Method: Autobuild.autodetect_processor_count

Defined in:
lib/autobuild/subprocess.rb

.autodetect_processor_count ⇒ Object

Returns the number of CPUs present on this system



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# File 'lib/autobuild/subprocess.rb', line 77

def self.autodetect_processor_count
    return @processor_count if @processor_count

    if File.file?('/proc/cpuinfo')
        cpuinfo = File.readlines('/proc/cpuinfo')
        physical_ids  = []
        core_count    = []
        processor_ids = []
        cpuinfo.each do |line|
            case line
            when /^processor\s+:\s+(\d+)$/
                processor_ids << Integer($1)
            when /^physical id\s+:\s+(\d+)$/
                physical_ids << Integer($1)
            when /^cpu cores\s+:\s+(\d+)$/
                core_count << Integer($1)
            end
        end

        # Try to count the number of physical cores, not the number of
        # logical ones. If the info is not available, fallback to the
        # logical count
        has_consistent_info =
            (physical_ids.size == core_count.size) &&
            (physical_ids.size == processor_ids.size)
        if has_consistent_info
            info = Array.new
            while (id = physical_ids.shift)
                info[id] = core_count.shift
            end
            @processor_count = info.compact.inject(&:+)
        else
            @processor_count = processor_ids.size
        end
    else
        result = Open3.popen3("sysctl", "-n", "hw.ncpu") do |_, io, _|
            io.read
        end
        @processor_count = Integer(result.chomp.strip) unless result.empty?
    end

    # The format of the cpuinfo file is ... let's say not very standardized.
    # If the cpuinfo detection fails, inform the user and set it to 1
    unless @processor_count
        # Hug... What kind of system is it ?
        Autobuild.message "INFO: cannot autodetect the number of CPUs on this sytem"
        Autobuild.message "INFO: turning parallel builds off"
        Autobuild.message "INFO: you can manually set the number of parallel build "\
            "processes to N"
        Autobuild.message "INFO: (and therefore turn this message off)"
        Autobuild.message "INFO: with"
        Autobuild.message "    Autobuild.parallel_build_level = N"
        @processor_count = 1
    end

    @processor_count
end