How to Measure Time Taken by a Function to Execute

How to measure time taken by a function to execute

Using performance.now():

var startTime = performance.now()

doSomething()   // <---- measured code goes between startTime and endTime
    
var endTime = performance.now()

console.log(`Call to doSomething took ${endTime - startTime} milliseconds`)

In Node.js it is required to import the performance class

importing performance

const { performance } = require('perf_hooks');

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Using console.time: (living standard)

console.time('doSomething')
    
doSomething()   // <---- The function you're measuring time for 
    
console.timeEnd('doSomething')

Note:
The string being passed to the time() and timeEnd() methods must match
(for the timer to finish as expected).

console.time() documentations:

• MDN documentation
• Node.js documentation

How to measure time taken between lines of code in python?

If you want to measure CPU time, can use time.process_time() for Python 3.3 and above:

import time
start = time.process_time()
# your code here    
print(time.process_time() - start)

First call turns the timer on, and second call tells you how many seconds have elapsed.

There is also a function time.clock(), but it is deprecated since Python 3.3 and will be removed in Python 3.8.

There are better profiling tools like timeit and profile, however time.process_time() will measure the CPU time and this is what you're are asking about.

If you want to measure wall clock time instead, use time.time().

How do I get time of a Python program's execution?

The simplest way in Python:

import time
start_time = time.time()
main()
print("--- %s seconds ---" % (time.time() - start_time))

This assumes that your program takes at least a tenth of second to run.

Prints:

--- 0.764891862869 seconds ---

Measuring execution time of a function in C++

It is a very easy-to-use method in C++11. You have to use std::chrono::high_resolution_clock from <chrono> header.

Use it like so:

#include <chrono>

/* Only needed for the sake of this example. */
#include <iostream>
#include <thread>
    
void long_operation()
{
    /* Simulating a long, heavy operation. */

    using namespace std::chrono_literals;
    std::this_thread::sleep_for(150ms);
}

int main()
{
    using std::chrono::high_resolution_clock;
    using std::chrono::duration_cast;
    using std::chrono::duration;
    using std::chrono::milliseconds;

    auto t1 = high_resolution_clock::now();
    long_operation();
    auto t2 = high_resolution_clock::now();

    /* Getting number of milliseconds as an integer. */
    auto ms_int = duration_cast<milliseconds>(t2 - t1);

    /* Getting number of milliseconds as a double. */
    duration<double, std::milli> ms_double = t2 - t1;

    std::cout << ms_int.count() << "ms\n";
    std::cout << ms_double.count() << "ms\n";
    return 0;
}

This will measure the duration of the function long_operation.

Possible output:

150ms
150.068ms

Working example: https://godbolt.org/z/oe5cMd

How do I time a method's execution in Java?

There is always the old-fashioned way:

long startTime = System.nanoTime();
methodToTime();
long endTime = System.nanoTime();

long duration = (endTime - startTime);  //divide by 1000000 to get milliseconds.

How do you measure the time a function takes to execute?

The best way to do that on an embedded system is to set an external hardware pin when you enter the function and clear it when you leave the function. This is done preferably with a little assembly instruction so you don't skew your results too much.

Edit: One of the benefits is that you can do it in your actual application and you don't need any special test code. External debug pins like that are (should be!) standard practice for every embedded system.

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