Safe Use of System Buffers

In some MPI programs, processes send large volumes of data with blocking sends before starting to receive messages. The MPI standard specifies that users must explicitly provide buffering in such cases, perhaps using MPI_Bsend calls. In practice, however, some users rely on the standard send routine (MPI_Send) to supply unlimited buffering. By default, Sun MPI prevents deadlock in such situations through general polling, which drains system buffers even when no receives have been posted by the user code.

For best performance on typical, safe programs, you can suppress general polling should by setting MPI_POLLALL:

% setenv MPI_POLLALL 0