Jeff Squyres wrote:
Perhaps we did that as a latency optimization...?
George / Brian / Galen -- do you guys know/remember why this was done?
On the surface, it looks like it would be ok to call progress and
check again to see if it found the match. Can anyone think of a
deeper reason not to?
If it is ok to check again, my next question is going to be how?
Because after looking at the code some more I found iprobe requests are
not actually queued. So can I just do another
MCA_PML_OB1_RECV_REQUEST_START on the init'd IPROBE_REQUEST after the
call opal_progress to force a search on the unexpected queue or do I
need to FINI the request and regenerate it again?
--td
On Jun 17, 2008, at 11:43 AM, Terry Dontje wrote:
I've ran into an issue while running hpl where a message has been
sent (in shared memory in this case) and the receiver calls iprobe
but doesn't see said message the first call to iprobe (even though it
is there) but does see it the second call to iprobe. Looking at
mca_pml_ob1_iprobe function and the calls it makes it looks like it
checks the unexpected queue for matches and if it doesn't find one it
sets the flag to 0 (no matches), then calls opal_progress and
return. This seems wrong to me since I would expect that the call to
opal_progress probably would pull in the message that the iprobe is
waiting for.
Am I correct in my reading of the code? It seems that maybe some
sort of check needs to be done after the call to opal_progress in
mca_pml_ob1_iprobe.
Attached is a simple program that shows the issue I am running into:
#include <mpi.h>
int main() {
int rank, src[2], dst[2], flag = 0;
int nxfers;
MPI_Status status;
MPI_Init(NULL, NULL);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
if (0 == rank) {
for (nxfers = 0; nxfers < 5; nxfers++)
MPI_Send(src, 2, MPI_INT, 1, 0, MPI_COMM_WORLD);
} else if (1 == rank) {
for (nxfers = 0; nxfers < 5; nxfers++) {
sleep(5);
flag = 0;
while (!flag) {
printf("iprobe...");
MPI_Iprobe(0, 0, MPI_COMM_WORLD, &flag, &status);
}
printf("\n");
MPI_Recv(dst, 2, MPI_INT, 0, 0, MPI_COMM_WORLD, &status);
}
}
MPI_Finalize();
}
--td
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