[petsc-users] Using MatCreateSBAIJ and MatZeroRowsColumns in parallel

[Karthikeyan Chockalingam - STFC UKRI]

Hello,



I have system matrix which is symmetric and thought I could make use of MatCreateSBAIJ. I don’t understand how to set the blocksize bs. I believe it has taken into account, when having multiple components/dofs per node.



(i)          Currently, I have only one scalar field to solve so I set bs = 1 as below. Is it correct?


      ierr = MatCreateSBAIJ(PETSC_COMM_WORLD, 1, PETSC_DECIDE, PETSC_DECIDE, N, N, d_nz, PETSC_NULL, o_nz, PETSC_NULL, &A); CHKERRQ(ierr);

   ierr = MatCreateVecs(A, &right, &left);CHKERRQ(ierr);



(ii)         If you multiple components/dofs per node, say 2, is the then block size = 2?



(iii)        To apply homogenous Dirichlet boundary condition, I make use of MatZeroRowsColumns. It works in serial but while applying in parallel the following error is thrown,



[0]PETSC ERROR: No method zerorowscolumns for Mat of type mpisbaij



      How do I fix it?



(iv)                           Is there performance again, when using MatCreateSBAIJ for large symmetric system matrix? I read there is more communication involved.

Best,
Karthik.



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