PETSc does NOT use a 2D partition. You need to get that concept out of your head.
On Wed, Aug 8, 2012 at 3:09 PM, Jinquan Zhong <jzhong at scsolutions.com>wrote: > Satish, > > I looked at > > http://www.mcs.anl.gov/petsc/petsc-current/src/snes/examples/tutorials/ex5s.c.html > where > > MatCreateAIJ(PETSC_COMM_WORLD,rend-rstart,rend-rstart,N,N,5,0,0,0,&J); > > was used to create J (N,N) with local J dimensioned as > (rend-rstart,rend-rstart). > > For my application, I have LDA=LDB=3 and N=9 in the following > > ierr = MatCreateAIJ(PETSC_COMM_WORLD,LDA,LDB,N,N,LDA,0,0,0,&A); > CHKERRQ(ierr); > > I got the following error message: > > [0]PETSC ERROR: --------------------- Error Message > ------------------------------------ > [0]PETSC ERROR: Nonconforming object sizes! > [0]PETSC ERROR: Sum of local lengths 27 does not equal global length 9, my > local length 3 > likely a call to VecSetSizes() or MatSetSizes() is wrong. > > > It does NOT appear PETSc had the 9x9 matrix. It tried to build 27*27 > since I am using 9 procs. Is there a way to resolve this local size and > global size issue? > > Thanks, > > Jinquan > > > > -----Original Message----- > From: petsc-users-bounces at mcs.anl.gov [mailto: > petsc-users-bounces at mcs.anl.gov] On Behalf Of Satish Balay > Sent: Wednesday, August 08, 2012 1:45 PM > To: PETSc users list > Subject: Re: [petsc-users] Customizeing MatSetValuesBlocked(...) > > 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 > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120808/063e1bd0/attachment.html>
