As I said in my previous email it is legal to use such an overlapping datatype for send operations. Thus, the datatype engine cannot prevent one from creating them.
We had some degree of overlap detection at some point in the past, but the algorithm is quadratic in time and memory with the number of datatype entries, so the cost was prohibitive. George. On Wed, Jan 21, 2015 at 9:43 AM, Jeff Squyres (jsquyres) <jsquy...@cisco.com > wrote: > On Jan 20, 2015, at 10:10 PM, George Bosilca <bosi...@icl.utk.edu> wrote: > > > > Receiving with such a datatype is illegal in MPI (sending is allowed as > the buffer is supposed read only during the operation). In fact having any > datatype that span over the same memory region twice is illegal to be used > for any receive operations. The reason is simple, an MPI implementation can > move the data in any order it wants, and as MPI guaranteed only the FIFO > ordering of the matching such a datatype will break the determinism of the > application. > > George: does the DDT engine check for this kind of condition? Shouldn't > it refuse the generate a datatype like this? > > -- > Jeff Squyres > jsquy...@cisco.com > For corporate legal information go to: > http://www.cisco.com/web/about/doing_business/legal/cri/ > > _______________________________________________ > devel mailing list > de...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > Link to this post: > http://www.open-mpi.org/community/lists/devel/2015/01/16810.php >
