Dynamic Event Registration

For runtime trace reading and analysis, it is important to understand what takes place when TAU records performance events in traces. The first time an event takes place in a process, it registers its properties with the TAU measurement library. Each event has an identifier associated with it. These identifiers are generated dynamically at runtime as the application executes, allowing TAU to track only those events that take actually occur. This is in contrast to static schemes that must predefine all possible events that could possibly occur. The main issue here is how the event identifiers are determined. In a static scheme, event IDs are drawn from a pre-determined global space of IDs, which restricts the scope of performance measurement scenarios. In our more general and dynamic scheme, the event identifiers are generated on-the-fly, local to a context. Depending on the order in which events first occur, the IDs may be different for the same event (i.e., events with the same name) across contexts. When event streams are later merged, these local event identifiers are mapped to a global identifier based on the event name. The TAU trace merging operation is discussed in section 4.3.