Beltzner’s moving on.
When someone leaves the Mozilla Corp, it’s tradition for them to send a note to our global alias saying so. Mike sent his late last week, and this was my reply.
February, 2011
13
Feb 11
1 Year Old
“Da.”
It’s assertive, when I come in the door after work. A statement of fact. “Da has arrived, Mother, in case you were wondering.” And then you squeal, and crawl down off the couch backwards like we taught you, and you crawl over to the gate by the front door and reach up for me to pick you up. And then you remind me where every light in the house is by pointing to them. “Teh.” (pointing) “Teh.”
6 months ago you couldn’t crawl, now you’re starting to walk. 6 months ago you couldn’t talk, now you’re babbling constantly and have 4 or 5 words that are consistent and recognizable, even if they aren’t quite English. 6 months ago you were a baby and now… you’re not.
A lot can happen in 6 months, and a lot has. A lot of firsts, too. Your first tooth, first flight, first foreign country, first beer. Yeah, that’s right, beer. Why? Because you won’t tolerate not having any. Every food that Mommy and Daddy eat, you want; and you’re fearless. Olives, pickles, pizza, steak. You are fearless, in everything, and it scares the crap out of me.
Parents think stupid things, Lily. You’re fascinated with light, will you be a photographer? You love books, will that last, will you read everything you can get your hands on, like Daddy does? You love food now, does that mean you’ll be a foodie, or that you’ll end up flipping a switch and getting really picky? We try to predict the future from the scraps of information we have, because you so constantly surprise and amaze us; we’re desperate for some ability to understand what the future will be like. It’s exciting and scary and foggy and incredible. I don’t want to rush things, but I can’t wait for you to start talking more, because I see the things going on in your head and I want to know all about them.
I asked Grandma when it stops. When each week stops feeling like there’s a brand new kid in the house. Grandma said, “it stops?”
When I write the next one of these, you’ll be 18 months old and, for all I know, you’ll be in college. Go easy on me, Lily. Gently. I love you more than anything in the world, little girl, but it’s all I can do just to keep up.
Love,
Daddy
2
Feb 11
Vacuums and You (or, Estimating Like an Astronaut)
I’m going to teach you a surprisingly effective trick for estimating better, but first I need to talk about dressing up vacuum cleaners.
Ze Frank is a pretty creative guy, but what makes him really interesting to me is his ability to make other people creative. It’s what he does. He catalyzes creativity, frequently among those who don’t consider themselves creative. And when he talks about how he does it, he talks about the value of constraint.
Asked to go and “be creative,” he notes, most people shut down. So, instead, he asks for something more specific. He asked them to make a whole earth sandwich; they made a few. He asked people to send in pictures of vacuum cleaners dressed as people. He got 215. Constraining people, forcing them to solve a smaller problem, made them better at it.
Creativity isn’t the only thing that benefits from constraint. Asking engineers (or, really, anyone) for “an estimate” is basically akin to asking them to “be creative.” They know what examples of the thing in question look like, they understand that it’s a reasonable request, they just don’t actually know how to get there from here, much less how to be accurate about it.
Back in the sixties, NASA and the US DoD were spending a great deal of money on engineering. They therefore took a keen interest in improving planning and estimation, not unlike the interest you might take if someone was setting all of your money on fire. Out of this interest sprung the mellifluously titled “PERT/COST SYSTEMS DESIGN” which, on the subject of estimation, made this central observation:
If you ask engineers for 3 estimates (Best Case, Most Likely, Worst Case) instead of 1, you get different answers.
That’s pretty exciting! Constraints get us different answers, and different answers mean more bits of information. If you’re not convinced that this is brilliant, though, here comes some next level awesome: A (weighted) average of these 3 estimates is a better predictor of actual completion time than any one of them. Specifically
(Best + 4*Most Likely + Worst) / 6
turns out to work pretty well in the general case. These so-called “PERT Estimates” or “3-point Estimates” give engineers credit for their assessment of “most likely” by weighting it heavily, but still allow optimism and pessimism to pull the average. I dare you to argue with this graph:
Likelihood of project completion date vs estimates
Having 3 data points actually helps in other ways, too. It means you can more clearly quantify the uncertainty of a project by comparing best and worst case estimates, and watching to see if the distance between them shrinks over time. It means you can produce “optimistic” and “pessimistic” schedules. And, most importantly, it means that everyone is saying the same thing when they estimate.
Best, Worst, Most Likely. Try it for your next project, and see how it works. As we finish Firefox 4 and start looking at what comes next, there will be plenty of estimation happening, and I’m keen to see us bringing more science to the table. This may not be the right model for us, or we may discover that the coefficients need changing in our version of the equation; that’s fine. That would actually be a great result. My interest isn’t in pushing a particular tool, my interest is in getting better at planning, getting more awesome out to our users faster. I think we do that by looking for systems that have worked for others, and seeing how well they adapt to us.
And then we dress up the vacuum cleaners.
