13.5. Broadcast Communications

In this subsection, we will further improve the efficiency of our code by introducing two new MPI functions. In the process, we'll reduce the amount of code we have to work with.

13.5.1. Broadcast Functions

If you look back to the last solution, you'll notice that the parameters are sent individually to each process one at a time even though each process is receiving the same information. For example, if you are using 10 processes, while process 0 communicates with process 1, processes 2 through 10 are idle. While process 0 communicates with process 2, processes 3 through 10 are sill idle. And so on. This may not be a big problem with a half dozen processes, but if you are running on 1,000 machines, this can result in a lot of wasted time. Fortunately, MPI provides an alternative, MPI_Bcast.