6. Compiling GSAS-II¶
A small amount of GSAS-II code is written in Fortran and one routine in C, rather than Python, to provide improved computation speed. Other large and complex capabilities, such as the GSAS(-I) space group interpretation code and DIFFaX are also used as as Fortran code. This code must be compiled before it is run. Normally this is done for you, but on occasion it must be done locally.
The supplied binaries are placed in a subdirectory name with name prefix_pX.X_nY.Y where prefix is noted below and X.X is the Python version and Y.Y is the numpy
Windows-10: 64-bit Intel-compatible processors. [Prefix win_64_]
MacOS: Intel processors. [Prefix mac_64_]
MacOS: ARM processors, aka Apple Silicon (M1, etc). [Prefix mac_arm_]
Linux: 64-bit Intel-compatible processors. [Prefix linux_64_]
Linux: ARM processors (64-bit and 32-bit Raspberry Pi OS only). [Prefixes linux_arm32_ and linux_arm64_]
Some older versions combinations of Python and NumPy can be found in the older svn repository for GSAS-II: https://subversion.xray.aps.anl.gov/trac/pyGSAS/browser/Binaries
The compilation process requires installation of the gcc and gfortran compilers. Others may be possible, but have not been tried. Also, the Python Scons package must be installed into Python. compilation is done with commands:
cd fsource
scons
The scons file captures the compilation options needed for the supported platforms, but to compile on other platforms, it may be necessary to modify the Sconstruct file to configure for the new platform.
Installation of compilers is highly depend on the computer system being used, but in many cases they can be installed as a conda package, with a command such as:
conda install gfortran_osx-64 scons
Use the conda search gfortran command to find the name for the package.
On most linux systems, one can use a command such as sudo apt-get gfortran or yum install gcc-gfortran. Also see https://gcc.gnu.org/wiki/GFortranBinaries for more information.
Note that the intent is that this Scons-based process will be replaced with one to run under meson in mid-2024. In the meantime, some older web pages discussing compiling GSAS-II may be of use: