[petsc-users] dynamic matrix type & dense matrix.

[Jed Brown]

Mark Adams <mfadams at lbl.gov> writes:

> MatSetup was the issues: this seems to work with and w/o -mat_type dense:
>
>            call MatCreate(solver%comm,solver%schur,ierr);
>            call
> MatSetSizes(solver%schur,nloc,nloc,PETSC_DECIDE,PETSC_DECIDE,ierr)
>            call MatSetType(solver%schur,MATAIJ,ierr)
>            call
> MatSeqAIJSetPreallocation(solver%schur,nloc,PETSC_NULL_INTEGER,ierr)
>            call
> MatMPIAIJSetPreallocation(solver%schur,nloc,PETSC_NULL_INTEGER,i,PETSC_NULL_INTEGER,ierr)
>            call MatSetFromOptions(solver%schur,ierr)

Changing the matrix type (-mat_type) after calling the preallocation
functions above will lose that preallocation information.  Better to
call MatSetFromOptions first.

>            call MatSetup(solver%schur,ierr)

How is A->preallocated being set?  MatSetValues checks for it and
MatSetType makes it false.  We need to find out why so that users don't
stumble over this.
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