function N = num_cores()
%NUM_CORES attempt to find the number of cores/CPUs on the current machine

% Iain Murray, March 2011

N = [];

try
    % Undocumented Matlab routine.
    % Could disappear and not currently (2011-03-06) in Octave:
    N = feature('numCores');
catch
    try
        if exist('/proc/cpuinfo', 'file')
            % Should work on Linux in Matlab and Octave:
            fid = fopen('/proc/cpuinfo');
            N = length(strfind(char(fread(fid)'), ['processor' 9]));
            fclose(fid);
        elseif ispc
            % Windows is untested
            N = str2num(getenv('NUMBER_OF_PROCESSORS'));
        elseif ismac
            % Mac is untested
            [status, output] = system('sysctl hw.ncpu | awk ''{print $2}''');
            N = str2num(output);
        end
    end
end

if isempty(N)
    warning('Was not able to find number of cores. Falling back to 1.');
    N = 1;
end