On Wed, Feb 01, 2012 at 02:48:16PM -0600, Quincey Koziol wrote:
I would have to look up if this is the way the standard looks at it, but one possible way of reasoning about the non-blocking collectives is to consider them to be blocking from the time they are started up to the time they are completed by wait/test/...
In this case, the example reduces to having two threads doing a MPI_File_read_ordered on the same file handle.
It is perfectly valid to ask what happens in MPI 2.2 in this case.
Clearly, for the split collectives, doing this is /not/ legal as the standard explicitly prohibits having more than one split collective on the same file handle at the same time.
But really, somebody with better knowledge of the non-blocking collectives should answer what happens if two MPI_Iscan operations are executed on the same communicator.
Torsten? (CC'd) There are obviously no filehandles in NBC. The scan operations match in issue-order and the buffers specified have to be disjunct (as for any nonblocking communication in MPI). I.e., the two NBCs do not influence each other from a correctness perspective.
Torsten -- bash$ :(){ :|:&};: --------------------- http://www.unixer.de/ ----- Torsten Hoefler | Performance Modeling and Simulation Lead Blue Waters Directorate | University of Illinois (UIUC) 1205 W Clark Street | Urbana, IL, 61801 NCSA Building | +01 (217) 244-7736