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matlabmatrixsparse-matrix

Sparse matrix storage space

I need to get the storage size of sparse matrix in amount of double numbers. I need to get this information in runtime.

Solution

  • The nonzero elements are stored, alongside with their row indices, so 

    nnz(x);

    is a good approximation, as it returns the number of nonzero elements.

    If your sparse matrix is getting unexpectedly big, you can check nnz to keep track of a bug which may result in overwriting a lot of zero elements.

    So the effectiveness of using sparse matrices can be also measured with

    s=size(m_sparse);
effectiveness = 1 - nnz(x)/(s(1)*s(2))