On Dec 3, 2004, at 5:54 AM, Gabriel Antoine Louis Paillard wrote:
> I would like to know, if we can invoke the MPI_Comm_spawn function,
> just as a root process ?
Not quite sure what you mean here by "just as a root process"...?
The MPI_COMM_SPAWN call is collective over all processes in the
communicator. Hence, every process in the communicator must call
COMM_SPAWN.
If you only want one communicator to call COMM_SPAWN, then you can use
the communicator MPI_COMM_SELF (which, by definition, only includes the
local process) as the argument to MPI_COMM_SPAWN. But then note that
only that one parent process will be able to communicate with the
spawned children.
> And if not, how can we proceed to call
> MPI_Comm_spawn from every rank of a group with differents arguments ?
As per MPI-2 p84, the command, argv, maxprocs, and info arguments to
MPI_COMM_SPAWN are only significant in the root process. The root and
comm arguments must be the same across all processes in the
communicator. The intercomm and array_of_errorcodes arguments will be
filled by MPI upon return from MPI_COMM_SPAWN in all processes in the
communicator.
--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
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