Assertion message thrown by ParMetis


I have been in trouble with an error message from ParMetis-3.1.1 used for a physics application (using PETSc) running on Cray XT systems.

The application program splits all MPI PEs into 32 disjoint MPI groups (so 32 MPI communicators are created) and calls iterative linear solver for each MPI group. During the solution ParMetis is called by each group in order to improve load balance within. The code terminates with the following Assertion message from each group when using more than 128 processors (more than 4 PEs per MPI group). Interestingly, the message is thrown by the last PE of each group; if 256 PEs are used, the message is thrown by 8th PE of each group.

Do you have any idea with the message below? It might be PETSc's bug, but I want to make sure when this problem occurs and what I should investigate.

Thank you,


[ 7] ***ASSERTION failed on line 34 of file match.c: wspace->nlarge > graph->xadj[graph->nvtxs]
: (repeats 32 times)

RE: I believe this is due to the

I believe this is due to the fact that one of the processors end up having no edges. Will be fixed soon.