Java C++ help, im comparing the execution times of both languages but c++ took a lot of time w/ for loop.HELP?

Question

I am comparing C++ and java, java using eclipse, c++ using bloodshed dev C++
Java took about 16 seconds to run the for loop, but c++ took over an hour.
i was wondering if i did something wrong, or if i should switch the compiler, if so please reccomend a good free one.
My java code is as follows:
//import java.util.*;
public class Time
{
public Time(){}
public static void main(String args[])
{
long startTime = System.currentTimeMillis();
Time ext=new Time();
ext.callMethod();
long endTime = System.currentTimeMillis();
System.out.println("Total elapsed time in execution of method callMethod() is :"+ (endTime-startTime));
}
public void callMethod(){
System.out.println("Calling method");

for(int i=1;i<=1000000;i++)
{

System.out.println("Value of counter is "+i);
}

if you have suggestion for the code please comment.
for c++:
#include
#include
#include
using namespace std;
int main()
{
clock_t start, end;

start = clock();
int i;
for(i=0; i<1000000+1; i+=1){
system("Cls");
cout<< i << endl;}

end = clock();

cout << "Time required for execution: "
<< (double)(end-start)/CLOCKS_PER_SEC
<< " seconds." << "\n\n";
Sleep(10000);
return 0;

}
please give suggestions. Thank You!!!

Answer 1

I suspect the problem with the C++ version is here:



system("Cls");



System calls are extremely expensive. The computer has to do a whole lot more stuff when you make a system call. To put into perspective, when Java calls System.out.println(), it's like writing a message on a slip of paper and handing it to your friend sitting next to you, and when C++ calls system("Cls"), it's like carving a message onto a giant block of marble and shipping it by air to your friend in South Africa. The latter just takes way more time and resources.



In any case, printing itself is already a relatively large resource hog. I suspect that if you remove all the commands from inside both for loops, and just measure the time it takes the processor to spin that much, you'll find that both cases will run much faster (probably in less than 10 milliseconds, although it depends on your system).

Answer 2

Why are your for loops so different?



In the Java you use:

for(int i=1;i<=1000000;i++)





and in the C++ you use:

for(i=0; i<1000000+1; i+=1){



The C++ has more operations involved.

Furthermore, why are you calling

system("Cls");

in your C++ loop? This adds more time! How much? I don't know but it's certainly not zero.



It also depends on how you executed the codes. If you did them within the IDEs then there's significant overhead. To compare the execution of 2 codes you should execute the class file for Java and the exe file for C++.



You have a great future in advertising. Those are very different codes and yet you want to compare results. You comparison is deeply flawed.

Answer 3

Replace



     system("Cls");

     cout<< i << endl;



with



     cout << "Value of counter is " << i << '\n';



to make it a fair comparison. (and no, "i<=1000000;i++" and "i<1000000+1; i+=1" are identical from compiler's point of view, that is not the source of any difference)



EDIT: apparently System.out.println() flushes the output buffer every time, so endl is in fact more appropriate than '\n'. But, in any case, what you're comparing is the speed of the screen output subsystem, which is hardly a representative comparison of the languages (most of the time is spent in the OS, not in your program)



On my home computer, your Java program executes in 1.40 seconds, and your C++ program with loop body " cout << "Value of counter is " << i << endl;" executes in 0.23 seconds (replacing endl with '\n' drops execution time to 0.18 seconds)

Answer 4

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Answer 5

im not that much into c++ but i think the time consuming thing is system("Cls"); because it always runs a system command, which honestly is very time consuming. In java code you use system.out, which also is time consuming but not that much. try cout << "cls" << endl; and it might be much faster..

Answer 6

In addition to what's been said already, using i+=1 instead of i++ for the C++ version may be slowing it down (I don't know how good the compiler for dev C++ is at optimizing).

Answer 7

Where is your clock() function at?

Plus what are these.../* clock_t start, end;*/

functions maybe? if so need to be like this...

int clock_t(int Start,int end)

{

//Code here

return end;

}