[petsc-users] Insering rows vs inserting columns

[Bartłomiej W]

That helped.

I am also wondering about SEQ and MPI matrices, do they differ more than just in way of allocating data? When I run a small problem on 2 processes on single machine, it slows down greatly if I use 

MatCreateMPIAIJ(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,n,n,5,PETSC_NULL,5,PETSC_NULL,&L);

As I get mallocs during mat assembly while o_nz and d_nz are set to 5 where 5 is max nonzeros per whole row. I also get stash:0 assuring that values are set by correct process.

Any hints on this one?

Thank you

Regards
Bartek Wach
The order or the way the values are inserted shouldn't matter. As long
as the correct nozero structure is provided [with nnz] - there should
be no additional mallocs.

you can check with MatView() to see if the matrix is anyway different
in the 2 cases.

Satish

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