I have a further question to MPI_NO_OP and MPI_{R}Get_accumulate. I assume that origin_count is not significant for MPI_NO_OP (such as origin_datatype)

Like origin_addr, origin_count and origin_datatype should be ignored when MPI_NO_OP is used. I'm not sure that the text needs to be changed for this though. Pavan said that there is some text that asserts that buffers (i.e. pointers) be valid (i.e. not NULL) unless otherwise stipulated. Is there text to the same effect for count and datatype? If one uses count=0 in MPI_SEND, does the datatype have to be valid? If not, then we can ignore that argument at least. Since we don't have precedent for MPI_NO_OP, it seems that the notion that count can be ignored is implicitly obvious but nonetheless should be stated (or we could require count=0 for MPI_NO_OP...).

Which count variable defines the number of basic elements to be returned ? (result_count, result_type) or (target_count, target_type) ?

result_addr is the buffer that is written at the origin so I believe the answer is (result_count, result_type).

Should an error code be returned if the other number is too small ?

MPI-3 11.3.2 (MPI_GET_ ends with "The target buffer must be contained within the target window or within attached memory in a dynamic window, and the copied data must fit, without truncation, in the origin buffer." MPI-3 11.3.4 (MPI_ACCUMULATE) says something similar. I would contend that the same behavior applies to MPI_(R)GET_ACCUMULATE, but it might be appropriate to add text to this effect, just to be clear. We need to say slightly more than for MPI_GET though, because there are three (buffer, count, datatype) that need to be compatible. If we combine the restrictions for GET and ACCUMULATE, result_size<=target_size and origin_size<=target_size - size is derived from (count, datatype) - but I don't know that there has to be any restriction relating result_size and origin_size that isn't included in the former. Best, Jeff -- Jeff Hammond Argonne Leadership Computing Facility University of Chicago Computation Institute [email protected] / (630) 252-5381 http://www.linkedin.com/in/jeffhammond https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond