MPI message
MPI message includes two parts—envelope and data. The envelope consists of identifying information including the source/destination, tag, and communicator, while data is the content to be delivered. The envelope and data include three parts, which can be represented by a ternary array:
- Envelope: Source/destination, ID, communication domain
- Data: Start address, count, datatype
The following screenshot illustrates this structure:
Figure 14.1 – Structure of the envelope and data
In addition to the source and destination, there are tags in the message envelope to allow the receiver to distinguish between two or more messages of the same type sent from the same sender to the same receiver, as shown in the following screenshot:
Figure 14.2 – The role of envelope tags in distinguishing between simultaneous messages
In the preceding figure, Message 2 with tag2 arrives without a matching receive...
