Accumarray application for rectangle submatices

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Grigorii Nefedov 2021-8-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/893602-accumarray-application-for-rectangle-submatices

评论： Matt J 2021-8-6

Is there an elegant way to exclude the for loop from the following function using the accumarray function, for example?

function K = accum(K_size, ...
    Pi0, Pi1, Pj0, Pj1, ...
    Ki0, Ki1, Kj0, Kj1, ...
    psf_arr, psf_ind)
K = zeros(K_size);
for s = 1 : numel(psf_ind)
    
    K( Ki0(s) : Ki1(s), Kj0(s) : Kj1(s) ) = ...
        K( Ki0(s) : Ki1(s), Kj0(s) : Kj1(s) ) + ...
    psf_arr( Pi0(s) : Pi1(s), Pj0(s) : Pj1(s), psf_ind(s) );
end
end

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Jan 2021-8-6

编辑：Jan 2021-8-6

@Grigorii Nefedov: Please provide some input data with usual sizes. It matters, if this hould be optimized for millions of loops over small blocks or some loops over huge blocks.

It is tedious to guess, how usual inputs looks in oyur code, but you should be able to create some "meaningful" data with some calls of rand().

Do you want to get an elegenat code, or a fast one? I do not see how avoiding a loop is useful in general.