Understanding and debugging concurrent programs through visualisation
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School of Science |
Doctoral thesis (article-based)
| Defence date: 2012-03-16
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Author
Date
2012
Major/Subject
Mcode
Degree programme
Language
en
Pages
180
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 24/2012
Abstract
In this thesis, the development and evaluation of a visualisation system intended to support students in understanding and debugging concurrent programs is presented. The first phase of development consisted of examining how students understand and develop concurrent programs through phenomenographic research. The resulting outcome spaces included the students' understandings of tuple spaces, the purpose of a programming assignment and what developing, debugging and testing a concurrent program involves. The outcome spaces included categories ranging from simple understandings containing only what is necessary to complete the assignments to understandings that placed the program in a larger context beyond the assignment. These outcome spaces were used in a classification of defects in students' concurrent programs. The defects found in the students' programs were classified by the underlying human error and by the type of program failure the defect causes. This analysis of defects was used to determine appropriate measures to support students in avoiding such defects. Many of the students' defects were related to misunderstanding the goals of the assignment, so they were rewritten to clarify the goals. To give the students a more concrete demonstration of the situations their programs had to deal with, test packages were provided to them. Many of the students' defects were related to incorrect use of concurrency. To help students understand and correct these defects and learn from their mistakes, the visualisation system Atropos was developed. Atropos is intended to help students understand concurrent program behaviour in Java. Atropos supports backward debugging of concurrent Java programs through interactive exploration of a dynamic dependence graph. A solution for replay and dynamic dependence analysis of concurrent Java programs that may include data races was devised. Atropos was evaluated through a mixed-methods analysis of the behaviour of pairs of students using Atropos to debug concurrent programs. The results include a description of the ways in which students successfully made use of Atropos and suggestions for how it could be improved to better support their debugging approaches. While students appear to understand the dependence graph representation and how to apply it in debugging, they need more support from Atropos for eliding the implementation of data structures in order to examine their use.I denna avhandling presenteras utvecklingen och utvärderingen av ett visualiseringssystem som skapats för att hjälpa studenter förstå och avlusa jämlöpande program. I den första utvecklingsfasen undersöktes genom en fenomenografisk undersökning hur studenter uppfattar och utvecklar jämlöpande program. Utfallsrummen från denna undersökning handlade om hur studenter uppfattar tupelrymder, avsikten med ett övningsarbete i programmering och vad som ingår i utvecklandet, avlusandet och testandet av ett jämlöpande program. Utfallsrummen innehöll beskrivningskategorier från enkla uppfattningar som bara omfattar det som krävs för att utföra övningarna till uppfattningar som satt programmet i ett sammanhang som sträcker sig bortom övningen. Utfallsrummen användes för att klassificera buggarna i studenternas jämlöpande program. Buggarna klassificerades enligt det bakomliggande mänskliga felet och enligt det felaktiga uppförandet i programmet buggen ger upphov till. Denna analys av buggarna användes för att finna lämpliga medel för att hjälpa studenter undvika att skapa dylika buggar. Många av buggarna kom från att studenterna missförstått övningsarbetenas mål, så de skrevs om för att förtydliga målen. Studenterna gavs testpaket som gav dem en mer konkret demonstration av övningsarbetenas mål. Många av studenternas buggar var kopplade till felaktigheter i samverkan mellan exekveringstrådar. För att hjälpa studenter förstå och korrigera dessa buggar och lära sig från sina misstag utvecklades visualiseringssystemet Atropos. Atropos är tänkt att hjälpa studenter förstå hur jämlöpande program i Java uppför sig. Atropos stöder baklänges avlusning av jämlöpande Java-program genom interaktiv utforskning av en dynamisk beroendegraf. En lösning skapades för återuppspelning och dynamisk beroendeanalys av jämlöpande Java-program som kan innehålla datatävlingssituationer. Atropos utvärderades genom en analys av hur par av studenter använde Atropos för att avlusa jämlöpande program. Analysen gjordes med kvalitativa och kvantitativa metoder. Utvärderingens resultat omfattar bland annat en beskrivning av hur studenterna utnyttjade Atropos och förslag för hur Atropos bättre kunde stöda deras sätt att avlusa. Fastän studenterna verkar förstå beroendegrafsrepresentationen och hur den kan utnyttjas i avlusning, borde Atropos ha bättre stöd för att dölja implementationen av datastrukturer då användningen av dem undersöks.Description
Supervising professor
Malmi, Lauri, ProfessorThesis advisor
Ben-Ari, Mordechai, Associate ProfessorKeywords
software visualisation, concurrent programming, dynamic dependence analysis, computer science education, phenomenography, programvisualisering, jämlöpande programmering, dynamisk beroendeanalys, datadidaktik, fenomenografi
Other note
Parts
- [Publication 1]: Jan Lönnberg and Anders Berglund. Students' understandings of concurrent programming. In Proceedings of the Seventh Baltic Sea Conference on Computing Education Research (Koli Calling 2007), pp 77-86, Koli, Finland, April 2008. © 2008 Australian Computer Society. By permission.
- [Publication 2]: Jan Lönnberg, Anders Berglund and Lauri Malmi. How students develop concurrent programs. In Proceedings of the Eleventh Australasian Computing Education Conference (ACE2009), pp 129-138, Wellington, New Zealand, January 2009. © 2009 Australian Computer Society. By permission.
- [Publication 3]: Jan Lönnberg. Defects in Concurrent Programming Assignments. In Proceedings of the Ninth Koli Calling International Conference on Computing Education Research (Koli Calling 2009), pp 11-20, Koli, Finland, November 2009. © 2009 Association for Computing Machinery (ACM). By permission.
- [Publication 4]: Jan Lönnberg, Mordechai Ben-Ari and Lauri Malmi. Java Replay for Dependence-based Debugging. In Proceedings of PADTAD IX - Workshop on Parallel and Distributed Systems: Testing, Analysis, and Debugging, pp 15-25, Toronto, Ontario, Canada, July 2011. © 2011 Association for Computing Machinery (ACM). By permission.
- [Publication 5]: Jan Lönnberg, Mordechai Ben-Ari and Lauri Malmi. Visualising Concurrent Programs with Dynamic Dependence Graphs. In Proceedings of 6th IEEE International Workshop on Visualizing Software for Understanding and Analysis (VISSOFT 2011), 4 pp, Williamsburg, Virginia, USA, September 2011. © 2011 Institute of Electrical and Electronics Engineers (IEEE). By permission.
- [Publication 6]: Jan Lönnberg, Lauri Malmi and Mordechai Ben-Ari. Evaluating a Visualisation of the Execution of a Concurrent Program. Proceedings of the Eleventh Koli Calling International Conference on Computing Education Research, pp 39-48, Koli, Finland, November 2011. © 2011 Association for Computing Machinery (ACM). By permission.