1. CS 3500 L12pp - 1 The Benefits of Pair Programming Robert Kessler School of Computing University of Utah Special thanks to Laurie Williams North Carolina State University

2. CS 3500 L12pp - 2 What Is Pair Programming? "Pair programming is a simple, straightforward concept. Two programmers work side-by-side at one computer, continuously collaborating on the same design, algorithm, code, and test. It allows two people to produce a higher quality of code than that produced by the summation of their solitary efforts."

3. CS 3500 L12pp - 3 This Is Pair Programming

4. CS 3500 L12pp - 4 This is NOT Pair Programming

5. CS 3500 L12pp - 5 Pair Programming Has Been Around For a LONG TIME!...19451953 …199719981999200020012002 John von Neumann, recognized his own inadequacies and continuously asked others to review his work. Fred Brooks and many others are pair programming, though they don’t know there is a name for it.

6. CS 3500 L12pp - 6 Does Pair Programming Really Work? l Empirical study by Laurie Williams at the university of Utah l Practice: Summer 1999 – 20 students (sophomore/junior) »All worked collaboratively – Generated more anecdotal/qualitative evidence l Solo vs. pair: Fall 1999 – 41 students (junior/senior) »28 worked collaboratively »13 worked individually – Software development process was controlled »The only experimental variable: pair-programming – Quantitative: time, quality, enjoyment, confidence

7. CS 3500 L12pp - 7 Findings #1 - Quality

8. CS 3500 L12pp - 8 Findings #2 - Time

9. CS 3500 L12pp - 9 Findings #3 and #4 – Enjoyment and Confidence

10. CS 3500 L12pp - 10 How Does This Work? l Pair-Pressure – Keep each other on task and focused – Don’t want to let partner down – “Embarrassed” to not follow the prescribed process – Parkinson’s law “work expands to fill all available time.” l Pair-Think – Distributed cognition: “searching through larger spaces of alternatives” »Have shared goals and plans »Bring different prior experiences to the task »Different access to task relevant information »Must negotiate a common shared of action l Pair-Relaying – Each, in turn, contributes to the best of their knowledge and ability – Then, sit back and think while their partner fights on

11. CS 3500 L12pp - 11 How Does This Work (Part Two)? l Pair-Reviews – Continuous design and code reviews – Ultimate in defect removal efficiency – Removes programmers distaste for reviews »80% of all (solo) programmers don’t do them regularly or at all l Debug by describing – Tell it to the Furby l Pair-Learning – Continuous reviews  learn from partners techniques, knowledge of language, domain, etc. – “Between the two of us, we knew it or could figure it out” – Apprenticeship – Defect prevention always more efficient than defect removal

12. CS 3500 L12pp - 12 Research Findings to Date - 1 l Strong anecdotal evidence from industry – “We can produce near defect-free code in less than half the time.” l Empirical study – Pairs produced higher quality code »15% less defects (difference statistically significant) »Observed – pairs produced smaller (LOC) programs – Pairs completed their tasks in about half the time »58% of elapsed time (difference NOT statistically significant) – Most programmers reluctantly embark on pair programming »Pairs enjoy their work more (92%) »Pairs feel more confident in their work products (96%)

13. CS 3500 L12pp - 13 Research Findings - 2 l Several educational studies underway – University of California, Santa Cruz; North Carolina State University – What about pair learning? »Anecdotal says that it works well – What are the long-term issues? »If you learn as a pair, can you work as a solo? l Distributed pair programming studies underway – North Carolina State University; University of North Carolina-Chapel Hill – Early results: distributed pair programming is viable – My experience: »Need to meet and know your pair »Need a good tool like VNC and telephone »Video not important

14. CS 3500 L12pp - 14 Issues: Workplace Layout Bad Better Best

15. CS 3500 L12pp - 15 Issues: Partner Picking Principles Expert paired with an Expert Expert paired with a Novice Novices paired togetherProfessional Driver ProblemCulture

16. CS 3500 L12pp - 16 Issues: Pair Rotation l Ease staff training and transition l Knowledge management/Reduced product risk l Enhanced team building

17. CS 3500 L12pp - 17 Expected Benefits of Pair Programming l Higher product quality l Improved cycle time l Enhanced learning l Pair rotation – Ease staff training and transition – Knowledge management/reduced product risk – Enhanced team building l Increased programmer satisfaction

18. CS 3500 L12pp - 18 More Information l Bob Kessler 801-581-4653 kessler@cs.utah.edu kessler@cs.utah.edu l Laurie Williams 919-513-4151 williams@csc.ncsu.edu williams@csc.ncsu.edu l http://pairprogramming.com l http://collaboration.csc.ncsu.edu/laurie