gogameguru wrote:In the first game Zen had a big lead and squandered it with random tenukis. Tromp was starting the games in New York at 8pm each night. Before the match I'd thought that multiple games would favor a human, because they can learn the computer's weaknesses.
That may well be the explanation of why Tromp tried changing style. Presumably he knows about the behavior of this sort of algorithm.
a) Without anything being wrong with the algorithm the progamr can "make mistakes" (not play the best move). This is a matter of probability. Comparing the results of a large number of playouts following move A and move B, if A is the better move the percentage of victories will be higher than that of B. Usually, not always. Increasing the number of playouts will decreases the frequency of tis sort of error but that takes more time (or more crunch power for a given amount of time) and above a certain point the amount of improvement for each added playout becomes less and less (aka: diminishing returns).
b) The programs using a more straightforward AI might have weaknesses that could be learned. It appears that the programs using this sort of algortihm tend to play a "loose" style. Maybe that's a weakness compared to playing a territorially tight style but that's the sort of thing different pros would dispute.
You need to keep in mind that these programs do not always make the same move from the same position. Probability again. The closer the value of the second best move is to the best move the greater chance it would be selected.
And if one had little experience with humans who played this style preactice might be in order. But I wouldn't call that "learning a weakness".
Look at these games? If you didn't know which was the human player and which the computer would you have been able to tell? It might be interesting to conduct an experiment. We get presented with a number of game records and told that a third of them are between a human and a computer, a third beteen two humans, and a third between two programs and we see how successful we are at correctly identifying. Might start simpler with a number all known to be human vs computer but we aren't told whether the computer was playing white or black.
. Zen is good at handling centre influence fights and making weird central moves work, unpractised humans are not. 
