[petsc-users] Question about Nested matrices

[Jed Brown]

Alejandro D Otero <aotero at fi.uba.ar> writes:

> Hi all,
> I am trying to nest to square matrices to form a rectangular one with dims
> 2n x n (with n the size of the square matrices)
> I want the two matrices to have interlaced rows so I passed the following 2
> list of indices to MatCreateNest:
>
> [[ 0  2  4  6  8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46
> 48]
> [ 1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
> 49]]
>
> And we get the following error message:
> Global sizes (25,25) of nested submatrix (0,0) do not agree with space
> defined by index sets (50,25)

Looks like the isglobal.row[i] index set has dimension 50 instead of 25.

#if defined(PETSC_USE_DEBUG)
  for (i=0; i<vs->nr; i++) {
    for (j=0; j<vs->nc; j++) {
      PetscInt m,n,M,N,mi,ni,Mi,Ni;
      Mat      B = vs->m[i][j];
      if (!B) continue;
      ierr = MatGetSize(B,&M,&N);CHKERRQ(ierr);
      ierr = MatGetLocalSize(B,&m,&n);CHKERRQ(ierr);
      ierr = ISGetSize(vs->isglobal.row[i],&Mi);CHKERRQ(ierr);
      ierr = ISGetSize(vs->isglobal.col[j],&Ni);CHKERRQ(ierr);
      ierr = ISGetLocalSize(vs->isglobal.row[i],&mi);CHKERRQ(ierr);
      ierr = ISGetLocalSize(vs->isglobal.col[j],&ni);CHKERRQ(ierr);
      if (M != Mi || N != Ni) SETERRQ6(PetscObjectComm((PetscObject)sub),PETSC_ERR_ARG_INCOMP,"Global sizes (%D,%D) of nested submatrix (%D,%D) do not agree with space defined by index sets (%D,%D)",M,N,i,j,Mi,Ni);
      if (m != mi || n != ni) SETERRQ6(PetscObjectComm((PetscObject)sub),PETSC_ERR_ARG_INCOMP,"Local sizes (%D,%D) of nested submatrix (%D,%D) do not agree with space defined by index sets (%D,%D)",m,n,i,j,mi,ni);
    }
  }
#endif
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