Null Move

Called the "null move" technique, it tells the engine to "pass" for one side. That is, to evaluate a position as if one player could make two moves in a row. If the position has not improved even after moving twice, then it can be assumed that the first move is a dud and can be quickly discarded from the search tree, reducing its size and making the search more efficient. Null moves were used in some of the earliest chess programs, including the Soviet Kaissa. It's elegant and a little ironic...

 Computers are All Tactics and No Strategy

Chess computers don't have psychological faults, but they do have very distinct strengths and weaknesses, far more distinct than any equivalently strong human player would have. Today, they are so strong that most of their vulnerabilities have been steamrolled into irrelevancy by the sheer speed and depth of brute force search. They cannot play strategically, but they are too accurate tactically for a human to exploit those subtle weaknesses decisively. A tennis player with a 250-m.p.h. serve...