On Mon, 2008-08-04 at 04:17 -0500, Matthew Knepley wrote:

On Mon, Aug 4, 2008 at 3:14 AM, Ahmed El Zein <[email protected]> wrote:

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I am working on a project where I would like to copy a sparse matrix in CSR format.

I have tried MatGetRow() which works OK but I would really like to get pointers to the 3 arrays directly.

I also tried MatGetRowIJ() which allows me to get the i and j arrays but I can't see how to access the nonzero elements.

You can use MatGetArray(). Thanks. The man page states that: The result of this routine is dependent on the underlying matrix data structure, and may not even work for certain matrix types.

How do I find out which matrix types support it? and is there a method that works across all matrix types? Thanks, Ahmed

Matt

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and finally I attempted to access the arrays directly like this: Mat_SeqAIJ *a = (Mat_SeqAIJ*)A->data; MatScalar *val = a->a; PetscInt *ptr = a->i; PetscInt *ind = a->j;

However when accessing directly I get different values for ptr and SIGSEGV when accessing val or ind.

also I get a bogus number for a->nz (134630032 instead of 21)

What is the correct way to get the number of nonzeros?

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Can someone please explain when I am doing wrong?

Ahmed