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# - ProcessorCount(var)
# Determine the number of processors/cores and save value in ${var}
#
# Sets the variable named ${var} to the number of physical cores available on
# the machine if the information can be determined. Otherwise it is set to 0.
# Currently this functionality is only implemented for Windows, Mac OS X and
# Unix systems providing getconf or the /proc/cpuinfo interface (e.g. Linux).
# A more reliable way might be to compile a small C program that uses the CPUID
# instruction, but that again requires compiler support or compiling assembler
# code.
#=============================================================================
# Copyright 2010 Kitware, Inc.
#
# Distributed under the OSI-approved BSD License (the "License");
# see accompanying file Copyright.txt for details.
#
# This software is distributed WITHOUT ANY WARRANTY; without even the
# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the License for more information.
#=============================================================================
# (To distribute this file outside of CMake, substitute the full
# License text for the above reference.)
function(ProcessorCount var)
# Unknown:
set(count 0)
if(WIN32)
# Windows:
set(count "$ENV{NUMBER_OF_PROCESSORS}")
message("ProcessorCount: using environment variable")
elseif(APPLE)
# Mac:
find_program(ProcessorCount_cmd_sysctl sysctl
PATHS /usr/sbin)
if(ProcessorCount_cmd_sysctl)
execute_process(COMMAND ${ProcessorCount_cmd_sysctl} -n hw.ncpu
OUTPUT_STRIP_TRAILING_WHITESPACE
OUTPUT_VARIABLE count)
message("ProcessorCount: using sysctl '${ProcessorCount_cmd_sysctl}'")
endif()
else()
# Linux (systems with getconf):
find_program(ProcessorCount_cmd_getconf getconf)
if(ProcessorCount_cmd_getconf)
execute_process(COMMAND ${ProcessorCount_cmd_getconf} _NPROCESSORS_ONLN
OUTPUT_STRIP_TRAILING_WHITESPACE
OUTPUT_VARIABLE count)
message("ProcessorCount: using getconf '${ProcessorCount_cmd_getconf}'")
endif()
if(NOT count)
# QNX (systems with pidin):
find_program(ProcessorCount_cmd_pidin pidin)
if(ProcessorCount_cmd_pidin)
execute_process(COMMAND ${ProcessorCount_cmd_pidin} info
OUTPUT_STRIP_TRAILING_WHITESPACE
OUTPUT_VARIABLE pidin_output)
string(REGEX MATCHALL "Processor[0-9]+: " procs "${pidin_output}")
list(LENGTH procs count)
message("ProcessorCount: using pidin '${ProcessorCount_cmd_pidin}'")
endif()
endif()
endif()
# Execute this code when there is no 'sysctl' or 'getconf' or 'pidin' or
# when previously executed methods return empty output:
#
if(NOT count)
# Systems with /proc/cpuinfo:
set(cpuinfo_file /proc/cpuinfo)
if(EXISTS "${cpuinfo_file}")
file(STRINGS "${cpuinfo_file}" procs REGEX "^processor.: [0-9]+$")
list(LENGTH procs count)
message("ProcessorCount: using cpuinfo '${cpuinfo_file}'")
endif()
endif()
# Ensure an integer return (avoid inadvertently returning an empty string
# or an error string)... If it's not a decimal integer, return 0:
#
if(NOT count MATCHES "^[0-9]+$")
set(count 0)
endif()
set(${var} ${count} PARENT_SCOPE)
endfunction()
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