24655, "bradcray", "Homebrew on Mac M1/M2 systems computes misleading 'here.maxTaskPar' values", "2024-03-20T17:19:07Z"
While testing writeln(here.maxTaskPar); on my M1 Mac using homebrew, I was surprised to see it report 10 as the result rather than 8. I do see 8 when using a compiler built from source.
My understanding is that this is because:
- the Mac has 8 performance cores and 2 efficiency cores
- homebrew is currently built without
hwlocsupport, so we don't distinguish between them as we do whenhwlocis enabled
And for additional context:
hwlocdefaults tononewhen usingCHPL_TASKS=fifo- the explanation for why we use
fifoby default is given here: Homebrew formula: use cstdlib and fifo tasks by stonea · Pull Request #23415 · chapel-lang/chapel · GitHub - Elliot tried to enable system versions of
hwlocin the homebrew environment in Fix support for using a system hwloc and jemalloc by ronawho · Pull Request #23409 · chapel-lang/chapel · GitHub