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Merge topic 'patch-ProcessorCount'

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9e40bd860f ProcessorCount: Update documentation

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !10407
This commit is contained in:
Brad King 2025-03-04 13:48:08 +00:00 committed by Kitware Robot
commit 213ea8a752
4 changed files with 45 additions and 38 deletions
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2
Modules/CMakeFindCodeBlocks.cmake
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@ -18,7 +18,7 @@ include(${CMAKE_CURRENT_LIST_DIR}/CMakeExtraGeneratorDetermineCompilerMacrosAndI
set(_CMAKE_CODEBLOCKS_INITIAL_MAKE_ARGS "")
include(ProcessorCount)
processorcount(_CMAKE_CODEBLOCKS_PROCESSOR_COUNT)
ProcessorCount(_CMAKE_CODEBLOCKS_PROCESSOR_COUNT)
# Only set -j if we are under UNIX and if the make-tool used actually has "make" in the name
# (we may also get here in the future e.g. for ninja)

2
Modules/CMakeFindEclipseCDT4.cmake
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@ -68,7 +68,7 @@ _find_eclipse_version()
set(_CMAKE_ECLIPSE_INITIAL_MAKE_ARGS "")
include(ProcessorCount)
processorcount(_CMAKE_ECLIPSE_PROCESSOR_COUNT)
ProcessorCount(_CMAKE_ECLIPSE_PROCESSOR_COUNT)
# Only set -j if we are under UNIX and if the make-tool used actually has "make" in the name
# (we may also get here in the future e.g. for ninja)

2
Modules/CMakeFindKate.cmake
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@ -9,7 +9,7 @@
# Try to find out how many CPUs we have and set the -j argument for make accordingly
include(ProcessorCount)
processorcount(_CMAKE_KATE_PROCESSOR_COUNT)
ProcessorCount(_CMAKE_KATE_PROCESSOR_COUNT)
# Only set -j if we are under UNIX and if the make-tool used actually has "make" in the name
# (we may also get here in the future e.g. for ninja)

77
Modules/ProcessorCount.cmake
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@ -5,49 +5,56 @@
ProcessorCount
--------------
ProcessorCount(var)
This module provides the following function to determine the number of
processors/cores:
Determine the number of processors/cores and save value in ${var}
.. command:: ProcessorCount
Sets the variable named ${var} to the number of physical cores
available on the machine if the information can be determined.
Otherwise it is set to 0. Currently this functionality is implemented
for AIX, cygwin, FreeBSD, HPUX, Linux, macOS, QNX, Sun and
Windows.
.. code-block:: cmake
.. versionchanged:: 3.15
On Linux, returns the container CPU count instead of the host CPU count.
ProcessorCount(<variable>)
This function is guaranteed to return a positive integer (>=1) if it
succeeds. It returns 0 if there's a problem determining the processor
count.
Sets a local variable named ``<variable>`` to the number of logical CPU cores
available on the machine, if the information can be determined. If
successful, the variable is guaranteed to be set to a positive integer (>=1).
If the processor count cannot be determined, it is set to 0.
More generally accurate physical CPU count can be obtained via
:command:`cmake_host_system_information`:
Currently, this functionality is implemented for AIX, Cygwin, FreeBSD, Haiku,
HPUX, Linux, macOS, QNX, Sun and Windows.
This function provides an approximation of the number of compute cores
available on the current machine, making it useful for parallel building and
testing. It is meant to help utilize as much of the machine as seems
reasonable, though users should consider other workloads running on the
machine before using its full capacity for parallel tasks.
.. versionchanged:: 3.15
On Linux, returns the container CPU count instead of the host CPU count.
.. note::
This module relies on system-dependent commands to determine the number of
processors, which may not always provide accurate information in certain
environments. A more generally accurate logical CPU count can be also
obtained with the :command:`cmake_host_system_information`:
.. code-block:: cmake
cmake_host_system_information(RESULT n QUERY NUMBER_OF_LOGICAL_CORES)
Examples
^^^^^^^^
Using ``ProcessorCount`` module in a :option:`ctest -S` dashboard script:
.. code-block:: cmake
cmake_host_system_information(RESULT N
QUERY NUMBER_OF_PHYSICAL_CORES)
Example use, in a ctest -S dashboard script:
.. code-block:: cmake
include(ProcessorCount)
ProcessorCount(N)
if(NOT N EQUAL 0)
set(CTEST_BUILD_FLAGS -j${N})
set(ctest_test_args ${ctest_test_args} PARALLEL_LEVEL ${N})
endif()
This function is intended to offer an approximation of the value of
the number of compute cores available on the current machine, such
that you may use that value for parallel building and parallel
testing. It is meant to help utilize as much of the machine as seems
reasonable. Of course, knowledge of what else might be running on the
machine simultaneously should be used when deciding whether to request
a machine's full capacity all for yourself.
include(ProcessorCount)
ProcessorCount(n)
if(NOT n EQUAL 0)
set(CTEST_BUILD_FLAGS -j${n})
set(ctest_test_args ${ctest_test_args} PARALLEL_LEVEL ${n})
endif()
#]=======================================================================]
# A more reliable way might be to compile a small C program that uses the CPUID