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Residual Communication

This is an important aspect of the proto-Cdyn layer. As indicated in the startup-phase discussion, the members of a process column initially share information about the groups of states and nonstates they will exchange during a residual computation. For residual communication, a reactive transmission mechanism is employed to avoid deadlocks.  Each process transmits its next group of states to the appropriate process and then looks for any receipt of state information. Along with the state values are indices that directly drive the destinations for these values. This index information is shared during the startup phase and allows the messages to drive the operation. Through nonblocking receives, this procedure avoids problems of transmission ordering. Regardless of the template structure, at most one send and receive is needed between any pair of column processes.

Guy Robinson
Wed Mar 1 10:19:35 EST 1995