I agree that in practice the best practice would be to use Win_shared_query.
Still I am confused by this part in the documentation: "The allocated memory is contiguous across process ranks unless the info key alloc_shared_noncontig is specified. Contiguous across process ranks means that the first address in the memory segment of process i is consecutive with the last address in the memory segment of process i - 1. This may enable the user to calculate remote address offsets with local information only." Isn't this an encouragement to use the pointer of Win_allocate_shared directly? Peter ----- Original Message ----- > I don't know about bulletproof, but Win_shared_query is the *only* valid way > to get the addresses of memory in other processes associated with a window. > The default for Win_allocate_shared is contiguous memory, but it can and > likely will be mapped differently into each process, in which case only > relative offsets are transferrable. > Jeff > On Wed, Feb 10, 2016 at 4:19 AM, Gilles Gouaillardet < > gilles.gouaillar...@gmail.com > wrote: > > Peter, > > > The bulletproof way is to use MPI_Win_shared_query after > > MPI_Win_allocate_shared. > > > I do not know if current behavior is a bug or a feature... > > > Cheers, > > > Gilles > > > On Wednesday, February 10, 2016, Peter Wind < peter.w...@met.no > wrote: > > > > Hi, > > > > > > Under fortran, MPI_Win_allocate_shared is called with a window size of > > > zero > > > for some processes. > > > > > > The output pointer is then not valid for these processes (null pointer). > > > > > > Did I understood this wrongly? shouldn't the pointers be contiguous, so > > > that > > > for a zero sized window, the pointer should point to the start of the > > > segment of the next rank? > > > > > > The documentation explicitly specifies "size = 0 is valid". > > > > > > Attached a small code, where rank=0 allocate a window of size zero. All > > > the > > > other ranks get valid pointers, except rank 0. > > > > > > Best regards, > > > > > > Peter > > > > > > _______________________________________________ > > > > > > users mailing list > > > > > > us...@open-mpi.org > > > > > > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > > > > > > Link to this post: > > > http://www.open-mpi.org/community/lists/users/2016/02/28485.php > > > > > _______________________________________________ > > > users mailing list > > > us...@open-mpi.org > > > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > > > Link to this post: > > http://www.open-mpi.org/community/lists/users/2016/02/28493.php > > -- > Jeff Hammond > jeff.scie...@gmail.com > http://jeffhammond.github.io/ > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/02/28496.php
