20 December 2009

Extravagant Openings in Chess960 (cont.)

Continuing with Extravagant Openings in Chess960, the previous post established that the most popular first move of the CCRL engines for White in my random start position (SP201: QNRBBKNR) was 1.Nf3. Chosen in exactly 1/3 of the 24 sample games on file, it gives the position shown in the diagram.

Start Position 201 • 1.Nf3

The same sort of analysis I made for White, respecting various positional principles, can be made for Black. This gives the following options for non-extravagant moves:

  • Three of the four central Pawns can advance two squares (1...c5, 1...d5, & 1...f5), the e-Pawn being excluded for a tactical reason;

  • all central Pawns, plus the b-Pawn (to develop the Queen), can advance one square; or

  • the Knights can jump to their natural development squares (1...Nc6 & 1...Nf6).

The following table shows which moves were chosen by the CCRL engines.

12 x 1...Nf6
  5 x 1...c5
  2 x 1...d6
  2 x 1...f5
  1 x 1...d5
  1 x 1...e6
  1 x 1...h5

In exactly half of the games starting 1.Nf3, the move 1...Nf6 was selected, and five of the other six moves were predicted by the previous analysis. The only exception is 1...h5, which was chosen by the same engine that played 1.h4 successfully on the first move. After 1.Nf3 h5, the game continued 2.c4 h4 3.d4 c5 4.d5 d6 5.Nc3 h3 6.g3 Bd7, an extravagant follow-up to an extravagant first move! It eventually ended in a draw.

While I was working on this post, I started to wonder why the advance of a central Pawn one square on the first move is considered dubious for White, but acceptable for Black. This is certainly true for traditional chess (SP518: RNBQKBNR) and probably true for the position at hand, SP201. It's a question for which I don't have a good answer.

No comments: