C some Speed !!

Most programmers know that c programs are the next best thing to assembly language programs in terms of Speed , and here is yet another example .

When solving one of the problems at projecteuler.net.I Suddenly came upon the idea to compare the speed of execution of the same algorithm in different languages.

So here is the program in Three Programming languages , C , Java and Python

First in C

#include<stdio.h>
long long  LargestPrimeFactor(long long number) {
		long long n = number , i , Largestfactor = 1;
		for (i = 2; i <= (n / i); i++) {
			while (n % i == 0) {
				Largestfactor = i > Largestfactor? i : Largestfactor;
				n /= i;
			}
		}
		Largestfactor = n > Largestfactor ? n : Largestfactor;

		return Largestfactor;
	}
int main (){
	printf(" %d \n",LargestPrimeFactor(600851475143));
}

Then in Java

class ex3{
	public static long LargestPrimeFactor(long number) {
		long n = number, factor = 1 , i;
		for (i = 2; i <= n / i; i++) {
			while (n % i == 0) {
				factor = i>factor?i:factor;
				n /= i;
			}
		}
		factor = n>factor?n:factor;
		return factor;
	}
	public static void main(String [] args){
		System.out.println(LargestPrimeFactor(600851475143L));
	}
}

and now in Python

def LargestPrimeFactor(num):
        n=num
        factor = 1
        i=2
        while( i<= (n/i) ):
                while( n%i == 0 ):
                        if i>factor :
                                factor = i
                        n /= i
                i += 1
        if n > factor:
                factor = n
        return factor

print LargestPrimeFactor(600851475143)

I computed the times using the time utility in linux .

I expected the c program to win there was no doubt about that , and java was expected to come in second with python last .

$ time ./a.out
 6857

real	0m0.003s
user	0m0.004s
sys	0m0.000s

$ time java ex3
6857

real	0m0.114s
user	0m0.084s
sys	0m0.028s

$ time python ex3.py
6857

real	0m0.035s
user	0m0.028s
sys	0m0.004s

From the results its quite visible that c had won over python and python had won over java ,even though java was supposed to be faster than python.

The reason for python winning is that the cost of starting up the JVM is quite high, when compared with the cost of starting the python interpreter.

So lesson learnt If your program is short run it in python when given a choice , but still C is the king of Speed

Ps: This Question on stackoveflow goes over some more details .