cmake/Modules/ProcessorCount.cmake

# - ProcessorCount(var)
# Determine the number of processors/cores and save value in ${var}
#
# Sets the variable named ${var} to the number of physical cores available on
# the machine if the information can be determined. Otherwise it is set to 0.
# Currently this functionality is implemented for AIX, cygwin, FreeBSD, HPUX,
# IRIX, Linux, Mac OS X, QNX, Sun and Windows.
#
# This function is guaranteed to return a positive integer (>=1) if it
# succeeds. It returns 0 if there's a problem determining the processor count.
#
# Example use, in a ctest -S dashboard script:
#
#   include(ProcessorCount)
#   ProcessorCount(N)
#   if(NOT N EQUAL 0)
#     set(CTEST_BUILD_FLAGS -j${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.

# 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 2010-2011 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: WIN32, trying environment variable")
  endif()

  if(NOT count)
    # Mac, FreeBSD, OpenBSD (systems with sysctl):
    find_program(ProcessorCount_cmd_sysctl sysctl
      PATHS /usr/sbin /sbin)
    if(ProcessorCount_cmd_sysctl)
      execute_process(COMMAND ${ProcessorCount_cmd_sysctl} -n hw.ncpu
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE count)
      #message("ProcessorCount: trying sysctl '${ProcessorCount_cmd_sysctl}'")
    endif()
  endif()

  if(NOT count)
    # Linux (systems with getconf):
    find_program(ProcessorCount_cmd_getconf getconf)
    if(ProcessorCount_cmd_getconf)
      execute_process(COMMAND ${ProcessorCount_cmd_getconf} _NPROCESSORS_ONLN
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE count)
      #message("ProcessorCount: trying getconf '${ProcessorCount_cmd_getconf}'")
    endif()
  endif()

  if(NOT count)
    # HPUX (systems with machinfo):
    find_program(ProcessorCount_cmd_machinfo machinfo
      PATHS /usr/contrib/bin)
    if(ProcessorCount_cmd_machinfo)
      execute_process(COMMAND ${ProcessorCount_cmd_machinfo}
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE machinfo_output)
      string(REGEX MATCHALL "Number of CPUs = ([0-9]+)" procs "${machinfo_output}")
      set(count "${CMAKE_MATCH_1}")
      #message("ProcessorCount: trying machinfo '${ProcessorCount_cmd_machinfo}'")
    endif()
  endif()

  if(NOT count)
    # IRIX (systems with hinv):
    find_program(ProcessorCount_cmd_hinv hinv
      PATHS /sbin)
    if(ProcessorCount_cmd_hinv)
      execute_process(COMMAND ${ProcessorCount_cmd_hinv}
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE hinv_output)
      string(REGEX MATCHALL "([0-9]+) .* Processors" procs "${hinv_output}")
      set(count "${CMAKE_MATCH_1}")
      #message("ProcessorCount: trying hinv '${ProcessorCount_cmd_hinv}'")
    endif()
  endif()

  if(NOT count)
    # AIX (systems with lsconf):
    find_program(ProcessorCount_cmd_lsconf lsconf
      PATHS /usr/sbin)
    if(ProcessorCount_cmd_lsconf)
      execute_process(COMMAND ${ProcessorCount_cmd_lsconf}
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE lsconf_output)
      string(REGEX MATCHALL "Number Of Processors: ([0-9]+)" procs "${lsconf_output}")
      set(count "${CMAKE_MATCH_1}")
      #message("ProcessorCount: trying lsconf '${ProcessorCount_cmd_lsconf}'")
    endif()
  endif()

  if(NOT count)
    # QNX (systems with pidin):
    find_program(ProcessorCount_cmd_pidin pidin)
    if(ProcessorCount_cmd_pidin)
      execute_process(COMMAND ${ProcessorCount_cmd_pidin} info
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE pidin_output)
      string(REGEX MATCHALL "Processor[0-9]+: " procs "${pidin_output}")
      list(LENGTH procs count)
      #message("ProcessorCount: trying pidin '${ProcessorCount_cmd_pidin}'")
    endif()
  endif()

  if(NOT count)
    # Sun (systems where uname -X emits "NumCPU" in its output):
    find_program(ProcessorCount_cmd_uname uname)
    if(ProcessorCount_cmd_uname)
      execute_process(COMMAND ${ProcessorCount_cmd_uname} -X
        ERROR_QUIET
        OUTPUT_STRIP_TRAILING_WHITESPACE
        OUTPUT_VARIABLE uname_X_output)
      string(REGEX MATCHALL "NumCPU = ([0-9]+)" procs "${uname_X_output}")
      set(count "${CMAKE_MATCH_1}")
      #message("ProcessorCount: trying uname -X '${ProcessorCount_cmd_uname}'")
    endif()
  endif()

  # Execute this code when all previously attempted 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]+$")
      list(LENGTH procs count)
      #message("ProcessorCount: trying cpuinfo '${cpuinfo_file}'")
    endif()
  endif()

  # Since cygwin builds of CMake do not define WIN32 anymore, but they still
  # run on Windows, and will still have this env var defined:
  #
  if(NOT count)
    set(count "$ENV{NUMBER_OF_PROCESSORS}")
    #message("ProcessorCount: last fallback, trying environment variable")
  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()