| 5 | 5 | The MPI Library uses this principle to control the execution of a distributed program. Blocking function calls are used to prevent individual processors from resuming execution until the other processors are all caught up with them. For instance, a call to {{{MPI_Recv()}}} blocks until the processor has received the requested data. Once the data is received, {{{MPI_Recv()}}} returns and the calling process can resume executing. Some of the sending calls can block as well; {{{MPI_Ssend()}}}, for instance, blocks until the buffer on the sender is cleared and the receiver has started to receive the message. The blocking MPI functions can be used to keep the processors used in {{{mpibear}}} very tightly synchronized. |
