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Debugging an Operation

This session discusses debugging an operation using a failed proof of correctness as a guide. It covers topics such as implementing the operation, creating a testing harness, receiving unexpected output, and using genetic algorithms for code mutations.

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Debugging an Operation

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  1. Using a Failed Proof of Correctness as a Guide Debugging an Operation Joan Krone – Denison University Joseph Hollingsworth – Indiana University Southeast SIGCSE 2013 Special Session

  2. What Went Wrong? • Student implements an operation • Student creates a testing harness a small client program • Student runs the testing harness • Receives unexpected output • The operation doesn’t seem to do anything! SIGCSE 2013 Special Session

  3. Invert The outgoing Q equals the reverse of the incoming Q • #Q – incoming • Q – outgoing P_Queue is a preemptable queue • Has one additional operation – Inject SIGCSE 2013 Special Session

  4. String Theory Used for mathematically modeling a Queue •  - is the alphabet, e.g.,  = Z SIGCSE 2013 Special Session

  5. String Theory Used for mathematically modeling a Queue •  - is the alphabet, e.g.,  = Z • Example strings: • α = <4,22,3,17> string of 4 integers • β = < > empty string SIGCSE 2013 Special Session

  6. String Theory Used for mathematically modeling a Queue •  - is the alphabet, e.g.,  = Z • Example strings: • α = <4,22,3,17> string of 4 integers • β = < > empty string • Concatenation, Length, Reverse • <-5> o α o <101> = <-5,4,22,3,17,101> • |α| = 4 • Reverse(α) = <17,3,22,4> • Reverse(αo <101>) = <101,17,3,22,4> SIGCSE 2013 Special Session

  7. Testing Harness for Invert Output: q before Invert = <3,2,1> q after Invert = <3,2,1> SIGCSE 2013 Special Session

  8. How to Debug?I Could Try … • Using one of those genetic algorithms to make random mutations to my code … SIGCSE 2013 Special Session

  9. Or Maybe I Should … • Do that proof of correctness thingy that my professor showed us. SIGCSE 2013 Special Session

  10. Accessing theRESOLVE Web Interface SIGCSE 2013 Special Session

  11. Accessing Components SIGCSE 2013 Special Session

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