Reading a Sparse matrix in CRS format from a function to be used in parallel linear solvers

[Matthew Knepley]

On 1/31/07, #DOMINIC DENVER JOHN CHANDAR# <DOMI0002 at ntu.edu.sg> wrote:
>
>  Hi,
>
>        I have a function which creates a sparse matrix following a certain
> eqn and returns a pointer to the row, column index and the value of a sparse
> matrix (CRS- form).
> i   j   val
> 1  1  1.0
> 2  2  1.0
> 2  3  -1.5..
> so on...
>
>  The matrix *may not **have a definite pattern* like the one we see for
> tridiagonal or pentadiagonal matrices or the test cases (linear solvers)
> cited in the petsc documentation. Now, i would like to use the linear
> solvers in petsc to solve the system of equations. I do not want to write
> that sparse matrix into a file and read it into petsc since it may be
> huge.I would like to call that function from petsc and would return the
> pointer to i j and val and insert values of this sparse matrix using
> MatSetValues in parallel. How can I achieve this ?
>

We do not have CRS format as it is not a very space efficient format. Most
of our formats are row-oriented. I suggest
looking at the example for MatSetValues() and trying to rework the
discretization function to directly call this. Most
discretizations naturally generate row-by-row values or even blocks like
FEM. Even totally nustructured stuff from
economics is row-by-row.

  Thanks,

    Matt

Cheers,
> Dominic
>
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