7.1.1 Command Transfer and Communication

The processes that are involved in an ANSYS FLUENT session running in parallel are defined by Cortex, a host process, and a set of n compute node processes (referred to as compute nodes), with compute nodes being labeled from 0 to n-1 (Figure  7.1.4). The host receives commands from Cortex and passes commands to compute node-0. Compute node-0, in turn, sends commands to the other compute nodes. All compute nodes (except 0) receive commands from compute node-0. Before the compute nodes pass messages to the host (via compute node-0), they synchronize with each other. Figure  7.1.4 shows the relationship of processes in parallel ANSYS FLUENT.

Each compute node is "virtually'' connected to every other compute node and relies on its "communicator'' to perform such functions as sending and receiving arrays, synchronizing, performing global reductions (such as summations over all cells), and establishing machine connectivity. An ANSYS FLUENT communicator is a message-passing library . For example, it could be a vendor implementation of the Message Passing Interface (MPI) standard, as depicted in Figure  7.1.4.

All of the parallel ANSYS FLUENT processes (as well as the serial process) are identified by a unique integer ID. The host process is assigned the ID node_host(=999999). The host collects messages from compute node-0 and performs operation (such as printing, displaying messages, and writing to a file) on all of the data, in the same way as the serial solver. (Figure  7.1.5)

Figure 7.1.4: Parallel ANSYS FLUENT Architecture

Figure 7.1.5: Example of Command Transfer in Parallel ANSYS FLUENT