Java is 1000 times faster than c++ on my computer???
Ok, this is driving me batty. I recently had an assignment to implement Floyds algorithm and Dijkstras on a graph with 5403 vertices. (in java) my program was running impossibly slow so I started troubleshooting. As part of that troubleshooting I wrote a 3 level nested for loop in Java, and the same set of loops in C++. The Java version is running 1000 times faster than the C++ version. I just KNOW Java is not 1000 times faster than C++ Can anybody suggest what might be going on here? Here's the code
Code:
In C++:
#include <iostream>
#include <ctime>
using namespace std;
int main(int argc, char *argv[])
{
unsigned start = time(0);
cout << "start is " << start << endl;
int count=0;
for (int i=0;i<5404;i++)
{
cout << "i = " << i << endl;
for (int j=0;j<5404;j++)
{
for (int k=0;k<5404;k++)
{
count ++;
}
}
}
unsigned finish = time(0);
unsigned total = finish-start;
cout << "n^3 took: "<< total << "seconds" << endl;
return 0;
}// end main
Output:
.
.
.
i = 5400
i = 5401
i = 5402
i = 5403
finish is 1243916727
n^3 took: 323seconds
Java:
public class Main
{
public static void main(String[] args)
{
int count=0;
long start = System.currentTimeMillis();
for(int k=0;k<5404;k++)
{
System.out.println( "k= " + k);
for (int i=0;i<5404;i++)
{
for(int j=0;j<5404;j++)
{
count++;
}
}
}
long finish=System.currentTimeMillis();
long totalTime=(finish-start);
System.out.println("n^3 took " + totalTime / 1000.0 + " seconds");
}
} // end main
Output:
.
.
.
k= 5400
k= 5401
k= 5402
k= 5403
n^3 took 0.332 seconds
Just to flesh out the details. My computer is an amd dual core 2.7Ghz with 4Gb Ram running Ubuntu 9.10.
Java is
java version "1.6.0_0"
OpenJDK Runtime Environment (IcedTea6 1.4.1) (6b14-1.4.1-0ubuntu7)
OpenJDK 64-Bit Server VM (build 14.0-b08, mixed mode)
C compiler is:
g++ (Ubuntu 4.3.3-5ubuntu4) 4.3.3
Copyright (C) 2008 Free Software Foundation, Inc.
commands
java Main
g++ main.cpp
