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grass.script: Add available_cpus and resolve_nprocs helpers - #7414
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Affinity-aware CPU count and G_OPT_M_NPROCS resolution (positive as-is, 0 = all cores, negative reserves cores). Migrate ad-hoc cpu_count() sites in pygrass, jupyter, animation, and datacatalog GUI to the new helpers; all become container/cgroup aware. Fix t.rast.univar and t.rast3d.univar: nprocs=0 was silently clamped to 1 instead of using all available cores. New in grass.script public API in GRASS 8.6.
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I had these minor comments pending. Please, consider them for your next related PR.
| :param nprocs: The maximum number of Module processes that can be | ||
| run in parallel. A positive value is used as-is, | ||
| ``0`` or ``None`` means use all available CPUs, and | ||
| a negative value reserves that many CPUs (clamped |
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This is.not clear. I don't see how it explains the behavior.
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| Mirrors the semantics of ``G_set_omp_num_threads()`` in | ||
| ``lib/gis/omp_threads.c``: 0 means use all available cores, a positive | ||
| number is used as-is, a negative number means cpu_count + nprocs |
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This is correct, but maybe also explaining the actual usage would be helpful (keep that many available, use the rest).
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Affinity-aware CPU count and G_OPT_M_NPROCS resolution (positive as-is, 0 = all cores, negative reserves cores). Migrate ad-hoc cpu_count() sites in pygrass, jupyter, animation, and datacatalog GUI to the new helpers; all become container/cgroup aware. Fix t.rast.univar and t.rast3d.univar: nprocs=0 was silently clamped to 1 instead of using all available cores. New in grass.script public API in GRASS 8.6.
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We are using
G_set_omp_num_threadsthat resolves nprocs <= 0, but in Python, we don't have equivalent, potentially resulting in bugs. This PR adds the function for resolving the nprocs and also function for getting available cpus that works better in containers.available_cpus()— number of CPUs this process may actually use. Prefers affinity-aware sources(
os.process_cpu_counton 3.13+,os.sched_getaffinityon Linux) overos.cpu_count, which reports the host totaland overcounts in containers and cgroup-limited jobs.
resolve_nprocs(nprocs)— mirrorsG_set_omp_num_threads()inlib/gis/omp_threads.c:0→ all available coresavailable + nprocs, clamped to at least 1These functions are applied in the code base, resulting in some bug fixes:
t.rast.univar/t.rast3d.univar:nprocs=0(documented as "use all available cores") was silently clamped to 1, so the tool ran serially. The tool entry points now applygs.resolve_nprocs()so the documentedG_OPT_M_NPROCSsemantics take effect for0and negative values.AI-assisted (Claude Code) — used for migration planning, edge case analysis, and drafting docstrings and tests.