Visual Debugging Tools for Concurrent Models of Computation

1
Visual Debugging Tools for Concurrent Models of
Computation

• Elaine Cheong
• 15 May 2002
• EE290N Advanced Topics in System Theory

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Why Debugging?

• Software is complex.
• Concurrent software is even more complex.
• What if it the implementation does not behave as
  expected?
• Bugs, bugs, bugs

3
Outline

• Types of Debugging
• Debugging in Ptolemy II
• Future Work
• Conclusion

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Types of Debugging

• Event-based
• State-based

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Event-Based Debugging

• What is an event?
• Event order observation
• Event order tracking
• Event abstraction
• Filtering
• Clustering
• Interpretation
• Process abstraction

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State-Based Debugging

• Source-level debugging
• Consistent cuts
• Debugging
• Breakpoints
• Stepping
• Global step
• Step over
• Step in
• Global state predicates

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Probe Effects

• What is a probe?
• Code (or hardware) that generates debugging event
  records.
• Hook that provides access to the state of a
  process at runtime.
• Can mask or introduce new bugs.
• Permanent instrumentation for system monitoring.

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Ptolemy II

• A domain is an implementation of a model of
  computation.
• Ptolemy II domains are actor-oriented and
  concurrent, but are not threads.
• Visual interface.

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Debugging in Ptolemy II

• Demo!

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Conclusions

• Both event- and state-based debugging is possible
  in Ptolemy II.
• Future Work
• Additional domains
• Additional state information
• Predicates for breakpoints using the expression
  language.
• Generate trace diagrams.

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References

• Peter C. Bates. Debugging Heterogeneous
  Distributed Systems Using Event-Based Models of
  Behavior. ACM Transactions on Computer Systems,
  Vol. 13, No. 1, Feb 1995, pg 1-31.
• Kenneth J. Hines. Coordination-centric Debugging
  for Heterogeneous Distributed Embedded Systems.
  Ph.D. Dissertation. 2000.
• S. I. Hyder et al. A Unified Model for
  Concurrent Debugging. International Conference
  on Parallel Processing, 1993.
• Ronald A. Olsson et al. A Dataflow Approach to
  Event-Based Debugging. Software Practice and
  Experience, Vol. 21, No. 2, 1991, pg 209-230.
• M. Krish Ponamgi. Debugging Multi-Threaded
  Programs with MpD. IEEE Software, pg 37-43, May
  1991.
• Richard M. Stallman. GDB Manual The Gnu
  source-level debugger. Free Software Foundation,
  1987.

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Questions