Concatenating large matrices - out of memory

Question

John 2013-3-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/66856-concatenating-large-matrices-out-of-memory

采纳的回答： Matt J

I have four 4096x4096 sparse matrices namely A, B, C, and D and they only have elements on the diagonal.

I tried to make a matrix X = [ A B; C D] which is 8192x8192 but I get an out of memory error.

Essentially, I need to multiply X with a 8192x1 vector Y.

Is there a more sophisticated way to do this?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt J 2013-3-12

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/66856-concatenating-large-matrices-out-of-memory#answer_78302

编辑：Matt J 2013-3-12

在 MATLAB Online 中打开

X=[sparse(A),sparse(B);sparse(C), sparse(D)];
result = X*Y;

Or,

a=diag(A);
b=diag(B);
c=diag(C);
d=diag(D);
   y1=Y(1:4096);
   y2=Y(4097:end);
   result = [a.*y1+b.*y2; c.*y1 + d.*y2];

2 个评论
显示无隐藏无

John 2013-3-12

Thanks but for your first solution, A, B , C, and D are already sparse. Does it change anything if you apply the sparse function again when it's being concatenated.

Matt J 2013-3-12

Are you sure they are already sparse? Or, are you sure the out-of-memory is coming from the statement X=[A B;C D]?

It doesn't make sense that diagonal sparse matrices of that size would give you any problems with memory. If you are on a 32 bit machine and you accidentally made those matrices non-sparse, I could see you getting such an error

请先登录，再进行评论。