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Subject: [OMPI devel] shmem_collect32 does not work with nlong == 0
From: Bert Wesarg (Bert.Wesarg_at_[hidden])
Date: 2014-05-10 08:46:58


I get a deadlock when using the shmem_collect32() routine and any of the
non-root PEs pass 0 as the number of elements. It looks like the
algorithm in _algorithm_central_collector() does use 0 as a special
value, and thus does not break out of the loop. This is observable with
1.8 and current trunk r31639. A small testcase is attached.

Btw, I'm pretty confident, that this Open SHMEM implementation does not
recognize global or static variables in shared libraries as symmetric
objects. It is probably wise to note this somewhere to the users.

Kind regards,
Bert Wesarg

#include <shmem.h>

main(int ac, char *av[])
     int *src, *dest;
     long *psync;

     int pes = _num_pes();
     int me = _my_pe();

     src = shmalloc(pes * sizeof(*src));
     for (int pe = 0; pe < pes; ++pe)
         src[pe] = me;
     dest = shmalloc(pes * sizeof(*dest));
     psync = shmalloc(_SHMEM_COLLECT_SYNC_SIZE * sizeof(*psync));
     for (int i = 0; i < _SHMEM_COLLECT_SYNC_SIZE; ++i)
         psync[i] = _SHMEM_SYNC_VALUE;

                     me == 0 ? 1 : 0,
                     0, 0, pes,


     return 0;

Dipl.-Inf. Bert Wesarg
wiss. Mitarbeiter
Technische Universität Dresden
Zentrum für Informationsdienste und Hochleistungsrechnen (ZIH)
01062 Dresden
Tel.: +49 (351) 463-42451
Fax: +49 (351) 463-37773
E-Mail: Bert.Wesarg_at_[hidden]