TAU Trace Measurement

TAU's measurement library treats events from different instrumentation layers in a uniform manner. TAU supports message communication events, timer entry and exit events, and user-defined events. Timer entry and exit events can apply to a group of statements as well as routines. User-defined events are specific to the application and can measure entry/exit actions as well as atomic actions. TAU can generate profiles by aggregating performance statistics such as exclusive and inclusive times spent in routines, number of calls, etc. These profiles are written to files when the application terminates. With the same instrumentation, TAU can generate event traces, which are time-ordered event logs. These logs contain fixed-size trace records. Each trace record is a tuple comprising of an event identifier, a timestamp, location information (node, thread) and event specific parameters. The trace records are periodically flushed to disk when private in-memory buffers overflow, or when the application executes a call to explicitly flush the buffers. TAU also writes event description files that map event identifiers to event properties (such as event names, group names, tags, and event parameter descriptions).