> block size > 1 really only makes sense if the block size is really greater > than one. So if A has blocks of size 3 you should create A as BAIJ and thus > never need to call the convert routine.
Unfortunately A is not created by my part of the program and comes with blocksize 1. > > You can also set the block size for AIJ matrix to 3 and use > MatInvertBlockDiagonal() on that matrix and not use the BAIJ matrix. If I run: ierr = MatSetBlockSize(A, 3); CHKERRQ(ierr); It doesn’t work for me. I get: [1;31m[0]PETSC ERROR: --------------------- Error Message -------------------------------------------------------------- [0;39m[0;49m[0]PETSC ERROR: Arguments are incompatible [0]PETSC ERROR: Cannot change block size 1 to 3 [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting. [0]PETSC ERROR: Petsc Release Version 3.6.3, Dec, 03, 2015 . . What are the constraints for blocksize?