numberfact.cpp

#include <stdlib.h>
#include <stdio.h>
#include <math.h> 
#include <ctime>

#define N_MAX 100000000

int main() {

	int n = 4;
	double f = 1.0;
	long k = 1;
	
	long startTime = clock();
	
	for(; k < N_MAX; k++) {
		f *= pow(1.0 + (1.0 / k), n) / (1.0 + ((double) n / k));
	}
	
	long stopTime = clock();
	
	printf("%d! = %f in %d ms (%d iterations)\n", n, f, stopTime - startTime, k);
	return 0;
}

NumberFact.java

public class NumberFact {

    public static void main(String[] args) {

        int n = 4;
        double f = 1.0;
        long k = 1;
        
        long startTime = System.currentTimeMillis();
        
        for (; k < 100_000_000; k++) {
            f *= Math.pow(1.0 + (1.0 / k), n) / (1.0 + ((double) n / k));
        }

        long endTime = System.currentTimeMillis();

        System.out.println(n + "! = " + f + " in " + (endTime - startTime) + " ms (" + k + " iterations)");
    }
}

NumberFact.php

<?php

$n = 4.0;
$f = 1.0;
$k = 1;

$startTime = round(microtime(true) * 1000);

for (; $k < 100000000; $k++) {
    $f *= pow(1.0 + (1.0 / $k), $n) / (1.0 + ($n / $k));
}

$endTime = round(microtime(true) * 1000);

echo $n . "! = " . $f . " in " . ($endTime - $startTime) . " ms (" . $k . " iterations)\n";
		
?>

Results

Java:	4! = 23.999998473795994 in 12827 ms (100000000 iterations)
C++:	4! = 23.999999 in 23280 ms (100000000 iterations)
PHP:	4! = 23.999998473786 in 23602 ms (100000000 iterations)