How Can I Accurately Measure the Execution Time of a C Function?

Measuring Execution Time of a Function in C

In C , accurately measuring the execution time of a function can be challenging due to system load variations. This can lead to unreliable results when using standard methods like std::chrono::system_clock::now().

Alternative Approach Using Boost.Chrono

The Boost.Chrono library provides a more precise method for measuring function execution time. Specifically, the process_user_cpu_clock function captures the CPU time spent by the current process.

Using process_user_cpu_clock

To use process_user_cpu_clock, include the chrono header and follow these steps:

1. Define a function to time:

void timed_function() {
    // Your code to execute
}

2. Measure the execution time:

using namespace boost::chrono;
duration<double, std::milli> elapsed;
auto start = process_user_cpu_clock();
timed_function();
auto end = process_user_cpu_clock();
elapsed = end - start;

The variable elapsed will contain the duration of the timed function in milliseconds.

High-Resolution Clock in C 11

If using C 11 or later, you can also utilize the std::chrono::high_resolution_clock for precise timing. The usage is similar to Boost.Chrono, as demonstrated in the following example:

using namespace std::chrono;
using ms = milliseconds;
auto t1 = high_resolution_clock::now();
timed_function();
auto t2 = high_resolution_clock::now();
duration<ms> elapsed = t2 - t1;

Speed Comparison

By using either Boost.Chrono or std::chrono::high_resolution_clock, you can accurately measure and compare the execution times of functions to determine their relative speeds.

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