Hello, I have a range of local input data indices that I want to use for row indexing, say { 3, 4, 6}.
For that, I create a matrix with a local number of rows of 3 and map the indices {3, 4, 5} to these rows. I create an index set: ISCreateGeneral(comm, myIndizes.size(), myIndizes.data(), PETSC_COPY_VALUES, &ISlocal); ISSetPermutation(ISlocal); ISInvertPermutation(ISlocal, myIndizes.size(), &ISlocalInv); ISAllGather(ISlocalInv, &ISglobal); // Gather the IS from all processors ISLocalToGlobalMappingCreateIS(ISglobal, &ISmapping); // Make it a mapping MatSetLocalToGlobalMapping(matrix, ISmapping, ISmapping); // Set mapping for rows and cols The InvertPermutation is required because, well, it seems that the direction the mapping stuff works in PETSc. Now I can use MatSetValues local to set rows {3, 4, 5} and actually set the local rows {1, 2, 3}. The problem is that the range of data vertices is not always contiguous, i.e. could be {3, 4, 6}. This seems to be not a permutation of PETSc, therefore ISSetPermutation fails and subsequently ISInvertPermutation. How can I still create such a mapping, so that: 3 -> 1 4 -> 2 6 -> 6 row 5 is unassigned and will never be addressed. Thanks! Florian