Primes

primes.php

<?php

function seive($candidates, $min = 0, $max = 0) {
	$primes = array();
	$last = ($max == 0) ? floor(end($candidates) / 2) : $max;
	$i = ($min == 0) ? reset($candidates) : $min;
	while($i <= $last) {
		
		$candidates = array_filter($candidates, function($n) use ($i, &$primes)  {
			if($n < $i) {
				$primes[] = $n;
				return false;
			}
			$e = $n / $i;
			if($e == 1) return true;
			if($e != floor($e)) return true;
			return false;
		});
		$i++;
	}
	$primes = array_merge($primes, $candidates);
	return $primes;
}

function calculatePrime() {

	// Generate big wheel
	$init = 300;
	$candidates = range(2, $init);
	$primes = seive($candidates, 2, $init);
	$min = max($primes);

	for($z = 1; $z <= 5; $z++) {
		// Multiply out big wheel
		$candidates = $primes;
		foreach($primes as $prime) {
			$candidates[] = $prime + $init * $z;
		}

		// Re-seive
//		echo " * Seive pass $z, " . count($candidates) . " candidates, " . count($primes) . " primes\n";
		$primes = seive($candidates, $min);
	}

	return $primes;
}


$res = calculatePrime();
echo implode("\n", $res);
//echo "\n * " . count($res) . "\n";

?>