Monitoring and Debugging Message Passing Applications with MPVisualizer Ana Paula Cláudio, João Duarte Cunha, and Maria Beatriz Carmo – Thu. Geum-Seo Koo Operating System Lab.

ClCC00 2 MPVisualizer A tool for the monitoring and debugging of message passing applications The reexecution mechanism includes two phases: trace and replay The graphical interface space-time diagram – happened-before relation defined by Lamport The visualization engine the core of the tool

ClCC00 3 The Re-execution Mechanism In the trace phase stored in order to minimize the probe effect inserted in the standard libraries In the replay phase force the re-execution to respect the causal order of the communication events recorded

ClCC00 4 The Visualization Engine Kernel classes include the basic classes do not depend on the graphical environment manager, process, message, machine, spy, c_event and its subclass c_event & direct subclass considering that communication events to distinguish between receive execution and message consumption inheritance Graphical classes subclasses of the classes in the kernel classes depend on the graphical S/W polymorphism

ClCC00 5 Class Diagram

ClCC00 6 Graphical Interface Progression of the re-execution symbols: processes, messages, and communication events The bottom windows give information about a process and a message sending

ClCC00 7 Detection of Race Conditions Comprises two steps detection of pairs of receive events in the same process verification of the legitimacy of the potential race condition According to Netzer and Miller “Two messages race if either could have been accepted first by some receive, due to variations in message latencies or process scheduling” p1p1 p2p2 p3p3 receive-from-any send

ClCC00 8 Predicate Detection Detectable predicates communication events, beginning and ending of processes The RACE condition window

ClCC00 9 Similar Tools #1 p2d2 (Portable Parallel Distributed Debugger) a gdb based portable debugger for parallel and distributed programs  MAD (Monitoring and Debugging Environment)  to give the user an environment for all activities of the debugging task

ClCC00 10 Similar Tools #2 DDBG (Distributed Debugger) a debugging tool integrated in the parallel software environment  TotalView  a debugger for single and multi-process programs in C, C++ and Fortran

ClCC00 11 Similar Tools #3 pdbx and pedb based on the sequential debugger dbx Xmdb a debugger for C, C++ and FROTRAN programs in PVM XPVM provides animated views to monitor the execution of PVM P/G

ClCC00 12 Conclusions and Future Work Conclusions advantage of inheritance and polymorphism be adapted to different message passing environments and different graphical environments and easily re-programmed to detect specific predicates Future Work A major improvement in tool breakpoint mechanism Scalability aspects zoom mechanism