# whats is presice compute time in matlab

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Abolfazl Nejatian am 30 Jan. 2020
Hi every one,
i just want to check different parts of my code's computation time, so i use tic toc function.
the results are varied than i use this loop and find out strange results
for i=1:13
tic,toc;
end
• Elapsed time is 0.000037 seconds.
• Elapsed time is 0.000013 seconds.
• Elapsed time is 0.000014 seconds.
• Elapsed time is 0.000013 seconds.
• Elapsed time is 0.000121 seconds.
• Elapsed time is 0.000002 seconds.
• Elapsed time is 0.000001 seconds.
• Elapsed time is 0.000001 seconds.
• Elapsed time is 0.000001 seconds.
• Elapsed time is 0.000000 seconds.
• Elapsed time is 0.000000 seconds.
• Elapsed time is 0.000000 seconds.
• Elapsed time is 0.000000 seconds.
the question is these different elapsed times how created?
and why the elapsed time sequence is descending?
kind regard,
Abolfazl
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### Antworten (1)

Bjorn Gustavsson am 30 Jan. 2020
These fluctuations are "kind of expected", your computer does a lot of other stuff in addition to running matlab which gives the elapsed time a little bit of variation. To get good estimates of the differences in running-times of code-snippets the general rule is to take the average time over some reasonable number of itterations.
For your case a better option might be to run your code with profiling on - that will give you a very precise tracking of what lines takes how much time, chech the help and documentation for profile.
Matlab used to have functions for cpu-time used, but that was discontinued after multithreading and other modern capacities was introduced.
HTH
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Abolfazl Nejatian am 4 Feb. 2020
dear Walter,
i try the timeit() function and it was work for me.
actually i need to evaluate small time from a WebSocket server which are in the millisecond range.
but most of the time evaluation method didn't work efficiently and i finally send a big bunch of data and evaluate the processing time by dividing data size to the total computation time to understanding the computation time per sample.

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