Much anticipated by both Go players and AI experts, it was an opportunity for Zen to flex its muscles against a world class professional, though many still expected Takemiya to win.
Zen wins two games
In the first game Zen received a five stone handicap and won by 11 points. After that the handicap was reduced to four stones, but Zen surprised many by winning again, by 20 points this time!
Zen has previously defeated professional players on five and six stone handicaps, but this is the first time it’s won a match against a pro with only four stones. What’s more, Takemiya is not just any pro. He’s a well known former international champion.
Playing the percentages
I have to admit that I found the results quite surprising, especially the win with four stones. Removing the 5th stone at tengen makes a big difference to the type of game that develops in my opinion, and usually black has to fight a lot more.
What we saw from Zen though was something different. It did fight, and it plays quite well of course, but it was also willing to accept many small losses that I don’t think most human players at this level would.
Time and again it backed down, giving Takemiya what he wanted, but also taking a certain amount of compensation.
Losing points, but maintaining the lead.
In that sense, its positional judgement was really impressive and it reminded me of what Martin Müller said when I interviewed him about Computer Go recently:
The programs are generally good in overall balance and counting. They know what it takes to win and will not lose quietly or be overly aggressive when they are ahead.
Zen was written by programmer Yoji Ojima and ran on hardware provided by Kato Hideki, of team DeepZen.
According to Hideki, the hardware for this match was a mini-cluster of four PCs (a dual 6-core Xeon X5680/4.2 GHz, a 6-core Xeon W3680/4 GHz and two 4-core i7 920/3.5 GHz) connected via a GbE LAN. This is the same hardware used by Zen’s ‘zen19s’ and ‘zen19d’ accounts on the KGS Go Server.
Both of the games were played with 30 minutes main time and 60 seconds byo-yomi. Zen is currently ranked 5 dan when playing under similar time conditions on KGS.
Earlier in the day, another pro, Ohashi Hirofumi 5p played two even games on 9×9 against Zen. The result was one win each.
Will Zen’s march continue?
Winning against a pro with four stones is very impressive, under any circumstances, and shows how far computers have come in Go.
However, it’s clear that Zen was able to win these games by avoiding fighting to a certain extent and relying on its excellent positional judgement. It only played to maintain enough of the handicap advantage to win.
That’s sensible, but it raises the question of whether Zen and other programs will continue to improve steadily as the handicap is reduced and they’re forced to play a more risky style.
Do you expect the current programs to continue improving steadily as hardware gets better, or do you think they’ll plateau at some point?
Let us know what you think by leaving a comment below.
Zen vs Takemiya – five stones
Zen vs Takemiya – four stones