On Wed, 8 Aug 2012, Jed Brown wrote: > On Wed, Aug 8, 2012 at 2:25 PM, Jinquan Zhong <jzhong at > scsolutions.com>wrote: > > > If I understand you correctly, ScaLAPACK blocks don't have anything to do > > with the sparse matrix structure.**** > > > > ** ** > > > > > > ****************************************************************************************************************************************** > > **** > > > > ** ** > > > > You are correct. What I meant was how to define the diagonal and > > off-diagonal parts of each submatrix matrix A (LDA, LDB). For example, in > > the following matrix,**** > > > > ** ** > > > > *Proc0* *Proc1* *Proc2***** > > > > 1 2 0 | 0 3 0 | 0 4**** > > > > *Proc0* 0 5 6 | 7 0 0 | 8 0**** > > > > 9 0 10 | 11 0 0 | 12 0**** > > > > -------------------------------------**** > > > > 13 0 14 | 15 16 17 | 0 0**** > > > > *Proc3* 0 18 0 | 19 20 21 | 0 0 <=== owned by Proc 5**** > > > > 0 0 0 | 22 23 0 | 24 0**** > > > > -------------------------------------**** > > > > *Proc6* 25 26 27 | 0 0 28 | 29 0**** > > > > 30 0 0 | 31 32 33 | 0 34**** > > > > ** ** > > > > I am not sure how to fill out the values for d_nz, d_nnz,o_nz, o_nnz > > peoperly for the subblock (0 0 ;0 0; 24 0) owned by Proc 5 since it was > > based on diagonal and off-diagonal parts. > > > > Throw your 2D block cyclic nonsense out the window. These are sparse > matrices and that layout would be terrible. Logically permute your matrices > all you want, then define a global ordering and chunk it into contiguous > blocks of rows (no partition of columns). Work this out with a pencil and > paper. You should have a function that translates row/column pairs from > your ordering to our ordering. Now compute the sparsity pattern in the new > ordering. (Usually you can figure this out on paper as well.) Then > preallocate and call MatSetValues() with the new (row,column) locations. >
also check the 'example usage' at: http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateAIJ.html Satish
