Hello,
Gustavo Correa wrote:
I guess you need to provide buffers of char type to
MPI_Send and MPI_Recv, not NULL.
That was not the problem, I was anyway using message size 0, so then
it should be OK to give NULL as the buffer pointer.
I did find the problem now; it turns out that this was not at all due
to any bug in Open MPI, it was my program that had a bug; I used wrong
constant specifying the datatype. I used MPI_CHARACTER which I thought
would correspond to a char or unsigned char in C/C++. But now when I
checked the MPI standard it says that MPI_CHARACTER is for the Fortran
CHARACTER type. Since I am using C, not Fortran, I should use MPI_CHAR
or MPI_SIGNED_CHAR or MPI_UNSIGNED_CHAR. Now I have corrected my
program by changing MPI_CHARACTER to MPI_UNSIGNED_CHAR, and then it
works.
Sorry for reporting this as a bug in Open MPI, it was really a bug in
my own code.
/ Elias
Quoting Gustavo Correa <g...@ldeo.columbia.edu>:
I guess you need to provide buffers of char type to
MPI_Send and MPI_Recv, not NULL.
On Mar 16, 2014, at 8:04 PM, Elias Rudberg wrote:
Hi Ralph,
Thanks for the quick answer!
Try running the "ring" program in our example directory and see if
that works
I just did this, and it works. (I ran ring_c.c)
Looking in your ring_c.c code, I see that it is quite similar to my
test program but one thing that differs is the datatype: the ring
program uses MPI_INT but my test uses MPI_CHARACTER.
I tried changing from MPI_INT to MPI_CHARACTER in ring_c.c (and the
type of the variable "message" from int to char), and then ring_c.c
fails in the same way as my test code. And my code works if
changing from MPI_CHARACTER to MPI_INT.
So, it looks like the there is a bug that is triggered when using
MPI_CHARACTER, but it works with MPI_INT.
/ Elias
Quoting Ralph Castain <r...@open-mpi.org>:
Try running the "ring" program in our example directory and see if
that works
On Mar 16, 2014, at 4:26 PM, Elias Rudberg <elias.rudb...@it.uu.se> wrote:
Hello!
I would like to report a bug in Open MPI 1.7.4 when compiled with
--enable-mpi-thread-multiple.
The bug can be reproduced with the following test program
(mpi-send-recv.c):
===========================================
#include <mpi.h>
#include <stdio.h>
int main() {
MPI_Init(NULL, NULL);
int rank;
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
printf("Rank %d at start\n", rank);
if (rank)
MPI_Send(NULL, 0, MPI_CHARACTER, 0, 0, MPI_COMM_WORLD);
else
MPI_Recv(NULL, 0, MPI_CHARACTER, 1, 0, MPI_COMM_WORLD,
MPI_STATUS_IGNORE);
printf("Rank %d at end\n", rank);
MPI_Finalize();
return 0;
}
===========================================
With Open MPI 1.7.4 compiled with --enable-mpi-thread-multiple,
the test program above fails like this:
$ mpirun -np 2 ./a.out
Rank 0 at start
Rank 1 at start
[elias-p6-2022scm:2743] *** An error occurred in MPI_Recv
[elias-p6-2022scm:2743] *** reported by process
[140733606985729,140256452018176]
[elias-p6-2022scm:2743] *** on communicator MPI_COMM_WORLD
[elias-p6-2022scm:2743] *** MPI_ERR_TYPE: invalid datatype
[elias-p6-2022scm:2743] *** MPI_ERRORS_ARE_FATAL (processes in
this communicator will now abort,
[elias-p6-2022scm:2743] *** and potentially your MPI job)
Steps I use to reproduce this in Ubuntu:
(1) Download openmpi-1.7.4.tar.gz
(2) Configure like this:
./configure --enable-mpi-thread-multiple
(3) make
(4) Compile test program like this:
mpicc mpi-send-recv.c
(5) Run like this:
mpirun -np 2 ./a.out
This gives the error above.
Of course, in my actual application I will want to call
MPI_Init_thread with MPI_THREAD_MULTIPLE instead of just
MPI_Init, but that does not seem to matter for this error; the
same error comes regardless of the way I call
MPI_Init/MPI_Init_thread. So I just put MPI_Init in the test code
above to make it as short as possible.
Do you agree that this is a bug, or am I doing something wrong?
Any ideas for workarounds to make things work with
--enable-mpi-thread-multiple? (I do need threads, so skipping
--enable-mpi-thread-multiple is probably not an option for me.)
Best regards,
Elias
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