Torsten,
2) Keith and Brian, could you please elaborate on the arguments against allowing multiple elements (count>1) in MPI_Get_accumulate? I remember there was some discussion about buffering and failures if one wanted to support it in hardware but I don't remember what the issues were. It seems like one could simply pipeline the hardware operations or just fall back to a software implementation if count is bigger than a certain threshold.
With pipelining, I assume atomicity is only per element? I do not see how you could realize anything else in hardware. I don't see any value in multi-element RMW if it is element-wise atomic. One could just as easily send multiple messages. What is the use case multi-element RMW anyways? I'm definitely going to need message-atomic put, but I'll do the portable i.e. MPI version with RMW-lock + put + RMW-unlock. Jeff -- Jeff Hammond Argonne Leadership Computing Facility [email protected] / (630) 252-5381 http://www.linkedin.com/in/jeffhammond