Trace Reader Library

To make the trace data available for runtime analysis, we implemented the TAU trace reader library. It can parse binary merged or unmerged traces (and their respective event definition files) and provides this information to an analysis tool using a trace analysis API. This API employs a callback mechanism where the tool registers callback handlers for different events. The library parses the trace and event description files and notifies the tool of events that it is interested in, by invoking the appropriate handlers with event specific parameters. We currently support callbacks for finding the following:

• Clock period used in the trace
• Message send or receive events
• Mapping event identifiers to their state or event properties
• Defining a group identifier and associated group name
• Entering and leaving a state

Each of these callback routines have event specific parameters. For instance, a send event handler has source and destination process identifiers, the message length, and its tag as its parameters. Besides reading a group of records from the trace file, our API supports file management routines for opening, closing a trace file, for navigating the trace file by moving the location of the current file pointer to an absolute or relative event position. It supports both positive and negative event offsets. This allows the analysis tool to read, for instance, the last 10000 events from the tail of the event stream. The trace reader library is used by VNG to analyze the merged binary event stream generated by an application instrumented with TAU.