C.3.2 num-comps-file, num-build-cpus, and compilation time

If the build system has multiple processors, you can split the build to share it out.

The value for num-build-cpus sets the maximum number of groups of files to split the build into. Have one group for each build system processor in order to fully use each processor. This makes the build quicker. The value for num-comps-file sets the maximum number of components per C++ file.
For example, if there are 40 components, num-build-cpus is set to 4, and num-comps-file is set to 25, then SimGen produces four groups of files, each with 10 components. This is less than num-comps-file, so each group contains only one C++ file. So:
  • SimGen produces four C++ files.
  • Each C++ file has 10 components instead of the maximum value of 25.
    Using only the num-comps-file option to calculate the components per file would result in two C++ files, with one file containing 25 components and the second file containing 15. This split would only use two build system processors. Accurately setting num-build-cpus allows SimGen to fully use all processors.
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