Section: New Results

Tag matching in constant time

Tag matching is the operation, inside an MPI library, of pairing a packet arriving from the network, with its corresponding receive request posted by the user. This operation is not straightforward given that matching criterions are the communicator, the source of the message, a user-supplied tag, and since there are wildcards for tag and source. State of the art algorithms are linear with the number of pending packets and requests, or don't support wildcards.

We proposed [17] an algorithm that is able perform the matching operation in constant time, in all cases, even with wildcard requests. We implemented the algorithm in our NewMadeleine communication library, and demonstrated it actually improves performance of Cholesky factorization with Chameleon running on top of StarPU .