De-allocation un-used spalloc

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Pete sherer 2018-2-6

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https://ww2.mathworks.cn/matlabcentral/answers/381076-de-allocation-un-used-spalloc

评论： Jan 2018-2-6

Hi

For the S = spalloc(m,n,nz); function where users can pre-allocate non-zero elements, I wonder if there's a way to de-allocate unused elements. For example S = spalloc( 100000, 500, 2e6); and I only allocate 1e6 element. Is there away to shrink down S to only 1e6 elements?

Thanks

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Answer 1

Jan 2018-2-6

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https://ww2.mathworks.cn/matlabcentral/answers/381076-de-allocation-un-used-spalloc#answer_303701

编辑：Jan 2018-2-6

在 MATLAB Online 中打开

I'd try it by:

S = spalloc( 100000, 500, 2e6);
... fill in 1e6 values
T = spalloc( 100000, 500, 1e6);
T = S;

Inside the mex level you could use mxRealloc to shrink the reserved block of memory for the data and indices, but even then it is not guaranteed, that the same start address is used or that the free'd part of the memory is given back to the operating system directly or later. Therefore I assume the creation of a new smaller array and copy of the values is not very much worse. But if you are very low on memory, the temporary creation of another array is a problem.