How Can I Accurately Measure Elapsed Time in C ?

Easily Measure Elapsed Time

To accurately measure the elapsed time of program segments, alternatives are available to the less precise time() function.

Using gettimeofday()

As shown in the provided code, gettimeofday() offers timer precision down to microseconds. By calculating the difference between a start and end time measurement, you can obtain elapsed time values.

Interpreting Results

Time value interpretation:

• time taken = 0 26339: Represents 26,339 microseconds, or approximately 26.339 milliseconds.
• time taken = 4 45025: Represents 4 seconds and 45.025 milliseconds.

C 11 Approach

A more modern and precise approach uses the C 11 library:

• std::chrono::steady_clock::now(): Retrieves the current time with nanosecond precision.
• duration_cast: Converts the time difference to the desired unit (e.g., microseconds or nanoseconds).

Example Code

// C++11 Style:
#include <chrono>

std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();

std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::microseconds>(end - begin).count() << "[µs]" << std::endl;
std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin).count() << "[ns]" << std::endl;

This code calculates the time difference in both microseconds and nanoseconds, offering more precise measurements than time() or gettimeofday().

The above is the detailed content of How Can I Accurately Measure Elapsed Time in C ?. For more information, please follow other related articles on the PHP Chinese website!