MPI on Cougar for ASCI Red

Implementation of ANL/MSU MPICH on top of Puma portals

MPI Point-to-point communication built directly on top of portals with minimal support from system portal library.

MPI Collective functions on top of native Puma collective operations

For point-to-point communications, a two-level protocol is used in an attempt to decrease latency for short messages and increase bandwidth for longer messages. In this protocol, short messages are sent optimistically and buffered at the receiver. Should a matching receive not be posted, the message is stored in a dynamic heap and copied into the user buffer when a matching receive is posted. Long messages are also sent optimistically, but only a message header is buffered at the receiver when no matching receive is present. When a matching receive is eventually posted, the receiver pulls the message from the sender. If a matching receive is pre-posted, the message is deposited directly into the user buffer.

If you have any questions, email janus-help@sandia.gov

Updated: August 14, 2003
For information and feedback about these pages, please contact:
Robert K. Thomas -- rkthoma@sandia.gov

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