Add description of env vars for parallel build and auto cc detection
@@ -82,23 +82,29 @@ For installation
These environment variables are used during installation (building CuPy from source).
-+-----------------------------+----------------------------------------------------------------+
++------------------------------+----------------------------------------------------------------+
| ``CUDA_PATH`` | See the description above. |
-+-----------------------------+----------------------------------------------------------------+
++------------------------------+----------------------------------------------------------------+
| ``CUTENSOR_PATH`` | Path to the cuTENSOR root directory that contains ``lib`` and |
| | ``include`` directories. (experimental) |
-+-----------------------------+----------------------------------------------------------------+
++------------------------------+----------------------------------------------------------------+
| ``NVCC`` | Define the compiler to use when compiling CUDA files. |
-+-----------------------------+----------------------------------------------------------------+
++------------------------------+----------------------------------------------------------------+
| ``CUPY_PYTHON_350_FORCE`` | Enforce CuPy to be installed against Python 3.5.0 (not |
| | recommended). |
-+-----------------------------+----------------------------------------------------------------+
++------------------------------+----------------------------------------------------------------+
| ``CUPY_INSTALL_USE_HIP`` | For building the ROCm support, see :ref:`install_hip` for |
| | further detail. |
-+-----------------------------+----------------------------------------------------------------+
++------------------------------+----------------------------------------------------------------+
| ``CUPY_NVCC_GENERATE_CODE`` | To build CuPy for a particular CUDA architecture. For example, |
| | ``CUPY_NVCC_GENERATE_CODE="arch=compute_60,code=sm_60"``. For |
| | specifying multiple archs, concatenate the ``arch=...`` strings|
-| | with semicolons (``;``). When this is not set, the default is |
-| | to support all architectures. |
-+-----------------------------+----------------------------------------------------------------+
+| | with semicolons (``;``). If ``current`` is specified, then |
+| | it will automatically detect the currently installed GPU |
+| | architectures in build time. When this is not set, |
+| | the default is to support all architectures. |
++------------------------------+----------------------------------------------------------------+
+| ``CUPY_CUPY_NUM_BUILD_JOBS`` | To enable or disable parallel build, sets the number of |
+| | processes used to build the extensions in parallel. Defaults |
+| | to ``4``
++------------------------------+----------------------------------------------------------------+
