I have an array of about 300,000 numbers (0.000000) and want to review each of those numbers to choose those which are within .01 of one another. So, in essence this is 300,000^300,000 values I guess, which takes a while to calculate. I do this simply by loading an array, and then comparing each value in that array with all other values by way of a loop within a loop. The problem is this takes about 10 hours or so to complete, at the least. Can any Monk recommend a coding solution that could speed this up? I tried using PDL but that resulted in no noticeable speed increase. Relevant portions of the code are below... 
for ($n=0;$n<=$#lat;$n++) {

    for ($v=0;$v<=$#lat;$v++) {

    if ($lat[$n] > $lat[$v]-.01 &&
        $lat[$n] < $lat[$v]+.01 &&
    $long[$n] > $long[$v]-.01 &&
    $long[$n] < $long[$v]+.01) {

    if ($numbdate[$n] == ($numbdate[$v]+1) &&
    $timestamp[$n] > 1400 &&
    $timestamp[$v] < 1400) {
            $e++;
            };


    if ($numbdate[$n] == ($numbdate[$v]) &&
    $timestamp[$n] < ($timestamp[$v]-400)) {
            $d++;
            };
    }
}
}

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In reply to fastest way to compare numerical strings? by Anonymous Monk

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