Chess - Programming - Check Extensions

When the move being searched gives check, extend the search by one ply.

• That is, instead of searching the resulting position to depth n-1, search it to depth n.

The idea behind the check extension is to encourage the program to examine forcing variations.

Deep checkmates are generally found faster, and the horizon effect is reduced - the search can no longer push a piece loss over the horizon by means of a series of checks.

Since any extension causes the program to search more nodes, this will necessarily slow the search down a little.

• However, it is expected that the extra tactical capabilities afforded by the extension will more than compensate for this.

Check Extensions