Is there any other function faster than sum(A,2) to get the sum of all rows?

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Nadatimuj
Nadatimuj 2022-6-26
评论： Walter Roberson 2022-6-27
Ran in:
a=zeros(6750);
h=zeros(6750,1);
tic;k=h-sum(a,2); toc
Elapsed time is 0.041132 seconds.
Is there any faster way than to use sum(A,2) to get the sums of the rows of a matrix? sum(A,2) seems to be slow for large matrices.
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Image Analyst
Image Analyst 2022-6-27
The Parallel Processing Toolbox is an add-on toolbox. You can ask for a free trial of it and see if the Parallel Processing Toolbox helps. I know some functions recognize if you have that toolbox and start parallel processes going on multiple CPU cores on your computer automatically.
Walter Roberson
Walter Roberson 2022-6-27
For sufficiently large matrices, addition is automatically handled by high performance parallel libraries. Using parfor or parfeval() will not improve performance compared to the automatic multi-core work that is done.

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回答（2 个）

Walter Roberson
Walter Roberson 2022-6-26
Switching to columns can improve performance as it allows better use of hardware cache.
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Nadatimuj
Nadatimuj 2022-6-26
Ran in:
Thanks for the suggestion. Did you mean this? Doesn't look like to save too much time...
a=zeros(6750);
h=zeros(1,6750);
tic;k=h-sum(a,1); toc
Elapsed time is 0.033019 seconds.

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MJFcoNaN
MJFcoNaN 2022-6-26
Ran in:
In general, the native functions are optimized sufficiently.
In certain cases, there may be some better way but in other parts of code. For example,
a=sparse(zeros(6750));
h=sparse(zeros(6750,1));
tic;k=h-sum(a,2); toc
Elapsed time is 0.003234 seconds.
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Nadatimuj
Nadatimuj 2022-6-26
Thanks, yes that's a good idea. However, originally I didn't use the sparse notation, I will check if using sparse will impact other parts of the code. Otherwise sparse conversion just here can take some time.

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