It comes from here:
https://bitbucket.org/petsc/petsc/commits/c10200c1442b553b7ad65c70101560db4fa22e78 If we ask for more than 1 matrix, it dispatches to MatGetSubMatrices_MPIAIJ_SingleIS() but then fails here https://bitbucket.org/petsc/petsc/annotate/2e559809f9aee9c95ee79eb0939630cfe5502c8d/src/mat/impls/aij/mpi/mpiov.c?at=master&fileviewer=file-view-default#mpiov.c-1306 because ismax > 1. I think the ismax check needs to move up to here https://bitbucket.org/petsc/petsc/annotate/2e559809f9aee9c95ee79eb0939630cfe5502c8d/src/mat/impls/aij/mpi/mpiov.c?at=master&fileviewer=file-view-default#mpiov.c-2012 but I don't know for sure. Please fix this since it is breaking PyLith. Matt -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
