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

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."

CS 3500 L12pp - 3 This Is Pair Programming

CS 3500 L12pp - 4 This is NOT Pair Programming

CS 3500 L12pp - 5 Pair Programming Has Been Around For a LONG TIME! … 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.

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

CS 3500 L12pp - 7 Findings #1 - Quality

CS 3500 L12pp - 8 Findings #2 - Time

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

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

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

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%)

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

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

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

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

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

CS 3500 L12pp - 18 More Information l Bob Kessler l Laurie Williams l l