Prime Factorizing For Big Evil Number '$bignumber'";
for ($i = 2; $i < $bignumber-1; $i++) {
//print "
$i";
if (isprime($i)) { // if $i is a prime
//print " Prime ";
if (isprimefactor($bignumber, $i)) { // $i is a prime, now test if it's a primefactor
//print " Factor!";
$foundfactors[] = $i;
if (testfactor($bignumber, $foundfactors)) {
print "
Breaking because testfactor() is happy.";
break;
}
}
}
}
print "
All done, prime factors collected are:";
print_r($foundfactors);
print "
Largest Factor: " . end($foundfactors);
print "
Total Memory Used: " . memory_get_peak_usage(TRUE)/1024 . " Kbytes";
// =======================================================
// everything in math can be undone, and factors can be divided backwards
// so lets test, so we can exit the factorization loop midstream
function testfactor($bigevilnumber, $factors) {
// set point to last item in array, and do bignum / last factor
end($factors);
$y = $bigevilnumber / current($factors);
while(prev($factors)) {
$z = $y / current($factors);
$y = $z;
}
reset($factors);
if ($y==1) return TRUE;
else return FALSE;
}
function isprime($num) {
if ($num==1) return false; // 1 is not a prime
if ($num<4) return true; // 2 and 3 are primes
if (($num%2)==0) return false; // exclude evens, all primes are odd
if ($num<9) return true; // 4,6,8 already excluded
if (($num%3)==0) return false; // exclude remaining multiples of 3
$primefound = FALSE;
// test num from 2 up to sqrt(num)
for ($m=2; $m<=sqrt($num); $m++) {
if (($num % $m)==0) { // composite, quit now
return false;
} else {
$primefound = TRUE;
}
}
return ($primefound);
}
function isprimefactor($bignumber, $primenumber) {
if (($bignumber % $primenumber)==0) {
return TRUE;
}
return FALSE;
}
?>