gave solutions that assumed a system fast enough to eliminate race conditions. Though incorrect, they provide a starting point for understanding atomic operations and the interleaving of instructions.

conclusion

In both their correct and incorrect preconceptions, the 66 students in our 2006 study apparently began their first computing course with essentially the same level of intuition as they began their first course involving concurrency. This similarity suggests students do not gain a deeper understanding of concurrency as they advance through the curriculum. As we have no data indicating that taking nonconcurrency courses provides skills that help one learn concurren-cy-related material more quickly, it may be there is no advantage to delaying the introduction of concurrency. Given the prevalence of concurrency and its increasing relevance at all levels and applications of CS, we suggest it may be wise to include concurrency earlier in the curriculum.

No matter which course introduces concurrency, the problem and student-proposed solutions in our study suggest ways to leverage student preconceptions. For example, instructors could conduct an exercise like this and choose student-generat-ed solutions for further discussion to explicitly address common errors. In particular, they could:

˲ ˲ Emphasize the real-world nature of the problem, pointing out related concurrency problems;

˲ ˲ Demonstrate that race conditions come up even in “fast” systems;

˲ ˲ Use responses that pass the buck (appearing to solve the concurrency problem by moving it to another operation without actually solving it) to help discuss the notion of atomic operations;

˲ ˲ Use a centralized solution to discuss interleaving instructions and pipelining technique; and

˲ ˲ Use responses that do not scale well to discuss scaling.

Here, we’ve addressed a rich set of
student responses that represent a
starting point for asking students to
critique proposed solutions, empha-
sizing concepts we know are at the
edge of their preconceptions. All such
concepts could be discussed early or
at least introduced in CS1.

acknowledgments

This material is based in part on work supported by the National Science Foundation under grants DUE-0736343, DUE-0736700, DUE- 0736572, DUE-0736738, DUE- 0736859, and DUE-0736958. Any opinions, findings, conclusions, or recommendations expressed here are those of the authors and do not necessarily reflect the views of the NSF. We thank the many students who responded to the questions used in this and our other studies; Sally Fincher, Josh Tenenberg, and the NSF (through grant DUE-0243242) who provided us with workspace at the SIGCSE conferences in 2006 and 2007; Renee McCauley, Sara Miner More, and Suzanne Westbrook for help with fall 2006 data collection and others who collected data for us in other commonsense projects; and the anonymous reviewers for their comments and suggestions. An earlier description of the study, with expanded analysis and discussion, is in the Proceedings of the Third International Computer Science Education Research Workshop. 9

 

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Gary Lewandowski ( [e-mail]) is a professor in and chair of the Department of Mathematics and Computer science at Xavier university, Cincinnati, oh.

Dennis J. Bouvier ( [e-mail]) is an associate professor in the Department of Computer science at southern Illinois university, edwardsville, Il.

Tzu-Yi Chen ( [e-mail]) is an associate professor in and chair of the Department of Computer science at Pomona College, Claremont, CA.

Robert McCartney ( [e-mail]) is an associate professor in the Department of Computer science and engineering at the university of Connecticut, storrs, CT.

Kate Sanders ( [e-mail]) is a professor in the Department of Math and Computer science at Rhode Island College, Providence, RI.

Beth Simon ( [e-mail]) is a lecturer with potential for security of employment in the Department of Computer science and engineering at the university of California, san Diego.

Tammy VanDeGrift ( [e-mail]) is an assistant professor in the Department of electrical engineering and Computer science at the university of Portland, Portland, o R.