Comments on: Sieve of Eratosthenes in PhP http://www.think-lamp.com/2008/08/sieve-of-eratosthenes-in-php/ Everything Linux Apache Php Mysql Wed, 13 Apr 2011 07:34:29 +0000 hourly 1 http://wordpress.org/?v=3.1.1 By: admin http://www.think-lamp.com/2008/08/sieve-of-eratosthenes-in-php/comment-page-1/#comment-6603 admin Mon, 16 Aug 2010 02:16:33 +0000 http://www.think-lamp.com/?p=37#comment-6603 [php] <?php echo "test"; ?> [/php] <?php echo "test"; ?> ]]> By: Ali http://www.think-lamp.com/2008/08/sieve-of-eratosthenes-in-php/comment-page-1/#comment-6476 Ali Sun, 08 Aug 2010 21:44:59 +0000 http://www.think-lamp.com/?p=37#comment-6476 Comment system isn't great >.< Ignore the last $total+3x } Comment system isn’t great >.<

Ignore the last $total+3x }

]]> By: Ali http://www.think-lamp.com/2008/08/sieve-of-eratosthenes-in-php/comment-page-1/#comment-6475 Ali Sun, 08 Aug 2010 21:44:12 +0000 http://www.think-lamp.com/?p=37#comment-6475 I gave this a go, finds all primes < 1million in ~0.44s function CountPrimes($max) { $vals = Array(); $total = 1; for($i=3; $i<$max; $i += 2) { if(!isset($vals[$i])) { $total++; $l = 2*$i; for($j = $i*$i; $j < $max; $j += $l) { $vals[$j] = true; } } } return $total; } } } return $total; } I gave this a go, finds all primes < 1million in ~0.44s

function CountPrimes($max) {
$vals = Array();
$total = 1;
for($i=3; $i<$max; $i += 2) {
if(!isset($vals[$i])) {
$total++;
$l = 2*$i;
for($j = $i*$i; $j < $max; $j += $l) {
$vals[$j] = true;
}
}
}
return $total;
}

}
}
return $total;
}

]]> By: playfish http://www.think-lamp.com/2008/08/sieve-of-eratosthenes-in-php/comment-page-1/#comment-5071 playfish Sun, 21 Mar 2010 04:19:31 +0000 http://www.think-lamp.com/?p=37#comment-5071 i was beginning to feel i may end up being the only woman / man which thought about this, at the very least currently i realize i'm not loco :) i am going to be sure to take a look at some other posts just after i get some caffeine in me, it can be stressful to read with out my coffee, I was up late last night jamming facebook poker and after downing a few ales i ended up giving up all my zynga poker chips take care :) i was beginning to feel i may end up being the only woman / man which thought about this, at the very least currently i realize i’m not loco :) i am going to be sure to take a look at some other posts just after i get some caffeine in me, it can be stressful to read with out my coffee, I was up late last night jamming facebook poker and after downing a few ales i ended up giving up all my zynga poker chips take care :)

]]> By: RiK0 http://www.think-lamp.com/2008/08/sieve-of-eratosthenes-in-php/comment-page-1/#comment-3054 RiK0 Wed, 26 Aug 2009 16:15:57 +0000 http://www.think-lamp.com/?p=37#comment-3054 This is not the Sieve of Eratosthenes. This is a variation on the classical trial division algorithm. That is the reason why this is so slow, it does more computation *and* uses modulo instead of simple addition. This is not the Sieve of Eratosthenes.
This is a variation on the classical trial division algorithm.
That is the reason why this is so slow, it does more computation *and*
uses modulo instead of simple addition.

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