in reply to Random Sampling

Your selection_sample routine is not correctly coded. The idea is to randomly select a sample of n elements as you go, there should not be duplicates in the sample. Change your while loop to the following for a more faithful representation of Knuth's algorithm. 
    while ( @results < $num ) {
        if ( (@$array - $pos) * rand() < $num - @results ) {
            push @results, $array->[$pos];
        }
        $pos++;
    }

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Re: Re: Random Sampling
by demerphq (Chancellor) on Jun 26, 2002 at 17:02 UTC
    Hmm, while you are correct that my code was incorrect, I went with a different fix. My fix was simply to change the line 
    push @results, $array->[$pos];

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    to 
    push @results, $array->[$pos++];

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    But thanks anyway. /me should have tested once or twice more. *sigh*

    Yves / DeMerphq
    ---
    Writing a good benchmark isnt as easy as it might look.

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In Section Cool Uses for Perl