Hi all, I am using mpich-3.0.4 on Mac os x version 10.7.5 to run FLASH code. It works fine in the beginning of the run and then I got the following error: Fatal error in MPI_Comm_create: Other MPI error, error stack: MPI_Comm_create(600).................: MPI_Comm_create(comm=0x84000002, group=0xc8001349, new_comm=0x7fff606a8614) failed MPI_Comm_create(577).................: MPIR_Comm_create_intra(241)..........: MPIR_Get_contextid(799)..............: MPIR_Get_contextid_sparse_group(1146): Cannot allocate context ID because of fragmentation (169/2048 free on this process; ignore_id=0) Fatal error in MPI_Comm_create: Other MPI error, error stack: MPI_Comm_create(600).................: MPI_Comm_create(comm=0x84000002, group=0xc80012b6, new_comm=0x7fff670cc614) failed MPI_Comm_create(577).................: MPIR_Comm_create_intra(241)..........: MPIR_Get_contextid(799)..............: MPIR_Get_contextid_sparse_group(1146): Cannot allocate context ID because of fragmentation (316/2048 free on this process; ignore_id=0) Fatal error in MPI_Comm_create: Other MPI error, error stack: MPI_Comm_create(600).................: MPI_Comm_create(comm=0x84000004, group=0xc800000e, new_comm=0x7fff629d5614) failed MPI_Comm_create(577).................: MPIR_Comm_create_intra(241)..........: MPIR_Get_contextid(799)..............: MPIR_Get_contextid_sparse_group(1146): Cannot allocate context ID because of fragmentation (2020/2048 free on this process; ignore_id=0) Fatal error in MPI_Comm_create: Other MPI error, error stack: MPI_Comm_create(600).................: MPI_Comm_create(comm=0x84000002, group=0xc8000020, new_comm=0x7fff639ae614) failed MPI_Comm_create(577).................: MPIR_Comm_create_intra(241)..........: MPIR_Get_contextid(799)..............: MPIR_Get_contextid_sparse_group(1146): Cannot allocate context ID because of fragmentation (2002/2048 free on this process; ignore_id=0 Is there a way to fix that ? Thanks, Reem