MPI Communication Structure

Chapter5.tex

@@ -58,6 +58,7 @@ For determining which tasks should be handled by the root note, a few considerat
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 \TUsubsubsection{Communication Structure}
+The underlying communication structure for the tasking approach relies on a pseudo-ring structure. As seen in \ref{fig:node-alloc}, nodes n$_2$, n$_3$, and n$_4$ are derived from the previous task's greatest node rank. To keep the development abstract, a custom send function would check the world size before sending. If the rank of the node that would receive a message is greater than the world size and therefore does not exist, the rank would then be looped around and corrected. After the rank correction, the MPI Send function was then invoked with the proper node rank.
 
 \TUsubsubsection{Task 0}
 Task 0 is performed by the root node, and is a conditional task; it is not guaranteed to be executed at each pipeline iteration. Task 0 is only executed when the frontier is empty, but the database still holds unexplored states. This occurs when there are memory constraints, and database storage is performed during execution to offload the demand, as discussed in Section \ref{sec:db-stor}. After the completion of Task 0, the frontier has a state popped, and the root node sends the state to n$_1$. If the frontier is empty, the root node sends the finalize signal to all nodes.