The MPI standard clearly states (in 8.7.1 Allowing User Functions at
Process Termination) that the mechanism you describe is only allowed on
MPI_COMM_SELF. The most relevant part starts at line 14.
George.
On Tue, Aug 26, 2014 at 11:20 AM, Lisandro Dalcin <dalc...@gmail.com> wrote:
> Another issue while testing 1.8.2 (./configure --enable-debug
> --enable-mem-debug).
>
> Please look at the following code. I'm duplicating COMM_WORLD and
> composing the dupe on it. The attribute free function is written to
> Comm_free the duped comm and deallocate memory. However, the run fails
> with the error you can see at the end.
>
> IMHO, this is a bug. This way of managing duplicated communicator
> contexts is quite common in parallel libraries. Moreover, In the MPI 3
> standard, page 364, lines 11 and 12, it says:
> """
> For example, MPI is “active” in callback functions that are invoked
> during MPI_FINALIZE.
> """
>
> Interestingly, if I replace WORLD -> SELF in the code below, I do not
> get the error.
>
> $ cat finalize.c
> #include <stdlib.h>
> #include <mpi.h>
>
> static int free_comm(MPI_Comm comm, int k, void *v, void *xs)
> {
> MPI_Comm_free((MPI_Comm *)v);
> free(v);
> return MPI_SUCCESS;
> }
>
>
> int main(int argc, char *argv[])
> {
> int keyval;
> MPI_Comm base,*comm;
> MPI_Init(&argc, &argv);
>
> MPI_Comm_create_keyval(MPI_COMM_NULL_COPY_FN, free_comm, &keyval, NULL);
>
> base = MPI_COMM_WORLD;
> comm = (MPI_Comm *)malloc(sizeof(MPI_Comm));
> MPI_Comm_dup(base, comm);
> MPI_Comm_set_attr(base, keyval, comm);
>
> MPI_Finalize();
> return 0;
> }
>
> $ mpicc finalize.c
> $ ./a.out
> *** The MPI_Comm_free() function was called after MPI_FINALIZE was invoked.
> *** This is disallowed by the MPI standard.
> *** Your MPI job will now abort.
> [kw2060:14603] Local abort after MPI_FINALIZE completed successfully;
> not able to aggregate error messages, and not able to guarantee that
> all other processes were killed!
>
>
> --
> Lisandro Dalcin
> ============
> Research Scientist
> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
> Numerical Porous Media Center (NumPor)
> King Abdullah University of Science and Technology (KAUST)
> http://numpor.kaust.edu.sa/
>
> 4700 King Abdullah University of Science and Technology
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