Dear MPI Forum, The description of the 'array_of_commands` parameter passed to 'MPI_Comm_spawn_multiple()' is not crystal clear IMHO. The standard simply states MPI_COMM_SPAWN_MULTIPLE(count, array_of_commands, ...) IN count number of commands (positive integer, significant to MPI only at root | see advice to users) IN array_of_commands programs to be executed (array of strings, significant only at root) Advice to users. The argument count is interpreted by MPI only at the root, as is array_of_argv. Since the leading dimension of array_of_argv is count, a non-positive value of count at a non-root node could theoretically cause a runtime bounds check error, even though array_of_argv should be ignored by the subroutine. If this happens, you should explicitly supply a reasonable value of count on the non-root nodes. (End of advice to users.) And the Fortran binding is MPI_COMM_SPAWN_MULTIPLE(COUNT, ARRAY_OF_COMMANDS, ...) INTEGER COUNT CHARACTER*(*) ARRAY_OF_COMMANDS(*) Intuitively, it seems obvious that 'array_of_commands' is an array of 'count' commands. That being said, the standard does not state that, and it is unclear whether 'array_of_commands' should be NULL-terminated (so to speak) or not. Back to the Fortran binding, the following prototype, which is somehow consistent with 'array_of_argv', could (help to) clear the confusion. The same comments also apply to the Fortran 2008 binding. CHARACTER*(*) ARRAY_OF_COMMANDS(COUNT) Gilles