MATLAB: Calculation of a sparse matrix

matrixsparseurgent

I have a very large matrix, with 3,26,041 rows and columns. I tried doing the simple sparse function for calculating it. But it returns an output as "out of memory" . I have a 64 bit system with 4gb ram. Is there anyway that i can calculate it or do i need a better system ? Can anyone please help, I am new to matlab and hence require urgent help..

Best Answer

Sorry if I am saying what you already know, but the way you have defined A, it is decidedly non-sparse. You should not use the pre-allocation to zeros.

You should initialize the matrix A using the "sparse" command, which will define the indexing into A, without allocating memory for the elements. Then you can fill it in with your loops. Hopefully, there are few enough non-zero elements in the matrix to fit into memory.

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MATLAB: Allocate a big matrix

Use spalloc() specifying the number of expected non-zero values.

Sparse matrices are more efficiently filled working down columns than across rows.

10^5 by 10^4 is 10^9, just under 1 giga-entries. If you were to use the default double() datatype, that would require 8 gigabytes to store. Your preferences have been configured to not allow you to store matrices that large. If you have enough memory for this (and for the other arrays you are using) then you could change your preferences. And if you can get away with using something other than double precision, then create the array that way. For example,

A = zeros(10^5, 10^4, 'int16');

would take only 1/4 of the storage.

MATLAB: Memory usage in sparse matrix

Try just:

 >> sparse(80000,80000)

to avoid the temporary allocation of a 80000^2 non-sparse zeros array.

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MATLAB: Allocate a big matrix

MATLAB: Memory usage in sparse matrix

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