srand(time(NULL)) generating similar results [duplicate]

Answer 1

From @James Kanze's test it seems that it is a peculiarity of VC++'s C runtime (though I am certain other libraries suffer in the same way). This library also suffers from having a minimum allowable RAND_MAX, but that's another issue.

The solution to the low variance of the initial value is simply to discard it:

void seed_rand( unsigned int seed )
{
    srand( seed ) ;
    (void)rand() ;
}

int main()
{
    seed_rand( time( NULL ) );
    int r1 = rand();
    std::cout << r1 << ' ' << rand() << std::endl;
    return 0;
}