for updates of reference configuration:
         * The maximum relative displacement which is tracked by the construction of LAMMPS' neighborlists
         * is the folowing.
         */

        cut_comm = MAX(neighbor->cutneighmax, comm->cutghostuser); // cutoff radius within which ghost atoms are communicated.
        update_threshold = cut_comm;
        update_method = UPDATE_NONE;

        int iarg = 0;

        while (true) {

                if (iarg >= narg) {
                        break;
                }

                if (strcmp(arg[iarg], "*UPDATE_CONSTANT") == 0) {
                        iarg++;
                        if (iarg == narg) {
                                error->all(FLERR, "expected number following *UPDATE_CONSTANT keyword");
                        }

                        update_method = UPDATE_CONSTANT_THRESHOLD;
                        update_threshold = force->numeric(FLERR, arg[iarg]);

                } else if (strcmp(arg[iarg], "*UPDATE_PAIRWISE") == 0) {
                        iarg++;
                        if (iarg == narg) {
                                error->all(FLERR, "expected number following *UPDATE_PAIRWISE keyword");
                        }

                        update_method = UPDATE_PAIRWISE_RATIO;
                        update_threshold = force->numeric(FLERR, arg[iarg]);

                } else {
                        char msg[128];
                        sprintf(msg, "Illegal keyword for smd/integrate_tlsph: %s\n", arg[iarg]);
                        error->all(FLERR, msg);
                }

                iarg++;
        }

        if ((update_threshold > cut_comm) && (update_method == UPDATE_CONSTANT_THRESHOLD)) {
                if (comm->me == 0) {
                        printf("\n                ***** WARNING ***\n");
                        printf("requested reference configuration update threshold is %g length units\n", update_threshold);
                        printf("This value exceeds the maximum value %g beyond which TLSPH displacements can be tracked at current settings.\n",
                                        cut_comm);
                        printf("Expect loss of neighbors!\n");
                }
        }

        if (comm->me == 0) {

                if (update_method == UPDATE_CONSTANT_THRESHOLD) {
                        printf("... will update reference configuration if magnitude of relative displacement exceeds %g length units\n",
                                        update_threshold);
                } else if (update_method == UPDATE_PAIRWISE_RATIO) {
                        printf("... will update reference configuration if ratio pairwise distance / smoothing length  exceeds %g\n",
                                        update_threshold);
                } else if (update_method == UPDATE_NONE) {
                        printf("... will never update reference configuration");
                }
                printf(
                                ">>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========\n");

        }

}

/* ----------------------------------------------------------------------
 set coeffs for one or more type pairs
 ------------------------------------------------------------------------- */

void PairTlsph::coeff(int narg, char **arg) {
        int ioffset, iarg, iNextKwd, itype;
        char str[128];
        std::string s, t;

        if (narg < 3) {
                sprintf(str, "number of arguments for pair tlsph is too small!");
                error->all(FLERR, str);
        }
        if (!allocated)
                allocate();

        /*
         * check that TLSPH parameters are given only in i,i form
         */
        if (force->inumeric(FLERR, arg[0]) != force->inumeric(FLERR, arg[1])) {
                sprintf(str, "TLSPH coefficients can only be specified between particles of same type!");
                error->all(FLERR, str);
        }
        itype = force->inumeric(FLERR, arg[0]);

// set all eos, strength and failure models to inactive by default
        eos[itype] = EOS_NONE;
        strengthModel[itype] = STRENGTH_NONE;

        if (comm->me == 0) {
                printf(
                                "\n>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========\n");
                printf("SMD / TLSPH PROPERTIES OF PARTICLE TYPE %d:\n", itype);
        }

        /*
         * read parameters which are common -- regardless of material / eos model
         */

        ioffset = 2;
        if (strcmp(arg[ioffset], "*COMMON") != 0) {
                sprintf(str, "common keyword missing!");
                error->all(FLERR, str);
        }

        t = string("*");
        iNextKwd = -1;
        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                s = string(arg[iarg]);
                if (s.compare(0, t.length(), t) == 0) {
                        iNextKwd = iarg;
                        break;
                }
        }

//printf("keyword following *COMMON is %s\n", arg[iNextKwd]);

        if (iNextKwd < 0) {
                sprintf(str, "no *KEYWORD terminates *COMMON");
                error->all(FLERR, str);
        }

        if (iNextKwd - ioffset != 7 + 1) {
                sprintf(str, "expected 7 arguments following *COMMON but got %d\n", iNextKwd - ioffset - 1);
                error->all(FLERR, str);
        }

        Lookup[REFERENCE_DENSITY][itype] = force->numeric(FLERR, arg[ioffset + 1]);
        Lookup[YOUNGS_MODULUS][itype] = force->numeric(FLERR, arg[ioffset + 2]);
        Lookup[POISSON_RATIO][itype] = force->numeric(FLERR, arg[ioffset + 3]);
        Lookup[VISCOSITY_Q1][itype] = force->numeric(FLERR, arg[ioffset + 4]);
        Lookup[VISCOSITY_Q2][itype] = force->numeric(FLERR, arg[ioffset + 5]);
        Lookup[HOURGLASS_CONTROL_AMPLITUDE][itype] = force->numeric(FLERR, arg[ioffset + 6]);
        Lookup[HEAT_CAPACITY][itype] = force->numeric(FLERR, arg[ioffset + 7]);

        Lookup[LAME_LAMBDA][itype] = Lookup[YOUNGS_MODULUS][itype] * Lookup[POISSON_RATIO][itype]
                        / ((1.0 + Lookup[POISSON_RATIO][itype]) * (1.0 - 2.0 * Lookup[POISSON_RATIO][itype]));
        Lookup[SHEAR_MODULUS][itype] = Lookup[YOUNGS_MODULUS][itype] / (2.0 * (1.0 + Lookup[POISSON_RATIO][itype]));
        Lookup[M_MODULUS][itype] = Lookup[LAME_LAMBDA][itype] + 2.0 * Lookup[SHEAR_MODULUS][itype];
        Lookup[SIGNAL_VELOCITY][itype] = sqrt(
                        (Lookup[LAME_LAMBDA][itype] + 2.0 * Lookup[SHEAR_MODULUS][itype]) / Lookup[REFERENCE_DENSITY][itype]);
        Lookup[BULK_MODULUS][itype] = Lookup[LAME_LAMBDA][itype] + 2.0 * Lookup[SHEAR_MODULUS][itype] / 3.0;

        if (comm->me == 0) {
                printf("\n material unspecific properties for SMD/TLSPH definition of particle type %d:\n", itype);
                printf("%60s : %g\n", "reference density", Lookup[REFERENCE_DENSITY][itype]);
                printf("%60s : %g\n", "Young's modulus", Lookup[YOUNGS_MODULUS][itype]);
                printf("%60s : %g\n", "Poisson ratio", Lookup[POISSON_RATIO][itype]);
                printf("%60s : %g\n", "linear viscosity coefficient", Lookup[VISCOSITY_Q1][itype]);
                printf("%60s : %g\n", "quadratic viscosity coefficient", Lookup[VISCOSITY_Q2][itype]);
                printf("%60s : %g\n", "hourglass control coefficient", Lookup[HOURGLASS_CONTROL_AMPLITUDE][itype]);
                printf("%60s : %g\n", "heat capacity [energy / (mass * temperature)]", Lookup[HEAT_CAPACITY][itype]);
                printf("%60s : %g\n", "Lame constant lambda", Lookup[LAME_LAMBDA][itype]);
                printf("%60s : %g\n", "shear modulus", Lookup[SHEAR_MODULUS][itype]);
                printf("%60s : %g\n", "bulk modulus", Lookup[BULK_MODULUS][itype]);
                printf("%60s : %g\n", "signal velocity", Lookup[SIGNAL_VELOCITY][itype]);

        }

        /*
         * read following material cards
         */

//printf("next kwd is %s\n", arg[iNextKwd]);
        eos[itype] = EOS_NONE;
        strengthModel[itype] = STRENGTH_NONE;

        while (true) {
                if (strcmp(arg[iNextKwd], "*END") == 0) {
                        if (comm->me == 0) {
                                printf("found *END keyword");
                                printf(
                                                "\n>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========>>========\n\n");
                        }
                        break;
                }

                /*
                 * Linear Elasticity model based on deformation gradient
                 */
                ioffset = iNextKwd;
                if (strcmp(arg[ioffset], "*LINEAR_DEFGRAD") == 0) {
                        strengthModel[itype] = LINEAR_DEFGRAD;

                        if (comm->me == 0) {
                                printf("reading *LINEAR_DEFGRAD\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *LINEAR_DEFGRAD");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1) {
                                sprintf(str, "expected 0 arguments following *LINEAR_DEFGRAD but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        if (comm->me == 0) {
                                printf("\n%60s\n", "Linear Elasticity model based on deformation gradient");
                        }
                } else if (strcmp(arg[ioffset], "*STRENGTH_LINEAR") == 0) {

                        /*
                         * Linear Elasticity strength only model based on strain rate
                         */

                        strengthModel[itype] = STRENGTH_LINEAR;
                        if (comm->me == 0) {
                                printf("reading *STRENGTH_LINEAR\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *STRENGTH_LINEAR");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1) {
                                sprintf(str, "expected 0 arguments following *STRENGTH_LINEAR but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        if (comm->me == 0) {
                                printf("%60s\n", "Linear Elasticity strength based on strain rate");
                        }
                } // end Linear Elasticity strength only model based on strain rate

                else if (strcmp(arg[ioffset], "*STRENGTH_LINEAR_PLASTIC") == 0) {

                        /*
                         * Linear Elastic / perfectly plastic strength only model based on strain rate
                         */

                        strengthModel[itype] = STRENGTH_LINEAR_PLASTIC;
                        if (comm->me == 0) {
                                printf("reading *STRENGTH_LINEAR_PLASTIC\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *STRENGTH_LINEAR_PLASTIC");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 2 + 1) {
                                sprintf(str, "expected 2 arguments following *STRENGTH_LINEAR_PLASTIC but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        Lookup[YIELD_STRESS][itype] = force->numeric(FLERR, arg[ioffset + 1]);
                        Lookup[HARDENING_PARAMETER][itype] = force->numeric(FLERR, arg[ioffset + 2]);

                        if (comm->me == 0) {
                                printf("%60s\n", "Linear elastic / perfectly plastic strength based on strain rate");
                                printf("%60s : %g\n", "Young's modulus", Lookup[YOUNGS_MODULUS][itype]);
                                printf("%60s : %g\n", "Poisson ratio", Lookup[POISSON_RATIO][itype]);
                                printf("%60s : %g\n", "shear modulus", Lookup[SHEAR_MODULUS][itype]);
                                printf("%60s : %g\n", "constant yield stress", Lookup[YIELD_STRESS][itype]);
                                printf("%60s : %g\n", "constant hardening parameter", Lookup[HARDENING_PARAMETER][itype]);
                        }
                } // end Linear Elastic / perfectly plastic strength only model based on strain rate

                else if (strcmp(arg[ioffset], "*JOHNSON_COOK") == 0) {

                        /*
                         * JOHNSON - COOK
                         */

                        strengthModel[itype] = STRENGTH_JOHNSON_COOK;
                        if (comm->me == 0) {
                                printf("reading *JOHNSON_COOK\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *JOHNSON_COOK");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 8 + 1) {
                                sprintf(str, "expected 8 arguments following *JOHNSON_COOK but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        Lookup[JC_A][itype] = force->numeric(FLERR, arg[ioffset + 1]);
                        Lookup[JC_B][itype] = force->numeric(FLERR, arg[ioffset + 2]);
                        Lookup[JC_a][itype] = force->numeric(FLERR, arg[ioffset + 3]);
                        Lookup[JC_C][itype] = force->numeric(FLERR, arg[ioffset + 4]);
                        Lookup[JC_epdot0][itype] = force->numeric(FLERR, arg[ioffset + 5]);
                        Lookup[JC_T0][itype] = force->numeric(FLERR, arg[ioffset + 6]);
                        Lookup[JC_Tmelt][itype] = force->numeric(FLERR, arg[ioffset + 7]);
                        Lookup[JC_M][itype] = force->numeric(FLERR, arg[ioffset + 8]);

                        if (comm->me == 0) {
                                printf("%60s\n", "Johnson Cook material strength model");
                                printf("%60s : %g\n", "A: initial yield stress", Lookup[JC_A][itype]);
                                printf("%60s : %g\n", "B : proportionality factor for plastic strain dependency", Lookup[JC_B][itype]);
                                printf("%60s : %g\n", "a : exponent for plastic strain dependency", Lookup[JC_a][itype]);
                                printf("%60s : %g\n", "C : proportionality factor for logarithmic plastic strain rate dependency",
                                                Lookup[JC_C][itype]);
                                printf("%60s : %g\n", "epdot0 : dimensionality factor for plastic strain rate dependency",
                                                Lookup[JC_epdot0][itype]);
                                printf("%60s : %g\n", "T0 : reference (room) temperature", Lookup[JC_T0][itype]);
                                printf("%60s : %g\n", "Tmelt : melting temperature", Lookup[JC_Tmelt][itype]);
                                printf("%60s : %g\n", "M : exponent for temperature dependency", Lookup[JC_M][itype]);
                        }

                } else if (strcmp(arg[ioffset], "*EOS_NONE") == 0) {

                        /*
                         * no eos
                         */

                        eos[itype] = EOS_NONE;
                        if (comm->me == 0) {
                                printf("reading *EOS_NONE\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *EOS_NONE");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1) {
                                sprintf(str, "expected 0 arguments following *EOS_NONE but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        if (comm->me == 0) {
                                printf("\n%60s\n", "no EOS selected");
                        }

                } else if (strcmp(arg[ioffset], "*EOS_LINEAR") == 0) {

                        /*
                         * linear eos
                         */

                        eos[itype] = EOS_LINEAR;
                        if (comm->me == 0) {
                                printf("reading *EOS_LINEAR\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *EOS_LINEAR");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1) {
                                sprintf(str, "expected 0 arguments following *EOS_LINEAR but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        if (comm->me == 0) {
                                printf("\n%60s\n", "linear EOS based on strain rate");
                                printf("%60s : %g\n", "bulk modulus", Lookup[BULK_MODULUS][itype]);
                        }
                } // end linear eos
                else if (strcmp(arg[ioffset], "*EOS_SHOCK") == 0) {

                        /*
                         * shock eos
                         */

                        eos[itype] = EOS_SHOCK;
                        if (comm->me == 0) {
                                printf("reading *EOS_SHOCK\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *EOS_SHOCK");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 3 + 1) {
                                sprintf(str, "expected 3 arguments (c0, S, Gamma) following *EOS_SHOCK but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        Lookup[EOS_SHOCK_C0][itype] = force->numeric(FLERR, arg[ioffset + 1]);
                        Lookup[EOS_SHOCK_S][itype] = force->numeric(FLERR, arg[ioffset + 2]);
                        Lookup[EOS_SHOCK_GAMMA][itype] = force->numeric(FLERR, arg[ioffset + 3]);
                        if (comm->me == 0) {
                                printf("\n%60s\n", "shock EOS based on strain rate");
                                printf("%60s : %g\n", "reference speed of sound", Lookup[EOS_SHOCK_C0][itype]);
                                printf("%60s : %g\n", "Hugoniot parameter S", Lookup[EOS_SHOCK_S][itype]);
                                printf("%60s : %g\n", "Grueneisen Gamma", Lookup[EOS_SHOCK_GAMMA][itype]);
                        }
                } // end shock eos

                else if (strcmp(arg[ioffset], "*EOS_POLYNOMIAL") == 0) {
                        /*
                         * polynomial eos
                         */

                        eos[itype] = EOS_POLYNOMIAL;
                        if (comm->me == 0) {
                                printf("reading *EOS_POLYNOMIAL\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *EOS_POLYNOMIAL");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 7 + 1) {
                                sprintf(str, "expected 7 arguments following *EOS_POLYNOMIAL but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        Lookup[EOS_POLYNOMIAL_C0][itype] = force->numeric(FLERR, arg[ioffset + 1]);
                        Lookup[EOS_POLYNOMIAL_C1][itype] = force->numeric(FLERR, arg[ioffset + 2]);
                        Lookup[EOS_POLYNOMIAL_C2][itype] = force->numeric(FLERR, arg[ioffset + 3]);
                        Lookup[EOS_POLYNOMIAL_C3][itype] = force->numeric(FLERR, arg[ioffset + 4]);
                        Lookup[EOS_POLYNOMIAL_C4][itype] = force->numeric(FLERR, arg[ioffset + 5]);
                        Lookup[EOS_POLYNOMIAL_C5][itype] = force->numeric(FLERR, arg[ioffset + 6]);
                        Lookup[EOS_POLYNOMIAL_C6][itype] = force->numeric(FLERR, arg[ioffset + 7]);
                        if (comm->me == 0) {
                                printf("\n%60s\n", "polynomial EOS based on strain rate");
                                printf("%60s : %g\n", "parameter c0", Lookup[EOS_POLYNOMIAL_C0][itype]);
                                printf("%60s : %g\n", "parameter c1", Lookup[EOS_POLYNOMIAL_C1][itype]);
                                printf("%60s : %g\n", "parameter c2", Lookup[EOS_POLYNOMIAL_C2][itype]);
                                printf("%60s : %g\n", "parameter c3", Lookup[EOS_POLYNOMIAL_C3][itype]);
                                printf("%60s : %g\n", "parameter c4", Lookup[EOS_POLYNOMIAL_C4][itype]);
                                printf("%60s : %g\n", "parameter c5", Lookup[EOS_POLYNOMIAL_C5][itype]);
                                printf("%60s : %g\n", "parameter c6", Lookup[EOS_POLYNOMIAL_C6][itype]);
                        }
                } // end polynomial eos

                else if (strcmp(arg[ioffset], "*FAILURE_MAX_PLASTIC_STRAIN") == 0) {

                        /*
                         * maximum plastic strain failure criterion
                         */

                        if (comm->me == 0) {
                                printf("reading *FAILURE_MAX_PLASTIC_SRTRAIN\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *FAILURE_MAX_PLASTIC_STRAIN");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1 + 1) {
                                sprintf(str, "expected 1 arguments following *FAILURE_MAX_PLASTIC_STRAIN but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        failureModel[itype].failure_max_plastic_strain = true;
                        failureModel[itype].integration_point_wise = true;
                        Lookup[FAILURE_MAX_PLASTIC_STRAIN_THRESHOLD][itype] = force->numeric(FLERR, arg[ioffset + 1]);

                        if (comm->me == 0) {
                                printf("\n%60s\n", "maximum plastic strain failure criterion");
                                printf("%60s : %g\n", "failure occurs when plastic strain reaches limit",
                                                Lookup[FAILURE_MAX_PLASTIC_STRAIN_THRESHOLD][itype]);
                        }
                } // end maximum plastic strain failure criterion
                else if (strcmp(arg[ioffset], "*FAILURE_MAX_PAIRWISE_STRAIN") == 0) {

                        /*
                         * failure criterion based on maximum strain between a pair of TLSPH particles.
                         */

                        if (comm->me == 0) {
                                printf("reading *FAILURE_MAX_PAIRWISE_STRAIN\n");
                        }

                        if (update_method != UPDATE_NONE) {
                                error->all(FLERR, "cannot use *FAILURE_MAX_PAIRWISE_STRAIN with updated Total-Lagrangian formalism");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *FAILURE_MAX_PAIRWISE_STRAIN");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1 + 1) {
                                sprintf(str, "expected 1 arguments following *FAILURE_MAX_PAIRWISE_STRAIN but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        failureModel[itype].failure_max_pairwise_strain = true;
                        failureModel[itype].integration_point_wise = true;
                        Lookup[FAILURE_MAX_PAIRWISE_STRAIN_THRESHOLD][itype] = force->numeric(FLERR, arg[ioffset + 1]);

                        if (comm->me == 0) {
                                printf("\n%60s\n", "maximum pairwise strain failure criterion");
                                printf("%60s : %g\n", "failure occurs when pairwise strain reaches limit",
                                                Lookup[FAILURE_MAX_PAIRWISE_STRAIN_THRESHOLD][itype]);
                        }
                } // end pair based maximum strain failure criterion
                else if (strcmp(arg[ioffset], "*FAILURE_MAX_PRINCIPAL_STRAIN") == 0) {
                        error->all(FLERR, "this failure model is currently unsupported");

                        /*
                         * maximum principal strain failure criterion
                         */
                        if (comm->me == 0) {
                                printf("reading *FAILURE_MAX_PRINCIPAL_STRAIN\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *FAILURE_MAX_PRINCIPAL_STRAIN");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1 + 1) {
                                sprintf(str, "expected 1 arguments following *FAILURE_MAX_PRINCIPAL_STRAIN but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        failureModel[itype].failure_max_principal_strain = true;
                        failureModel[itype].integration_point_wise = true;
                        Lookup[FAILURE_MAX_PRINCIPAL_STRAIN_THRESHOLD][itype] = force->numeric(FLERR, arg[ioffset + 1]);

                        if (comm->me == 0) {
                                printf("\n%60s\n", "maximum principal strain failure criterion");
                                printf("%60s : %g\n", "failure occurs when principal strain reaches limit",
                                                Lookup[FAILURE_MAX_PRINCIPAL_STRAIN_THRESHOLD][itype]);
                        }
                } // end maximum principal strain failure criterion
                else if (strcmp(arg[ioffset], "*FAILURE_JOHNSON_COOK") == 0) {
                        error->all(FLERR, "this failure model is currently unsupported");
                        if (comm->me == 0) {
                                printf("reading *FAILURE_JOHNSON_COOK\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *FAILURE_JOHNSON_COOK");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 5 + 1) {
                                sprintf(str, "expected 5 arguments following *FAILURE_JOHNSON_COOK but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        failureModel[itype].failure_johnson_cook = true;
                        failureModel[itype].integration_point_wise = true;

                        Lookup[FAILURE_JC_D1][itype] = force->numeric(FLERR, arg[ioffset + 1]);
                        Lookup[FAILURE_JC_D2][itype] = force->numeric(FLERR, arg[ioffset + 2]);
                        Lookup[FAILURE_JC_D3][itype] = force->numeric(FLERR, arg[ioffset + 3]);
                        Lookup[FAILURE_JC_D4][itype] = force->numeric(FLERR, arg[ioffset + 4]);
                        Lookup[FAILURE_JC_EPDOT0][itype] = force->numeric(FLERR, arg[ioffset + 5]);

                        if (comm->me == 0) {
                                printf("\n%60s\n", "Johnson-Cook failure criterion");
                                printf("%60s : %g\n", "parameter d1", Lookup[FAILURE_JC_D1][itype]);
                                printf("%60s : %g\n", "parameter d2", Lookup[FAILURE_JC_D2][itype]);
                                printf("%60s : %g\n", "parameter d3", Lookup[FAILURE_JC_D3][itype]);
                                printf("%60s : %g\n", "parameter d4", Lookup[FAILURE_JC_D4][itype]);
                                printf("%60s : %g\n", "reference plastic strain rate", Lookup[FAILURE_JC_EPDOT0][itype]);
                        }

                } else if (strcmp(arg[ioffset], "*FAILURE_MAX_PRINCIPAL_STRESS") == 0) {
                        error->all(FLERR, "this failure model is currently unsupported");

                        /*
                         * maximum principal stress failure criterion
                         */

                        if (comm->me == 0) {
                                printf("reading *FAILURE_MAX_PRINCIPAL_STRESS\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *FAILURE_MAX_PRINCIPAL_STRESS");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1 + 1) {
                                sprintf(str, "expected 1 arguments following *FAILURE_MAX_PRINCIPAL_STRESS but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        failureModel[itype].failure_max_principal_stress = true;
                        failureModel[itype].integration_point_wise = true;
                        Lookup[FAILURE_MAX_PRINCIPAL_STRESS_THRESHOLD][itype] = force->numeric(FLERR, arg[ioffset + 1]);

                        if (comm->me == 0) {
                                printf("\n%60s\n", "maximum principal stress failure criterion");
                                printf("%60s : %g\n", "failure occurs when principal stress reaches limit",
                                                Lookup[FAILURE_MAX_PRINCIPAL_STRESS_THRESHOLD][itype]);
                        }
                } // end maximum principal stress failure criterion

                else if (strcmp(arg[ioffset], "*FAILURE_ENERGY_RELEASE_RATE") == 0) {
                        if (comm->me == 0) {
                                printf("reading *FAILURE_ENERGY_RELEASE_RATE\n");
                        }

                        t = string("*");
                        iNextKwd = -1;
                        for (iarg = ioffset + 1; iarg < narg; iarg++) {
                                s = string(arg[iarg]);
                                if (s.compare(0, t.length(), t) == 0) {
                                        iNextKwd = iarg;
                                        break;
                                }
                        }

                        if (iNextKwd < 0) {
                                sprintf(str, "no *KEYWORD terminates *FAILURE_ENERGY_RELEASE_RATE");
                                error->all(FLERR, str);
                        }

                        if (iNextKwd - ioffset != 1 + 1) {
                                sprintf(str, "expected 1 arguments following *FAILURE_ENERGY_RELEASE_RATE but got %d\n", iNextKwd - ioffset - 1);
                                error->all(FLERR, str);
                        }

                        failureModel[itype].failure_energy_release_rate = true;
                        Lookup[CRITICAL_ENERGY_RELEASE_RATE][itype] = force->numeric(FLERR, arg[ioffset + 1]);

                        if (comm->me == 0) {
                                printf("\n%60s\n", "critical energy release rate failure criterion");
                                printf("%60s : %g\n", "failure occurs when energy release rate reaches limit",
                                                Lookup[CRITICAL_ENERGY_RELEASE_RATE][itype]);
                        }
                } // end energy release rate failure criterion

                else {
                  snprintf(str,128,"unknown *KEYWORD: %s", arg[ioffset]);
                  error->all(FLERR, str);
                }

        }

        setflag[itype][itype] = 1;

}

/* ----------------------------------------------------------------------
 init for one type pair i,j and corresponding j,i
 ------------------------------------------------------------------------- */

double PairTlsph::init_one(int i, int j) {

        if (!allocated)
                allocate();

        if (setflag[i][j] == 0)
                error->all(FLERR, "All pair coeffs are not set");

        if (force->newton == 1)
                error->all(FLERR, "Pair style tlsph requires newton off");

// cutoff = sum of max I,J radii for
// dynamic/dynamic & dynamic/frozen interactions, but not frozen/frozen

        double cutoff = maxrad_dynamic[i] + maxrad_dynamic[j];
        cutoff = MAX(cutoff, maxrad_frozen[i] + maxrad_dynamic[j]);
        cutoff = MAX(cutoff, maxrad_dynamic[i] + maxrad_frozen[j]);
//printf("cutoff for pair pair tlsph = %f\n", cutoff);
        return cutoff;
}

/* ----------------------------------------------------------------------
 init specific to this pair style
 ------------------------------------------------------------------------- */

void PairTlsph::init_style() {
        int i;

        if (force->newton_pair == 1) {
                error->all(FLERR, "Pair style tlsph requires newton pair off");
        }

// request a granular neighbor list
        int irequest = neighbor->request(this);
        neighbor->requests[irequest]->size = 1;

// set maxrad_dynamic and maxrad_frozen for each type
// include future Fix pour particles as dynamic

        for (i = 1; i <= atom->ntypes; i++)
                onerad_dynamic[i] = onerad_frozen[i] = 0.0;

        double *radius = atom->radius;
        int *type = atom->type;
        int nlocal = atom->nlocal;

        for (i = 0; i < nlocal; i++)
                onerad_dynamic[type[i]] = MAX(onerad_dynamic[type[i]], radius[i]);

        MPI_Allreduce(&onerad_dynamic[1], &maxrad_dynamic[1], atom->ntypes, MPI_DOUBLE, MPI_MAX, world);
        MPI_Allreduce(&onerad_frozen[1], &maxrad_frozen[1], atom->ntypes, MPI_DOUBLE, MPI_MAX, world);

// if first init, create Fix needed for storing reference configuration neighbors

        int igroup = group->find("tlsph");
        if (igroup == -1)
                error->all(FLERR, "Pair style tlsph requires its particles to be part of a group named tlsph. This group does not exist.");

        if (fix_tlsph_reference_configuration == NULL) {
                char **fixarg = new char*[3];
                fixarg[0] = (char *) "SMD_TLSPH_NEIGHBORS";
                fixarg[1] = (char *) "tlsph";
                fixarg[2] = (char *) "SMD_TLSPH_NEIGHBORS";
                modify->add_fix(3, fixarg);
                delete[] fixarg;
                fix_tlsph_reference_configuration = (FixSMD_TLSPH_ReferenceConfiguration *) modify->fix[modify->nfix - 1];
                fix_tlsph_reference_configuration->pair = this;
        }

// find associated SMD_TLSPH_NEIGHBORS fix that must exist
// could have changed locations in fix list since created

        ifix_tlsph = -1;
        for (int i = 0; i < modify->nfix; i++)
                if (strcmp(modify->fix[i]->style, "SMD_TLSPH_NEIGHBORS") == 0)
                        ifix_tlsph = i;
        if (ifix_tlsph == -1)
                error->all(FLERR, "Fix SMD_TLSPH_NEIGHBORS does not exist");

}

/* ----------------------------------------------------------------------
 neighbor callback to inform pair style of neighbor list to use
 optional granular history list
 ------------------------------------------------------------------------- */

void PairTlsph::init_list(int id, NeighList *ptr) {
        if (id == 0)
                list = ptr;
}

/* ----------------------------------------------------------------------
 memory usage of local atom-based arrays
 ------------------------------------------------------------------------- */

double PairTlsph::memory_usage() {

        return 118 * nmax * sizeof(double);
}

/* ----------------------------------------------------------------------
 extract method to provide access to this class' data structures
 ------------------------------------------------------------------------- */

void *PairTlsph::extract(const char *str, int &/*i*/) {
//printf("in PairTlsph::extract\n");
        if (strcmp(str, "smd/tlsph/Fincr_ptr") == 0) {
                return (void *) Fincr;
        } else if (strcmp(str, "smd/tlsph/detF_ptr") == 0) {
                return (void *) detF;
        } else if (strcmp(str, "smd/tlsph/PK1_ptr") == 0) {
                return (void *) PK1;
        } else if (strcmp(str, "smd/tlsph/smoothVel_ptr") == 0) {
                return (void *) smoothVelDifference;
        } else if (strcmp(str, "smd/tlsph/numNeighsRefConfig_ptr") == 0) {
                return (void *) numNeighsRefConfig;
        } else if (strcmp(str, "smd/tlsph/stressTensor_ptr") == 0) {
                return (void *) CauchyStress;
        } else if (strcmp(str, "smd/tlsph/updateFlag_ptr") == 0) {
                return (void *) &updateFlag;
        } else if (strcmp(str, "smd/tlsph/strain_rate_ptr") == 0) {
                return (void *) D;
        } else if (strcmp(str, "smd/tlsph/hMin_ptr") == 0) {
                return (void *) &hMin;
        } else if (strcmp(str, "smd/tlsph/dtCFL_ptr") == 0) {
                return (void *) &dtCFL;
        } else if (strcmp(str, "smd/tlsph/dtRelative_ptr") == 0) {
                return (void *) &dtRelative;
        } else if (strcmp(str, "smd/tlsph/hourglass_error_ptr") == 0) {
                return (void *) hourglass_error;
        } else if (strcmp(str, "smd/tlsph/particle_dt_ptr") == 0) {
                return (void *) particle_dt;
        } else if (strcmp(str, "smd/tlsph/rotation_ptr") == 0) {
                return (void *) R;
        }

        return NULL;
}

/* ---------------------------------------------------------------------- */

int PairTlsph::pack_forward_comm(int n, int *list, double *buf, int /*pbc_flag*/, int * /*pbc*/) {
        int i, j, m;
        tagint *mol = atom->molecule;
        double *damage = atom->damage;
        double *eff_plastic_strain = atom->eff_plastic_strain;
        double *eff_plastic_strain_rate = atom->eff_plastic_strain_rate;

//printf("in PairTlsph::pack_forward_comm\n");

        m = 0;
        for (i = 0; i < n; i++) {
                j = list[i];
                buf[m++] = PK1[j](0, 0); // PK1 is not symmetric
                buf[m++] = PK1[j](0, 1);
                buf[m++] = PK1[j](0, 2);
                buf[m++] = PK1[j](1, 0);
                buf[m++] = PK1[j](1, 1);
                buf[m++] = PK1[j](1, 2);
                buf[m++] = PK1[j](2, 0);
                buf[m++] = PK1[j](2, 1);
                buf[m++] = PK1[j](2, 2); // 9

                buf[m++] = Fincr[j](0, 0); // Fincr is not symmetric
                buf[m++] = Fincr[j](0, 1);
                buf[m++] = Fincr[j](0, 2);
                buf[m++] = Fincr[j](1, 0);
                buf[m++] = Fincr[j](1, 1);
                buf[m++] = Fincr[j](1, 2);
                buf[m++] = Fincr[j](2, 0);
                buf[m++] = Fincr[j](2, 1);
                buf[m++] = Fincr[j](2, 2); // 9 + 9 = 18

                buf[m++] = mol[j]; //19
                buf[m++] = damage[j]; //20
                buf[m++] = eff_plastic_strain[j]; //21
                buf[m++] = eff_plastic_strain_rate[j]; //22

        }
        return m;
}

/* ---------------------------------------------------------------------- */

void PairTlsph::unpack_forward_comm(int n, int first, double *buf) {
        int i, m, last;
        tagint *mol = atom->molecule;
        double *damage = atom->damage;
        double *eff_plastic_strain = atom->eff_plastic_strain;
        double *eff_plastic_strain_rate = atom->eff_plastic_strain_rate;

//printf("in PairTlsph::unpack_forward_comm\n");

        m = 0;
        last = first + n;
        for (i = first; i < last; i++) {

                PK1[i](0, 0) = buf[m++]; // PK1 is not symmetric
                PK1[i](0, 1) = buf[m++];
                PK1[i](0, 2) = buf[m++];
                PK1[i](1, 0) = buf[m++];
                PK1[i](1, 1) = buf[m++];
                PK1[i](1, 2) = buf[m++];
                PK1[i](2, 0) = buf[m++];
                PK1[i](2, 1) = buf[m++];
                PK1[i](2, 2) = buf[m++];

                Fincr[i](0, 0) = buf[m++];
                Fincr[i](0, 1) = buf[m++];
                Fincr[i](0, 2) = buf[m++];
                Fincr[i](1, 0) = buf[m++];
                Fincr[i](1, 1) = buf[m++];
                Fincr[i](1, 2) = buf[m++];
                Fincr[i](2, 0) = buf[m++];
                Fincr[i](2, 1) = buf[m++];
                Fincr[i](2, 2) = buf[m++];

                mol[i] = static_cast<int>(buf[m++]);
                damage[i] = buf[m++];
                eff_plastic_strain[i] = buf[m++]; //22
                eff_plastic_strain_rate[i] = buf[m++]; //23
        }
}

/* ----------------------------------------------------------------------
 compute effective P-wave speed
 determined by longitudinal modulus
 ------------------------------------------------------------------------- */

void PairTlsph::effective_longitudinal_modulus(const int itype, const double dt, const double d_iso, const double p_rate,
                const Matrix3d d_dev, const Matrix3d sigma_dev_rate, const double /*damage*/, double &K_eff, double &mu_eff, double &M_eff) {
        double M0; // initial longitudinal modulus
        double shear_rate_sq;

//      if (damage >= 0.5) {
//              M_eff = Lookup[M_MODULUS][itype];
//              K_eff = Lookup[BULK_MODULUS][itype];
//              mu_eff = Lookup[SHEAR_MODULUS][itype];
//              return;
//      }

        M0 = Lookup[M_MODULUS][itype];

        if (dt * d_iso > 1.0e-6) {
                K_eff = p_rate / d_iso;
                if (K_eff < 0.0) { // it is possible for K_eff to become negative due to strain softening
//                      if (damage == 0.0) {
//                              error->one(FLERR, "computed a negative effective bulk modulus but particle is not damaged.");
//                      }
                        K_eff = Lookup[BULK_MODULUS][itype];
                }
        } else {
                K_eff = Lookup[BULK_MODULUS][itype];
        }

        if (domain->dimension == 3) {
// Calculate 2 mu by looking at ratio shear stress / shear strain. Use numerical softening to avoid divide-by-zero.
                mu_eff = 0.5
                                * (sigma_dev_rate(0, 1) / (d_dev(0, 1) + 1.0e-16) + sigma_dev_rate(0, 2) / (d_dev(0, 2) + 1.0e-16)
                                                + sigma_dev_rate(1, 2) / (d_dev(1, 2) + 1.0e-16));

// Calculate magnitude of deviatoric strain rate. This is used for deciding if shear modulus should be computed from current rate or be taken as the initial value.
                shear_rate_sq = d_dev(0, 1) * d_dev(0, 1) + d_dev(0, 2) * d_dev(0, 2) + d_dev(1, 2) * d_dev(1, 2);
        } else {
                mu_eff = 0.5 * (sigma_dev_rate(0, 1) / (d_dev(0, 1) + 1.0e-16));
                shear_rate_sq = d_dev(0, 1) * d_dev(0, 1);
        }

        if (dt * dt * shear_rate_sq < 1.0e-8) {
                mu_eff = Lookup[SHEAR_MODULUS][itype];
        }

        if (mu_eff < Lookup[SHEAR_MODULUS][itype]) { // it is possible for mu_eff to become negative due to strain softening
//              if (damage == 0.0) {
//                      printf("mu_eff = %f, tau=%f, gamma=%f\n", mu_eff, sigma_dev_rate(0, 1), d_dev(0, 1));
//                      error->message(FLERR, "computed a negative effective shear modulus but particle is not damaged.");
//              }
                mu_eff = Lookup[SHEAR_MODULUS][itype];
        }

//mu_eff = Lookup[SHEAR_MODULUS][itype];

        if (K_eff < 0.0) {
                printf("K_eff = %f, p_rate=%f, vol_rate=%f\n", K_eff, p_rate, d_iso);
        }

        if (mu_eff < 0.0) {
                printf("mu_eff = %f, tau=%f, gamma=%f\n", mu_eff, sigma_dev_rate(0, 1), d_dev(0, 1));
                error->one(FLERR, "");
        }

        M_eff = (K_eff + 4.0 * mu_eff / 3.0); // effective dilational modulus, see Pronto 2d eqn 3.4.8

        if (M_eff < M0) { // do not allow effective dilatational modulus to decrease beyond its initial value
                M_eff = M0;
        }
}

/* ----------------------------------------------------------------------
 compute pressure. Called from AssembleStress().
 ------------------------------------------------------------------------- */
void PairTlsph::ComputePressure(const int i, const double rho, const double mass_specific_energy, const double vol_specific_energy,
        const double pInitial, const double d_iso, double &pFinal, double &p_rate) {
        int *type = atom->type;
        double dt = update->dt;

        int itype;

        itype = type[i];

        switch (eos[itype]) {
        case EOS_LINEAR:
                LinearEOS(Lookup[BULK_MODULUS][itype], pInitial, d_iso, dt, pFinal, p_rate);
                break;
        case EOS_NONE:
                pFinal = 0.0;
                p_rate = 0.0;
                break;
        case EOS_SHOCK:
//  rho,  rho0,  e,  e0,  c0,  S,  Gamma,  pInitial,  dt,  &pFinal,  &p_rate);
                ShockEOS(rho, Lookup[REFERENCE_DENSITY][itype], mass_specific_energy, 0.0, Lookup[EOS_SHOCK_C0][itype],
                                Lookup[EOS_SHOCK_S][itype], Lookup[EOS_SHOCK_GAMMA][itype], pInitial, dt, pFinal, p_rate);
                break;
        case EOS_POLYNOMIAL:
                polynomialEOS(rho, Lookup[REFERENCE_DENSITY][itype], vol_specific_energy, Lookup[EOS_POLYNOMIAL_C0][itype],
                                Lookup[EOS_POLYNOMIAL_C1][itype], Lookup[EOS_POLYNOMIAL_C2][itype], Lookup[EOS_POLYNOMIAL_C3][itype],
                                Lookup[EOS_POLYNOMIAL_C4][itype], Lookup[EOS_POLYNOMIAL_C5][itype], Lookup[EOS_POLYNOMIAL_C6][itype], pInitial, dt,
                                pFinal, p_rate);

                break;
        default:
                error->one(FLERR, "unknown EOS.");
                break;
        }
}

/* ----------------------------------------------------------------------
 Compute stress deviator. Called from AssembleStress().
 ------------------------------------------------------------------------- */
void PairTlsph::ComputeStressDeviator(const int i, const Matrix3d sigmaInitial_dev, const Matrix3d d_dev, Matrix3d &sigmaFinal_dev,
                Matrix3d &sigma_dev_rate, double &plastic_strain_increment) {
        double *eff_plastic_strain = atom->eff_plastic_strain;
        double *eff_plastic_strain_rate = atom->eff_plastic_strain_rate;
        int *type = atom->type;
        double *rmass = atom->rmass;
//double *vfrac = atom->vfrac;
        double *e = atom->e;
        double dt = update->dt;
        double yieldStress;
        int itype;

        double mass_specific_energy = e[i] / rmass[i]; // energy per unit mass
        plastic_strain_increment = 0.0;
        itype = type[i];

        switch (strengthModel[itype]) {
        case STRENGTH_LINEAR:

                sigma_dev_rate = 2.0 * Lookup[SHEAR_MODULUS][itype] * d_dev;
                sigmaFinal_dev = sigmaInitial_dev + dt * sigma_dev_rate;

                break;
        case LINEAR_DEFGRAD:
//LinearStrengthDefgrad(Lookup[LAME_LAMBDA][itype], Lookup[SHEAR_MODULUS][itype], Fincr[i], &sigmaFinal_dev);
//eff_plastic_strain[i] = 0.0;
//p_rate = pInitial - sigmaFinal_dev.trace() / 3.0;
//sigma_dev_rate = sigmaInitial_dev - Deviator(sigmaFinal_dev);
                error->one(FLERR, "LINEAR_DEFGRAD is only for debugging purposes and currently deactivated.");
                R[i].setIdentity();
                break;
        case STRENGTH_LINEAR_PLASTIC:

                yieldStress = Lookup[YIELD_STRESS][itype] + Lookup[HARDENING_PARAMETER][itype] * eff_plastic_strain[i];
                LinearPlasticStrength(Lookup[SHEAR_MODULUS][itype], yieldStress, sigmaInitial_dev, d_dev, dt, sigmaFinal_dev,
                                sigma_dev_rate, plastic_strain_increment);
                break;
        case STRENGTH_JOHNSON_COOK:
                JohnsonCookStrength(Lookup[SHEAR_MODULUS][itype], Lookup[HEAT_CAPACITY][itype], mass_specific_energy, Lookup[JC_A][itype],
                                Lookup[JC_B][itype], Lookup[JC_a][itype], Lookup[JC_C][itype], Lookup[JC_epdot0][itype], Lookup[JC_T0][itype],
                                Lookup[JC_Tmelt][itype], Lookup[JC_M][itype], dt, eff_plastic_strain[i], eff_plastic_strain_rate[i],
                                sigmaInitial_dev, d_dev, sigmaFinal_dev, sigma_dev_rate, plastic_strain_increment);
                break;
        case STRENGTH_NONE:
                sigmaFinal_dev.setZero();
                sigma_dev_rate.setZero();
                break;
        default:
                error->one(FLERR, "unknown strength model.");
                break;
        }

}

/* ----------------------------------------------------------------------
 Compute damage. Called from AssembleStress().
 ------------------------------------------------------------------------- */
void PairTlsph::ComputeDamage(const int i, const Matrix3d strain, const Matrix3d stress, Matrix3d &/*stress_damaged*/) {
        double *eff_plastic_strain = atom->eff_plastic_strain;
        double *eff_plastic_strain_rate = atom->eff_plastic_strain_rate;
        double *radius = atom->radius;
        double *damage = atom->damage;
        int *type = atom->type;
        int itype = type[i];
        double jc_failure_strain;
//double damage_gap, damage_rate;
        Matrix3d eye, stress_deviator;

        eye.setIdentity();
        stress_deviator = Deviator(stress);
        double pressure = -stress.trace() / 3.0;

        if (failureModel[itype].failure_max_principal_stress) {
                error->one(FLERR, "not yet implemented");
                /*
                 * maximum stress failure criterion:
                 */
                IsotropicMaxStressDamage(stress, Lookup[FAILURE_MAX_PRINCIPAL_STRESS_THRESHOLD][itype]);
        } else if (failureModel[itype].failure_max_principal_strain) {
                error->one(FLERR, "not yet implemented");
                /*
                 * maximum strain failure criterion:
                 */
                IsotropicMaxStrainDamage(strain, Lookup[FAILURE_MAX_PRINCIPAL_STRAIN_THRESHOLD][itype]);
        } else if (failureModel[itype].failure_max_plastic_strain) {
                if (eff_plastic_strain[i] >= Lookup[FAILURE_MAX_PLASTIC_STRAIN_THRESHOLD][itype]) {
                        damage[i] = 1.0;
                        //double damage_gap = 0.5 * Lookup[FAILURE_MAX_PLASTIC_STRAIN_THRESHOLD][itype];
                        //damage[i] = (eff_plastic_strain[i] - Lookup[FAILURE_MAX_PLASTIC_STRAIN_THRESHOLD][itype]) / damage_gap;
                }
        } else if (failureModel[itype].failure_johnson_cook) {

                //cout << "this is stress deviator" << stress_deviator << endl;

                jc_failure_strain = JohnsonCookFailureStrain(pressure, stress_deviator, Lookup[FAILURE_JC_D1][itype],
                                Lookup[FAILURE_JC_D2][itype], Lookup[FAILURE_JC_D3][itype], Lookup[FAILURE_JC_D4][itype],
                                Lookup[FAILURE_JC_EPDOT0][itype], eff_plastic_strain_rate[i]);

                //cout << "plastic strain increment is " << plastic_strain_increment << "  jc fs is " << jc_failure_strain << endl;
                //printf("JC failure strain is: %f\n", jc_failure_strain);

                if (eff_plastic_strain[i] >= jc_failure_strain) {
                        double damage_rate = Lookup[SIGNAL_VELOCITY][itype] / (100.0 * radius[i]);
                        damage[i] += damage_rate * update->dt;
                        //damage[i] = 1.0;
                }
        }

        /*
         * Apply damage to integration point
         */

//      damage[i] = MIN(damage[i], 0.8);
//
//      if (pressure > 0.0) { // compression: particle can carry compressive load but reduced shear
//              stress_damaged = -pressure * eye + (1.0 - damage[i]) * Deviator(stress);
//      } else { // tension: particle has reduced tensile and shear load bearing capability
//              stress_damaged = (1.0 - damage[i]) * (-pressure * eye + Deviator(stress));
//      }

}