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I was playing around with some FizzBuzz code in Java when i wanted to compare it to C++.

I ran the Code below in Java and essentially the same Code in C++.

Java Eclipse IDE runtime: 11sec

C++ Code Blocks IDE runtime: 202sec (about 18 times slower than Java)

C++ Visual Studio IDE runtime: 281sec (about 25 times slower than Java)

I have the newest version installed of all of these IDEs as far as i know.

Why is this happening? Every information i have says that C++ should run faster.

Java Code:

public class Test { public static void main(String []args) { double fizzes = 0; double buzzes = 0; double fizzbuzzes = 0; double normals = 0; double iterations = 1000000; for (int x = 0; x < iterations; x++) { int index = 0; String output = ""; if (x % 3 == 0) { output = output + "Fizz"; index = 1; } if (x % 5 == 0) { output = output + "Buzz"; index = index + 2; } if (output == "") { //x%5!=0 && x%3!=0 System.out.println(x); normals++; } else { System.out.println(output); } if (index == 3) { fizzbuzzes++; } else if (index == 2) { buzzes++; } else if (index == 1) { fizzes++; } } System.out.println("Normals " + (normals/iterations*100) + "%"); //percent System.out.println("Fizzes " + (fizzes/iterations*100)+ "%"); System.out.println("Buzzes " + (buzzes/iterations*100)+ "%"); System.out.println("FizzBuzzes " +(fizzbuzzes/iterations*100)+ "%"); } }

C++ Code:

#include "stdafx.h" #include "iostream" using namespace std; int main() { double fizzes = 0; double buzzes = 0; double fizzbuzzes = 0; double normals = 0; double iterations = 1000000; for (int x = 0; x < iterations; x++) { int index = 0; string output = ""; if (x % 3 == 0) { output = output + "Fizz"; index = 1; } if (x % 5 == 0) { output = output + "Buzz"; index = index + 2; } if (output == "") { //x%5!=0 && x%3!=0 cout << x<< endl; normals++; } else { cout << (output)<< endl; } if (index == 3) { fizzbuzzes++; } else if (index == 2) { buzzes++; } else if (index == 1) { fizzes++; } } cout << "Normals " << (normals / iterations * 100) <<"%"<< endl; //percentage cout << "Fizzes " << (fizzes / iterations * 100) << "%" << endl; cout << "Buzzes " << (buzzes / iterations * 100) << "%" << endl; cout << "FizzBuzzes " << (fizzbuzzes / iterations * 100) << "%" << endl; return 0; }

This just gives the count of Fizz/Buzzes in percentage.

Is this just a result of my IDE configurations?

EDIT: changed the C++ code to your suggestions

#include "stdafx.h" #include <iostream> #include <string> int main() { double fizzes = 0; double buzzes = 0; double fizzbuzzes = 0; double normals = 0; double iterations = 1000000; for (int x = 0; x < iterations; x++) { int index = 0; std::string output = ""; if (x % 3 == 0) { output = output + "Fizz"; index = 1; } if (x % 5 == 0) { output = output + "Buzz"; index = index + 2; } if (index == 3) { fizzbuzzes++; } else if (index == 2) { buzzes++; } else if (index == 1) { fizzes++; } if (output == "") { //x%5!=0 && x%3!=0 //std::cout << x << "\n"; normals++; } //else { // std::cout << output << "\n"; //} } std::cout << "Normals " << (normals / iterations * 100) <<"%"<< "\n"; //percentage std::cout << "Fizzes " << (fizzes / iterations * 100) << "%" << "\n"; std::cout << "Buzzes " << (buzzes / iterations * 100) << "%" << "\n"; std::cout << "FizzBuzzes " << (fizzbuzzes / iterations * 100) << "%" << "\n"; int z; std::cin >> z; //so i can see the values return 0; }

Also build in Release mode and outside of the IDE it runs pretty much instantly. Seems like printing takes alot of time.

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    How did you compile your C++? Did you use any optimization flags? It's pointless to discuss speed if your compiler is avoiding most optimizations and emitting stuff for debugging purposes. Commented Mar 4, 2018 at 14:30
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    Pehaps you did not build you program in Release mode, or otherwise built it without any optimization. You should also try to run your code outside your IDE - you program produces a lot of text output, and some IDEs can take a whole lot of time displaying all that output, instead of letting your program run as fast as it can. (Your C++ program takes 5 seconds to complete on my machine..) Commented Mar 4, 2018 at 14:33
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    The first step: turn that off: sync_with_stdio Commented Mar 4, 2018 at 14:34
  • 5
    And instead of endl use '\n' Commented Mar 4, 2018 at 14:35
  • 2
    std::endl is evil Commented Mar 4, 2018 at 14:39

1 Answer 1

Reset to default
7

This is quite interesting, I test this in my PC, it is the same result.

Then I try to disable the print in both java and c++ (release with -O3), the time usage is <3 seconds for both.

So the problem is cout flush every time, but java is running inside a IDE, the IDE will buffer all the output,so this should be the reason why java is faster than c++.

Then I try to run java with console, and it take much longer than running inside IDE.

This should be align with the test of redirect the c++ ouputput to /dev/null by https://stackoverflow.com/users/3807729/galik

Then I change the java code to a buffered writer, the time reduced to 5 seconds inside IDE.

import java.io.BufferedWriter; import java.io.FileOutputStream; import java.io.OutputStreamWriter; public class Test { public static void main(String []args) throws Exception{ double fizzes = 0; double buzzes = 0; double fizzbuzzes = 0; double normals = 0; double iterations = 1000000; BufferedWriter sout = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(java.io.FileDescriptor.out),"ASCII"), 1024); for (int x = 0; x < iterations; x++) { int index = 0; StringBuilder output = new StringBuilder(); if (x % 3 == 0) { output.append("Fizz"); index = 1; } if (x % 5 == 0) { output.append("Buzz"); index = index + 2; } if (output.length()==0) { //x%5!=0 && x%3!=0 sout.write(String.valueOf(x)); sout.write("\r\n"); normals++; } else { sout.write(output.toString()); sout.write("\r\n"); } if (index == 3) { fizzbuzzes++; } else if (index == 2) { buzzes++; } else if (index == 1) { fizzes++; } } System.out.println("Normals " + (normals/iterations*100) + "%"); //percent System.out.println("Fizzes " + (fizzes/iterations*100)+ "%"); System.out.println("Buzzes " + (buzzes/iterations*100)+ "%"); System.out.println("FizzBuzzes " +(fizzbuzzes/iterations*100)+ "%"); } }
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