Finds prime numbers from 1 to whatever you choose. Has a built in time to see how long it took to find all hte primes.
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//**************************************
// Name: A Prime Number Finder
// Description:Finds prime numbers from 1 to whatever you choose. Has a built in time to see how long it took to find all hte primes.
// By: Robert Peterson
//
//This code is copyrighted and has// limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=1261&lngWId=8//for details.//**************************************
<?
$time_start = microtime(1);
$x = 250; // From 1 to x
for($i=1;$i<=$x;$i++) {
$f=sqrt($i);
for($z=1;$z<=$f;$z++) {
$y=$i%$z;
if($y==0)
$l++;
if($l>=2)
break;
}
if ($l<=1){
echo "$i, ";
$b++;
}
$l=0;
}
$time_end = microtime(1);
$time = $time_end - $time_start;
echo "<br><b>[Found first $x prime numbers in $time seconds]</b>";
?>
A useful addition would be to allow the user to start from a particular number as well (say from 10,000 to 20,000).
Another addition would be set_time_limit(300). As when I looked for Primes from 1 to 1,000,000 it timed out at 30 seconds (default). 300 seconds, or 5 minutes, should be long enough. (If this comment was disrespectful, please report it.)
wouldnt it be much more efficient if you make it loop over the prime numbers that were already outputted to see if it is prime? (ex, to see if 11 is prime check out all numbers outputed upto sqrt(11)) (If this comment was disrespectful, please report it.)
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2/6/2004 9:22:28 AM: 
