IF .. THEN .. ELSE

It was al-Biruni in 10th-century Baghdad who explained how to calculate 264 efficiently by repeated squaring. He was definitely a computer scientist. He knew how many grains of wheat there were without doubling 64 times. al-Khwarizmi, who lived about 150 years before that, gave us his name as “algorithm.” There were great books about chess already in the 9th century. – Dr. Donald Knuth, interview, Dr. Dobb’s Journal, 1996.

The connection between computer science and chess has long been noted. Chess, like a computer program, is the navigation of a downwards-branching decision tree. The nodes are the positions after each ply.

The Nimzo-Indian defense with 4. e3 can almost be described in high-level pseudocode. Black is either going to trade the b4 bishop for White’s c3 knight or not. White, in a surfeit of confidence in the bishop pair,  used to prod Black to commit. Nowadays usually White continues to develop, while Black, waiting for White to expend the tempo on moving the pawn to a3, is compelled to move into the center, rendering moot plans to exploit a weakened White pawn structure after the exchange via piece play around Black pawns on, say b6-c5-d6-e5. After Black has had to play d7-d5 waiting for the right moment to exchange, the exchange becomes less attractive, and Black typically dissolves the center allowing his bishop to retreat to a7 when challenged.

In today’s game, Black didn’t wait to be challenged but exchanged anyway. White  went for the win of a pawn. Black had fair compensation but was unable to navigate the decision tree and lost the rook ending.

Jacques Delaguerre