"Zhang, Junchao via petsc-users" <petsc-users@mcs.anl.gov> writes:
> Perhaps PETSc should have a MatGetRemoteRow (or > MatGetRowOffDiagonalBlock) (A, r, &ncols, &cols, &vals). MatGetRow() > internally has to allocate memory and sort indices and values from > local diagonal block and off-diagonal block. It is totally a waste in > this case -- users do not care column indices and the local block. > With MatGetRemoteRow(A, r, &ncols, NULL, &vals), PETSc just needs to > set an integer and a pointer. I'm not wild about the resulting programming model, which is so intimately tied to PETSc *AIJ storage conventions yet also likely not efficient for operations like SOR. Perhaps PETSc MatSOR should be taught about a supplemental diagonal, such as produced by the "l^1" scheme?
