Structure of an Application

So far, we have seen a Diamond application as a network of tasks spread over a number of processors, possibly with more than one task per processor. These tasks communicate only through channels. If a task wishes to communicate with a task on another processor, the channel communications will result in the messages being transmitted across the inter-processor links.

Typically, the whole network is controlled by another processor, which we call the host. The host communicates directly with only one processor in the network, which we call the root. In fact, the application also includes a number of other parts. We shall look at these one by one.