Re: gthread: how many cores do I have?

[Ryan Lortie <desrt desrt ca>]

On Mon, 2010-03-15 at 23:43 +0100, Sven Neumann wrote:
> Feel free to use the implementation in GIMP as a starting point:
> 
>  http://git.gnome.org/browse/gimp/tree/app/base/base-utils.c#n54

See also:

http://qt.gitorious.org/qt/qt/blobs/4.7/src/corelib/thread/qthread_unix.cpp
http://qt.gitorious.org/qt/qt/blobs/4.7/src/corelib/thread/qthread_win.cpp


the QThread::idealThreadCount() function.

On Windows, that's:

    SYSTEM_INFO sysinfo;
    GetSystemInfo(&sysinfo);
    return sysinfo.dwNumberOfProcessors;

MacOS X:
    MPProcessorsScheduled();

HPUX:
    struct pst_dynamic psd;

    if (pstat_getdynamic(&psd, sizeof(psd), 1, 0) == -1) {
        perror("pstat_getdynamic");
        cores = -1;
    } else {
        cores = (int)psd.psd_proc_cnt;
    }

{Free,Net,Open}BSD:
    size_t len = sizeof(cores);
    int mib[2];
    mib[0] = CTL_HW;
    mib[1] = HW_NCPU;
    if (sysctl(mib, 2, &cores, &len, NULL, 0) != 0) {
        perror("sysctl");
        cores = -1;
    }

"integrity" OS, symbian: hard-coded to one core.

VXWorks: a loop to check if CPU #n exists until it fails (see link)

IRIX:
    cores = (int)sysconf(_SC_NPROC_ONLN);

all other Unix (including Linux):
    cores = (int)sysconf(_SC_NPROCESSORS_ONLN);


Cheers