Right now, it success for Comm but fails for Win and File. IMHO, all should success, this should be a way for users to ask the implementation "please, reset the info hints to whatever the defaults are". If you decide they should fail, then the Comm case needs a fix to generate an error. $ mpicc comm_set_info.c $ ./a.out $ mpicc win_set_info.c $ ./a.out Fatal error in MPI_Win_set_info: Invalid argument, error stack: MPI_Win_set_info(126): MPI_Win_set_info(win=win=0xa0000000, info=MPI_INFO_NULL) failed MPI_Win_set_info(82).: Null MPI_Info $ mpicc file_set_info.c $ ./a.out Fatal error in PMPI_Info_dup: Invalid argument, error stack: PMPI_Info_dup(149): MPI_Info_dup(MPI_INFO_NULL, newinfo=0x7fff58b899c4) failed PMPI_Info_dup(108): Null MPI_Info PS: Perhaps you have an easy fix for the error message (PMPI -> MPI) in the last one? -- Lisandro Dalcin --------------- CIMEC (UNL/CONICET) Predio CONICET-Santa Fe Colectora RN 168 Km 472, Paraje El Pozo 3000 Santa Fe, Argentina Tel: +54-342-4511594 (ext 1016) Tel/Fax: +54-342-4511169