Hi there, I'm using an external matrix solver library which is resulting in error, either in mpi_comm_dup or mpi_comm_split. This happens after rebuilding the matrix and calling the solver many times (hundreds of times or more), during which the solver object is destroyed and recreated. These routines are never called from my code. And as far as I can see in the solver source, there are corresponding calls to mpi_comm_free, but it's entirely possible that my assessment is incorrect. The MPI error messages and strack trace printed upon crash are quite brief, and I'm finding it difficult to tackle this issue. What I'd like to determine first is whether fault is on my side (e.g. perhaps I'm not calling the clean-up routines properly). Is there a way to find out how many context id's are in use at a given point? -- Ubuntu 12.04, mpich2 1.4, gcc/gfortran. The linear solver is SuperLU_dist 2.5. Many thanks, Jack