Added speed tricks in description of mcmc_negfc_sampling
@@ -376,6 +376,17 @@ def mcmc_negfc_sampling(cube, angs, psfn, ncomp, plsc, initial_state, fwhm=4,
See description of ``mu_sigma`` and ``sigma`` for more details on
:math:`\sigma`.
+ *Speed tricks*:
+ - crop your input cube to a size such as to just include the annulus on\
+ which the PCA is performed;
+ - set `imlib='opencv'` (much faster image rotations, BUT at the expense\
+ of flux conservation);
+ - increase `nproc` (if your machine allows);
+ - reduce `ac_c` (or increase `rhat_threshold` if `conv_test='gb'`) for\
+ a faster convergence);
+ - reduce `niteration_limit` to force the sampler to stop even if it has\
+ not reached convergence.
+
Parameters
----------
cube: numpy.array
