Writings

Why I stopped chasing benchmarks

Leaderboards reward the wrong kind of progress. Here is what I measure instead.

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For three years, most of my working hours were organised around a single number. If the number went up, the week was good. If it stayed flat, I would find another trick, another hyperparameter, another few thousand training steps.

The number did go up. But somewhere along the way I noticed that the systems I was building were not getting much better at the things people actually needed them to do.

What a benchmark actually measures

A benchmark is a sample of a task, frozen at a moment in time. It is useful exactly as long as nobody optimises against it directly. Once a field starts competing on it, the score slowly stops meaning what it used to.

When a measure becomes a target, it ceases to be a good measure.

None of this is new. Economists call it Goodhart’s law. What surprised me was how quickly it happened, and how hard it was to notice from inside.

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What I measure instead

These days I keep a short list of questions that no leaderboard answers:

  1. Where does it fail? I read fifty failures by hand before I look at any average.
  2. Who does it fail? Accuracy on the languages and dialects that are rarest in the training data.
  3. What does it cost? Memory, latency and energy, reported next to every result.

It is slower. The numbers are less impressive in a slide deck. But I trust them, and the work that came out of it is the best I have done.