Hi, I have one question about the array parameters (sendcounts, recvcounts, sdispls and rdispls) in nonblocking collectives such as MPI_IALLTOALLV. Are callers allowed to modify/destroy those arrays upon the return of the calls, or they must wait until after the MPI_WAIT call? I could not find the correct behavior defined in the latest proposal (nbc-proposal-rev-6.2.pdf) and do not remember having discussion on such. I think this issue is quite unique to nonblocking collective communication calls since arrays in other MPI nonblocking calls are arrays of MPI objects, for which the correct handling is well defined. So it needs to be clarified. Am I missing something? Thanks Bin Jia Communication Protocol Development Advanced Clustering Technology Team, IBM STG Poughkeepsie, NY 12601 Tel: 845-433-6301(T/L 293-)