Extreme Pairing

December 14, 2010 Pivotal Labs

Given the recent interest and discussions around pair programming, I thought that now would be a good time to write up my experiences doing dual-computer, in-person pair programming with Mavenlink at Pivotal Labs. Pivotal Labs is all about pairing and every team here pairs full time. Our standard setup is to have two developers at each workstation, with two mice and keyboards. On Mavenlink, we recently upgraded our workstations and decided to keep the older model around to try out dual-computer pairing, which we’ve nicknamed “Extreme Pairing.”

One commonly-expressed frustration with pair programming is that of wasted time while doing especially rote programming, research, documentation reading, or printout debugging tasks. People read documentation at different speeds, or want to try different Google searches in parallel, for example. Generally, the benefits of pair programming greatly outweigh the downsides, and we pair full-time to decrease the risk of failing to pair when it would retrospectively have been of great value due to knowledge sharing or bug prevention. However, in an effort to minimize these inefficiencies, the Mavenlink team has been exploring dual-computer pairing.

What follows is not Pivotal’s standard pairing setup. Everyone on this team has years of pair-programming experience and we have each developed our own intuition for which corners can be cut and which cannot. The following is recommended for advanced pairs only — it can make experienced pairs more effective, but may be hazardous for newcomers to the pairing environment! We never “Extreme Pair” when conducting interviews and revert to a more traditional setup in that context.

Extreme Pairing

Each of our two pairing desks house a beefy i7 27-inch iMac and a slightly older 24-inch iMac, each with its own mouse and keyboard, and linked bidirectionally with Teleport. We sit centered around the larger iMac and use the second computer when we have separable tasks during pairing, such as research, running tests, or looking up documentation. We still do traditional pairing 90%+ of the time and focus on never falling into the traps of soloing: email checking, distractions, siloed knowledge, and untested code. Having the second computer has allowed us to split our focus when we can do so while still both maintaining understanding and ownership of everything that is going on. This is most effective and appropriate when:

  • tracking down bugs; we are both able to apply different tactics simultaneously while talking to each other. This allows us to divide and conquer, then rejoin when we’ve made progress in our understanding of the base problem.
  • looking at docs; we can both read at our own pace and synchronize afterwards.
  • the non-driving pair can support the driver by setting up the context for an experiment, running rake tasks, etc.
  • googling and researching
  • optimizing, one person can track down issues with Query Reviewer or Rack Bug while the other can identify the underlying problems in the source.
  • browser testing and CSS tweaking in multiple browsers. In particular, we have found running windows in Parallels on the non-primary machine a boon to speed and productivity on the primary machine.
  • capturing stories in Pivotal Tracker

More generally, any time a task requires focus on two different places at once, we split it up and assist each other. I think of this as synchronization in multi-threaded code – we split and rejoin on separable sub tasks, while both continuing to perform traditional pair programming when viewed from the scope of a story. We never work on separate stories and tasks that last longer then a minute or so. Smoothly moving from traditional pair programming to separately googling, debugging, or CSS tweaking keeps us agile and efficient while maintaining all of the very-real benefits that we find to exist with traditional pair programming,

Does this sound like fun? Mavenlink and Pivotal Labs are hiring!

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