Parallel Simulation
problem — we have to select n events (assumed n processors in the parallel computer) to be executed and ensure that there is no causality errors.
Fundamental dilemma of PDES
- The ordering in which computation must be executed is relative to each other. This is in general quite complex and highly data dependent.
- How to decide whether n events can be executed concurrently? How do we know whether or not events affect each other without actually performing the simulation?
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Two categories of PDES mechanisms:
(a) conservative approach : avoid causality errors from occurring. Basic problem is to determine when it is safe to process an event.
(b) optimistic approach : causality errors are detected and a rollback mechanism is invoked to recover.