call function - slow

Question

Alessandro D 2018-9-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/419622-call-function-slow

回答： Sambit Senapati 2018-9-21

Dear users, I am struggling with optimizing the code for a project of mine and I am following the suggested practice of breaking my code in small parts with separate functions. However when I do this I get a significant loss in execution speed. Please consider the following two examples:

A)

function y = fun1(a,params)
%params is structure with several variables
b = a*2;
y = b+1;
end %end fun1

compared to

B)

function y = fun1(a,params)
%params is structure with several variables
b = fun2(a,params);
y = b+1;
end %end fun1
function b = fun2(a,params)
b = a*2;
end %end fun2

(B) is easier to maintain but for my application is 20/30% slower. (Of course the example above is a toy example). One reason could be that I have to pass to fun2 "params" which is a big structure. But using globals would be even worse, are there any other (fast) ways? Thanks!

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Guillaume 2018-9-18

编辑：Guillaume 2018-9-18

If params is not modified by fun2, then passing it to fun2 is just a pointer copy (8 bytes) regardless of the size of params, and so will not cause any noticeable slowdown. If params does get modified in fun2, then you will incur a copy of the whole content which could take some time if it's big.

I think you need to get into more details of what actually happens in your fun2.

Alessandro D 2018-9-18

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Dear guys, thanks for your answers. These are some more detail. In fun2 I need to unpack the structure params. But params itself is not modified

function y = fun1(a,params)
%params is structure with several variables
b = fun2(a,params);
y = b+1;
end %end fun1
function b = fun2(a,params)
agrid = params.agrid;
zgrid = params.zgrid;
na = params.na;
nz = params.nz;
uf = params.uf;
tranZ = params.tranZ;
amin = min(agrid); amax = max(agrid);
%Do some operations with agrid, zgrid etc.
b = a*2 + agrid.^2;
end %end fun2

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Answer 1

Sambit Senapati 2018-9-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/419622-call-function-slow#answer_337744

Please go through the this link which describes about performance of different types of function calls. This may help you to figure out why your code is slow.