[mpich-discuss] Joining a job from a process without mpiexec parent

[Michael.Stokes at uah.edu]

Dmitriy,

I've written a server and client code example and compiled it using 
MPICH 3.2 using MPI_Comm_{accept,connect}() to see if MPICH 3.2 will 
form a intercommunicator between the two processes without using a 
launcher {mpiexec,mpirun}.  Before I started, I read the instructions ( 
MPI Specs 3.1 section 10.5.2). It states

"A high-quality implementation will allow any process (including those 
not started with a
“parallel application” mechanism) to become an MPI process by calling 
MPI_INIT. Such
a process can then connect to other MPI processes using the 
MPI_COMM_ACCEPT and
MPI_COMM_CONNECT routines, or spawn other MPI processes. MPI does not 
mandate
this behavior, but strongly encourages it where technically feasible."

Case 1) With the server and client run directly from the command-line 
the server executes down to the MPI_Comm_accept() call as anticipated, 
but when the port name is entered into the client process, it dies on 
MPI_Comm_connect() with the error ...

match_arg (utils/args/args.c:159): unrecognized argument pmi_args
[mpiexec at Que] HYDU_parse_array (utils/args/args.c:174): argument 
matching returned error
[mpiexec at Que] parse_args (ui/mpich/utils.c:1596): error parsing input array
[mpiexec at Que] HYD_uii_mpx_get_parameters (ui/mpich/utils.c:1648): unable 
to parse user arguments
[mpiexec at Que] main (ui/mpich/mpiexec.c:153): error parsing parameters

Case 2) When I run the server directly from the command-line and launch 
the client using mpirun, the same sort of error messages emerge but this 
time from the server.  Since the server blocks on the accept() call, the 
client must be successful in sending something to the server.  But 
apparently not what it is expecting.

So my conclusion is that MPICH is attempting to support the Singleton 
process, but either has a bug or there might be an installation issue on 
my end.

Hopefully someone can help sort this.

--Mike

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