rand.cs

private static volatile int RandomSeed = 1;

private static int FastRand()
{
retry:
    int oldSeed = RandomSeed;
    int newSeed = unchecked(oldSeed * 1103515245 + 12345);
    if (Interlocked.CompareExchange(ref RandomSeed, newSeed, oldSeed) != oldSeed)
        goto retry;

    int rand = (newSeed >> 16) & 0x7FFF;
    return rand;
}

public static float FloatRand()
{
    int bits = (FastRand() | (FastRand() << 15)) & 0xFFFFFF;
    if (bits == 0) return 0;

    int exp = 127;
    if ((bits & 0xFFF000) == 0) { bits <<= 12; exp -= 12; }
    if ((bits & 0xF30000) == 0) { bits <<=  6; exp -=  6; }
    if ((bits & 0xE00000) == 0) { bits <<=  3; exp -=  3; }
    if ((bits & 0xC00000) == 0) { bits <<=  2; exp -=  2; }
    if ((bits & 0x800000) == 0) { bits <<=  1; exp -=  1; }

    bits |= (exp << 24);

    unsafe
    {
        return *(float *)&bits;
    }
}