Dynamic data decomposition in a message-passing environment

The performance of a data parallel program is critically dependent on the data decomposition that the programmer chooses at implementation time. This choice must take into account a combination of different factors such as the kind of the problem, the machine architecture and the data domain size. When these elements are known before execution, the programmer can adopt traditional message-passing languages and optimise performance by means of programs which are dependent on the chosen data decomposition. On the other hand, when the factors that determine the best decomposition are known at run-time only, adequate efficiency can be achieved by a code that dynamically adapts its computation/communication pattern to various decompositions. To assist the programmer in the implementation of a decomposition-independent code, we propose a new programming environment, namely PLUS. It provides the programmer with message-passing primitives that avoid the specification of a data decomposition during the implementation phase, and a run-time support that permits dynamic changes among regular decompositions without affecting the implemented program.