> On Mar 1, 2017, at 12:59 PM, Lucas Clemente Vella <[email protected]> wrote:
>
> I have a parallel AIJ matrix and I know exactly which element belongs to each
> one of the 4 submatrices blocks I want to use to solve the linear system. The
> blocks are not strided, because they have different number of elements.
>
> I understand that I must use PCFieldSplitSetIS(), since
> PCFieldSplitSetFields() is only for strided blocks. What I don't understand
> is how to create the IS structure I must pass to it.
>
> Each matrix coefficient is identified by a pair (i, j), but on IS creation
> functions, like ISCreateGeneral() and ISCreateBlock(), I am supposed to
> provide a one dimension set of indices. How does these indices relates to the
> matrix coefficients?
PCFieldSplitSetIS() always indicates SQUARE blocks along the diagonal of the
original matrix. Hence you need only one IS to define a block, you don't need
one for the columns and one for the rows. The IS is telling what rows AND
columns you want in the block.
> Also, ISCreateGeneral() seems to create a single block, and ISCreateBlock()
> seems to create multiple blocks of the same size.
ISCreateBlock() does not create multi blocks, it creates a single IS that
has "block structure", for example 0,1, 3, 4, 6, 7, 9,10, ....
> How to create multiple blocks with different sizes?
ISCreateGeneral().
>
> Thanks.
>
> --
> Lucas Clemente Vella
> [email protected]
