The Four Minute Mile

Sometimes these posts get off topic, sometimes in the direction of the art of computer programming, sometimes in the nature of the industry, and sometimes with pictures of the pets. This post is going to go off a bit into the subject of project management.

Randy and Tyler posted what was becoming clear (by the lack of an already existing beta): our estimated release date for X-Plane 10 was incorrect. Software project delays are pretty common, and often when a third party add-on is delayed, the community jumps to speculate about “what’s going on” inside the project and tries to infer whether the delay is an indication of serious problems.

I’d like to try to reframe the issue of delays in terms of an analogy. You ask me: how fast can you run a mile? I tell you “4 minutes and 15 seconds”. I then run a mile and you time me. My time: 6 minutes, 10 seconds.* What can we learn from this episode? I think we can learn two things:

• For a computer programmer, I am surprisingly fast – a six minute mile isn’t to be sneezed at when you spend your days sitting on your ass in front of a monitor drinking coffee.
• My ability to predict my own speed is not very good. I was pretty naive to think I could run a 4 minute mile – that’s what world class athletes run. My estimate was off by a fairly big error margin.

One thing we should not conclude is that because my mile time was 2 minutes slower than estimated, that I am a slow runner. The estimate sets up an expectation, but if the estimate is wrong, it’s not a useful metric of efficiency.

The same applies to X-Plane; we missed our original projected ship date because the estimation of when we would be done was not a very good estimate. This isn’t good for a few reasons:

• It creates uncertainty for third parties as to when a platform will change.
• It makes it difficult for marketing to properly plan a roll-out.
• It makes it difficult to balance the value of more features vs. an earlier release date (since we don’t know how much “time” we are trading for “features” if the time estimates are wrong).

But the delay is not at all a black mark for our team – on the contrary, they’re working their asses off and creating some really great work.

When looking at a project that will be delayed (because the original schedule was wrong) there’s a few things you can do:

1. Add more people. This is quite often the wrong thing to do – please read the Mythical Man Month to understand why. Once your team is the right size, adding more warm bodies usually makes schedule delays worse and hurts efficiency.
2. Remove features. This is the only real way to bring in a ship date.
3. Move the date back.

When Austin and I were working on X-Plane 8, we hit a similar scheduling problem – what we had set out to do was going to take a lot longer than we thought. (Like X-Plane 10, we had just doubled the team size and begun a project that involved massive rewrites, which made it hard to ship until the work was fully complete. Sound familiar?) The difference? With X-Plane 8 we had contracted to ship with an external distributor for Thanksgiving, so we had to go for item 2 – we cut scope. What we cut was the world – that is, we shipped new global scenery only for the US, and the existing ENVs for the rest of the world. We also had to ship the artwork we had on hand, despite being unhappy with its quality. We didn’t finish the rest of the world and graphics we were happy with for another 11 months.

Option 2, cutting scope is painful and hard. Sometimes it is the right thing to do. In the case of X-Plane, however, we have the luxury to move the date back. With that in mind, we’re trying as hard as we can to keep feature-creep minimal and finish what we’ve already bit off, so we can get the release done and out the door.

* My mile time is not 6 minutes, 10 seconds…I would be astounded, and quite possibly in the ER if I could run that fast for any sustained amount of time.

About Ben Supnik

Ben is a software engineer who works on X-Plane; he spends most of his days drinking coffee and swearing at the computer -- sometimes at the same time.

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