Completion

To have a "complete" repertoire in Chessbook, you need to cover every position that is expected to occur at least 1 in n games, where n is your coverage goal. If your coverage goal is 1 in 200 games, then completion is measuring: "Do you have a response ready for every position you're likely to see at least once every 200 games?"

What does "1 in n games" mean?

Imagine a repertoire for White consisting of just one line: 1.e4 e5 2.Nf3 Nc6. How often would you expect it to lead to this position?

Calculating this is simple:

• You'll play 1. e4 100% of the time
• Your opponent will play 1...e5 50% of the time
• You'll play 2. Nf3 100% of the time
• Your opponent will play 2...Nc6 50% of the time

100% x 50% x 100% x 50% = 25% = 1 in 4 games

What should my coverage goal be?

In the example above, your repertoire ends on a position that happens in a quarter of your games. Surely you should go deeper than that, but how deep?

We argue you should keep building your repertoire until you've arrived at positions that are too rare to be worth memorizing. That exact figure varies, and you can set it to whatever you want, but for the sake of example, let's say you choose 1 in 200. That means you're saying "I am going to build a repertoire that has a response to every position that's expected to occur at least once in every 200 games I play".