Visualisation/explanations of different MPI send types

[steve-crouch]

Episode: Communicating Data in MPI

One learner found it hard to visualise the difference between MPI send types (MPI_Ssend, MPI-Bsend). Possible fixes:

• Perhaps a diagram could be added to the material to make the differences clearer, and/or
• An analogy added, e.g. SSend is like a phone call, Bsend a letter/email and Rsend is like a position update with air traffic control or something?
• We should also explain how Bsend is async but still a blocking function. The function won’t return until the data has been copied and safe to modify again. It’s blocking because MPI_Ibsend would return before it finished copying the data. Suggestion: perhaps also include (brief) use cases for when each is useful