Hi all, Christof has found a potential problem in the API design that I think is worth discussing and (at least IMHO) worth changing: The current design returns the "count" of a variable, i.e., how many data elements are used to return or set the data, during the Get_info calls. For some variables, though, it may return information in multiple elements, e.g., once for each rank. The number of these elements, in this case, would depend on the MPI object we are binding the variable to and hence is not known until we allocate the matching handle. Examples for these kind of variables are eager limits that can be set on individual rank pairs or number of packets received or sent, again on individual communication pairs. In both cases the variable would be bound to / associated with a Comm object. The only way to support this in the current interface proposal is to return a count that is the biggest possible. In the example that would be the size of MPI_COMM_WORLD, which wouldn't scale. One (easy) way to solve this (and the credit for this goes to Christof) is to move returning the count from the Get_info calls to the Handle_allocate calls. This way, the count could be set based on the MPI object we are associating the variable with. Anybody see any problems with this change? Note, that valid implementations can still use scalar variables only by always return one for each allocated handle. Comments? Thanks, Martin ________________________________________________________________________ Martin Schulz, [email protected], http://people.llnl.gov/schulzm CASC @ Lawrence Livermore National Laboratory, Livermore, USA