how to reduce the time of calling functions

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Qiandong Dong 2019-11-23

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https://ww2.mathworks.cn/matlabcentral/answers/492691-how-to-reduce-the-time-of-calling-functions

回答： jeewan atwal 2019-11-23

采纳的回答： Walter Roberson

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Answer 1

Walter Roberson 2019-11-23

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2/3 of the time is spent executing obj() which is not a Mathworks supplied function. You should investigate obj() to see how it could be sped up.

1/3 of the time is spent executing squeeze(), which is a Mathworks supplied function. As you are calling it many times in a loop, chances are good that you know which dimensions are expected to be singular, and in that situation there is a fairly strong chance that you can replace the call to squeeze() with a call to reshape() which would be more efficient because it would not need to do tests on the dimensions. The savings are probably not all that high though.

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Answer 2

jeewan atwal 2019-11-23

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编辑：jeewan atwal 2019-11-23

If you are callng MATLAB default functions, then, you cant do much as MATLAB default functions are very well optimized.

However, If you have created some funtions by yourself, then you need to optimize those functions to speed up the things.

Large For loops make MATLAB scripts slow.

If you have large For loop in the functions scripts, then to avoid those For loops you can use MATLAB vectorisation techinques to speed up things.

Hope this helps

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jeewan atwal 2019-11-23

I am not claiming that it is always faster. But at least in my problems, i found it faster than for loop. Could you please share any example where vectorisation was slow compared to for loop.