SBT is portable library and tool for on-line debugging and performance monitoring of shared-memory parallel programs using the single-program-multiple-data (SPMD) model of parallelism. SPMD programs often use barriers to synchronize threads of execution and to delimit the start and end of different phases of computation. Through its useful barrier constructs, dynamic performance warnings, and integration with hardware event counter libraries, SBT helps programmers localize deadlocks and performance bottlenecks in their parallel programs.

To demonstrate SBT?s applicability and usefulness, we present a simple, case study performance analysis using three programs from the SPLASH-2 suite. In addition, we quantify the overhead incurred by the programs when they are monitored with SBT, and conclude that the cost of the instrumentation is negligible.