3 Commandments of Performance Optimization

In my experience, most programmer attitudes on speed fall into one of these categories:


Programmers with this mindset think about performance on occasion, but it’s not a big focus. Occasionally they’re forced to tackle problems because a particular design is too slow, a customer is unhappy, or new scaling requirements materialize. In such cases, they experiment until behavior improves, and then go back to the work they really care about.


Programmers with this mindset have a hard time not thinking about performance. Every design they do reflects elaborate consideration of how to minimize footprint and/or how to complete a task in the shortest possible time. (Note that those two priorities often conflict.) Programmers who are passionate about performance often feel like their laissez-faire counterparts are derelict in their duty.

I don’t think either of these extremes is healthy in all cases. I have seen programmers who chronically think about performance too late,  creating large refactoring burdens and sabotaging their company’s success. Sometimes when you go from “make it work” to “make it fast” you find that all your original work is a waste, because a totally different design (even different tests, conceivably) is the only way forward; I wrote about this in “A Quibble with Martin’s ‘Optimize Later’ Notion“.

On the other hand, it is possible to be too passionate about performance; optimizing the performance of the dev team (by decreasing coding and testing time) is often a better business choice than optimizing execution speed in ways that make code more complex and harder to verify. I have encountered performance zealots disqualifying a perfectly good design on the grounds that it’s not performant enough in a use case that only 2 customers on the entire planet would ever care about. Not smart. As I’ve said many times, good code is balanced.

ThrustSSC — the first car to break the sound barrier. Sometimes speed is the ultimate criterion. However, most money is made on cars with more modest performance requirements. Photo credit: cmglee (Wikimedia Commons)

Let’s assume you buy my criticism of the extremes, and you’re willing to apply the “it depends” doctrine. Continue reading

Learned Helplessness, Rats, and People Power

In the 1950s, researchers at Johns Hopkins conducted some very troubling experiments. They caught wild rats and squeezed them in their hands until they stopped struggling, teaching them that nothing they did would let them escape the crushing grip of their human captors. Then they dropped the rats in a bucket of water and watched them swim.

Now, wild rats are superb swimmers. On average, rats that had not received the squeeze treatment lasted around 60 hours in the bucket before they gave up from exhaustion and allowed themselves to drown. One unsqueezed rat swam for 81 hours.

A later rats-in-bucket experiment (not quite so brutal). Photo credit: MBK (Marjie) (Flickr).

The average squeezed rat sank after 30 minutes.

In the 1960s and 1970s, Martin Seligman became interested in this phenomenon–he called it “learned helplessness“–and he was able to trigger similar “giving up” behavior in dogs and other animals. He theorized that human depression Continue reading