...

Would you think the user would expect that having the same source and target buffer would cause the implementation to:

-allocate a buffer -perform a get into that buffer -wait for get completion -perform an atomic -wait for atomic completion -copy the data from the internal buffer to the user buffer

Why are you trying to it atomically? Get_accumulate is only element- wise atomic.

Er, atomic only in the sense that Get_accumulate implies... So, replace "atomic" with "put" above and you still have something ugly. Point is: you have to wait for the get of a segment to complete before you can do the put. You have to wait for the put of a segment to complete before you can copy the result of the get (otherwise your retransmits are going to cause you great fun). Keith