MATLAB: Tic toc inside a timeit

MATLABtic toctimeit

Hi,
I have a function "test". Inside this test function, I have a for loop that goes from 1 to N. Since I want to know the average time for each iteration, I put tic /toc, and a variable called "Time_for" will give me the average time, as you can see in the code below
test(x)  
tic  
  for i=1:N
      some operations
      % code
    end
  Time_for=toc/N % this result is displayed in the command window, and not saved as an output of the function
Now, I want to compute the time execution of the function. For this purpose, in the main of the program, I use the timeit function, as you can see below
f=@()test(x);
time_function=timeit(f);
My problem is that, when I run timeit, the variable "Time_for", that should just be displayed only once, it is actually displayed 10 times. And for each of these 10 times, the value slightly changes.
Why the toc function, inside a timeit, is computed multiple times?
Best,
Maria

Best Answer

I've never tried outputting to screen in a function wrapped in a timeit call, but I suspect the reason is simply because timeit runs your function multiple times in order to give a more accurate estimate of the function time than if you just ran it once with a tic toc. So if you output to the screen in your function it will likely do it however many times timeit runs your function.
Before timeit I used to create my own for loop, call my function many times and take an average, make sure each time had equal conditions and all that, but now timeit takes care of that for you.
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