Performance differences between debug and release builds

user_303476 0
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I must admit, that usually I haven't bothered switching between the Debug and Release configurations in my program, and I have usually opted to go for the Debug configuration, even when the programs are actually deployed at the customers place.

As far as I know, the only difference between these configurations if you don't change it manually is that Debug have the DEBUG constant defined, and Release have the Optimize code checked of.

So my questions is actually twofold:

  1. Are there much performance differences between these two configurations. Are there any specific type of code that will cause big differences in performance here, or is it actually not that important?

  2. Are there any type of code that will run fine under the Debug configuration that might fail under Release configuration, or can you be certain that code that is tested and working fine under the Debug configuration will also work fine under Release configuration.

configuration debugging performance .net c#
9 Answers

I know that my answer is VERY late and my answer doesn't exactly what you want but, I thought some solid and simple example to play with would be good. Anyway, this piece of code results in a HUGE difference between Debug and Release. The code is written in C++ on Visual Studio 2019. The code is like this:

#include <iostream>

using namespace std;

unsigned long long fibonacci(int n)
{
    return n < 2 ? n : (fibonacci(n - 1) + fibonacci(n - 2));
}

int main()
{
    int x = 47;

    cout << "Calculating..." << endl;
    cout << "fib(" << x << ") = " << fibonacci(x) << endl;
}

EDIT: Performance Differences in Calculating Fibonacci Sequence

                       Debug        Release         
                C++ x86 C++ x64 C++ x86 C++ x64 C# Debug    C# Release
Time (mSeconds) 99384.9 27799.1 11066.0 11321.5 95233.7 24566.0
Time (Seconds)  99.4    27.8    11.1    11.3    95.2    24.6
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