grass.script: Add nprocs to raster.mapcalc function #6580
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With this change, callers of gs.mapcalc can now use nprocs to set number of processes for the underlying r.mapcalc. This makes it available to a number of Python tools which use gs.mapcalc to call r.mapcalc (as well as to user scripts). The default is set to 1. Specifically, the parameter default is None which is translated to 1 as opposed to using r.mapcalc's default. As a result, r.mapcalc's default is now independent from the default of gs.mapcalc. At this point, it makes all the Python calls using gs.mapcalc behave as before, i.e., one core only, while direct usage of r.mapcalc uses the all-cores default as do the other C tools now. See also OSGeo#6564 (discussion on default for r.mapcalc), OSGeo#5731 (default for nprocs in C), and OSGeo#5742 (r.mapcalc OpenMP version).
This was referenced Nov 5, 2025
ninsbl
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Nov 5, 2025
wenzeslaus
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One of the two steps in r.grow is using r.mapcalc. This allows user to control the number of cores used by r.mapcalc in that step (#5742). This is more critical with the default being all cores (#5731) even if the impact is possibly limited given that the main step is not parallelized. This depends on #6580 for the nprocs parameter in the gs.mapcalc function.
wenzeslaus
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With r.mapcalc being parallel (#5742) and the default nprocs in C (for r.mapcalc) being all cores (#5731), it both makes sense and is necessary to have a pass-through nprocs in r.mapcalc.simple. This gives users access to the parallelization options (regardless of the default), and it allows users to avoid oversubscription (with the default being all cores). This depends on #6580 for the nprocs parameter in the gs.mapcalc function.
wenzeslaus
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The i.image.mosaic tool uses r.mapcalc for the main processing step. This allows user to control the number of cores used by r.mapcalc (since OpenMP parallelization was added to r.mapcalc in #5742). With the default number of cores used for processing being all cores (#5731), the parallelization is enabled by default. This allows users to control number of cores used allowing for specific number of cores to be used. This depends on #6580 for the nprocs parameter in the gs.mapcalc function.
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With this change, callers of gs.mapcalc can now use nprocs to set number of processes for the underlying r.mapcalc. This makes it available to a number of Python tools which use gs.mapcalc to call r.mapcalc (as well as to user scripts).
The default is set to 1. Specifically, the parameter default is None which is translated to 1 as opposed to using r.mapcalc's default. As a result, r.mapcalc's default is now independent from the default of gs.mapcalc. At this point, it makes all the Python calls using gs.mapcalc behave as before, i.e., one core only, while direct usage of r.mapcalc uses the all-cores default as do the other C tools now.
See also #6564 (discussion on default for r.mapcalc), #5731 (default for nprocs in C), and #5742 (r.mapcalc OpenMP version).