Reshaping is causing memory problem

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Saddam N Y
Saddam N Y 2024-2-5
评论： Saddam N Y 2024-2-6
Hello everyone,
I have 500 matrices of huge size of 40834 x 40834 and I would like to load them from mat files and then flatten them using the reshape function and later do some other things. However in the first flatteing operation I am getting a memory issue and Matlab aborts. How one could solve such a problem ? The code is below, here all Ki.mat are sparse matrices. Thank you.
i=1;
K_matrix_file = strcat('Matrices/K',num2str(i),'.mat');
load(K_matrix_file);
K_flatten = reshape(K_i,1,[]);
Saddam
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Matt J
Matt J 2024-2-5
编辑：Matt J 2024-2-5
Are the matrices in sparse format? If they are in non-sparse format and they loaded sucessfully, there's no reason the reshape operation should have breached memory limits, unless the matrix consumes most of your RAM.
Saddam N Y
Saddam N Y 2024-2-5
Sorry I updated the question to include the piece of code that produces the issue. The matrices are all in the sparse format.

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采纳的回答

Matt J
Matt J 2024-2-5
编辑：Matt J 2024-2-5
Don't make long sparse row vectors, as these do consume lots of memory. Work with column vectors instead:
K_flatten = K_i(:);
  2 个评论
Walter Roberson
Walter Roberson 2024-2-5
Ran in:
t0 = spalloc(1,0,2);
t1 = spalloc(1,100,2);
t2 = spalloc(1,101,2);
whos t0 t1 t2
Name Size Bytes Class Attributes t0 1x0 40 double sparse t1 1x100 840 double sparse t2 1x101 848 double sparse
t1(1,100) = 1;
t2(1,100) = 1;
whos t1 t2
Name Size Bytes Class Attributes t1 1x100 840 double sparse t2 1x101 848 double sparse
t1(1,50) = 2;
t2(1,50) = 2;
whos t1 t2
Name Size Bytes Class Attributes t1 1x100 840 double sparse t2 1x101 848 double sparse
In short, a sparse row vector takes 8 bytes plus 8 bytes per column plus 16 bytes per non-zero.
This is a more than the equivalent non-sparse row vector, which would take 8 bytes per column.
Saddam N Y
Saddam N Y 2024-2-6
Thank you very much for your answer !!

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