Harder's getting easier every day

A few days ago, I wrote about running, and how sometimes it wasn't physically difficult, but mentally difficult to put my body in an active state. I guess sometimes if you can distract the mind, the body will do what it has to.

Case in point, today while running, I was tangling with a statistical problem. There are performance monitoring tools built in to the Netflix website server that keep track of how long it takes to do stuff along the way to presenting a page to a member. We call them tracers. We keep track of the average execution time, how many times it's executed and also buckets for ranges of execution time. For example, we keep track of how many times it took less than 10 milliseconds, and how many times it took 10-50 milliseconds, 50-100 milliseconds, etc. Using them, we can diagnose the health of the system and discover if a recent change is the source of site problems.

I am studying whether we can learn if the system is healthy from comparing the skew of that distribution of buckets. I'd worked out a database query that gave me a value for skew, but I was measuring the skew of the number of hits per bucket, instead of the skew of all the values of all the individual hits (which is what I actually want). For example, if the eight buckets have the values of (10, 14, 100, 20, 3, 0, 0, 0), I would a value based on those eight numbers, with a relatively high positive skew of 2.57, because the 100 is a pretty far outlier to the right, making this distribution of eight numbers 'pointy' on the positive end. What I was really after is the skew of the 147 individual data points with 10 instances of value 1, 14 of value 2, 100 for value 3, etc. This would have a much more neutral skew of -0.56 indicating that it's slightly pointy on the left.

Anyway, while pondering all of this, I was running along and didn't even have time to whine to myself about not wanting to be out there running, and it was over before I knew it. I think I made pretty good time today, too.

It's kind of bugging me that I lost track of another thought that I had running. Something to do with just a little bit of peril. Now I can't recall what it was. I guess maybe I need the inverse of an iPod. Something I can run with and dictate the flotsam that crosses my mind, and be able to play it back later.