[Issue 2977] New: std.random.unpredictableSeed() should use thread ID somewhere

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=2977

           Summary: std.random.unpredictableSeed() should use thread ID
                    somewhere
           Product: D
           Version: 2.030
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: dsimcha at yahoo.com


uint unpredictableSeed()
{
    static bool seeded;
    static MinstdRand0 rand;
    if (!seeded) {
        rand.seed(getpid ^ cast(uint)getUTCtime);
        seeded = true;
    }
    rand.popFront;
    return cast(uint) (getUTCtime ^ rand.front);
}

If called from multiple threads at exactly the same time, unpredictableSeed
gives every thread the same seed.  This is annoying when running the same monte
carlo simulation simultaneously in multiple threads, since I tend to spawn all
of the threads at exactly the same time.  Something like:

(getpid + cast(uint) Thread.getThis) ^ cast(uint) getUTCtime

might work well.

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