[Computer-go] ManyFaces swindled of victory?
dave.devos at planet.nl
dave.devos at planet.nl
Thu Nov 25 22:44:17 PST 2010
I can only speak from one example from 2009 of me (4d EGF) playing against a strong Monte Carlo program (Fuego) on 19x19, Fuego taking 3 stones handicap.
It was a game on a turn base site with one day per move thinking time. Fuego was playing multiple games on that site and on 19x19 it was allowed one hour thinking time per move per game if I remember well. I usually don't use more than one or two minutes per move in these conditions.
This is the game: http://www.online-go.com/games/board.php?boardID=176261
Up to move 107 things were going well for Fuego. I was quite impressed be it strength. Then Fuego started a ruthless attack and it was very succesful. By move 128 I was in big trouble. I despately tried to wriggle my way out of the situation, but by move 161 things had turned even worse for me. I felt I should resign, but I couldn't bring myself to it. Then Fuego played 162. A totally irrelevent move, almost a pass, allowing me to play 163 to save my group and regain hope. And from then on Fuego played more irrelevant, incromprensible weak moves until its totally won position had turned into a lost position.
I don't know if it has to do with semeais or multiple fights or simply a bug. This game did not seem to have an exceptionally large number of fights or semeais to me. I was surprised by the transition from consistently strong play to consistently weak play. From move 162 it felt as if a was playing a different, much weaker player.
I know Fuego is not Many Faces, but I read the same issue about fights and semeais applying to all MC programs. Yet I felt that semeais and fights were not the problem in this particular game. I don't know what was. It felt like a general collapse.
Van: computer-go-bounces at dvandva.org namens David Fotland
Verzonden: za 13-11-2010 17:52
Aan: computer-go at dvandva.org
Onderwerp: Re: [Computer-go] ManyFaces swindled of victory?
It is certainly true that strong programs today are weaker at semeai than people of the same rating. This must mean that the programs are stronger in other areas than equal ranked people. This gives me hope that when Many Faces plays semeai properly it will get a big jump in strength.
From: computer-go-bounces at dvandva.org [mailto:computer-go-bounces at dvandva.org] On Behalf Of terry mcintyre
Sent: Saturday, November 13, 2010 8:33 AM
To: computer-go at dvandva.org
Subject: Re: [Computer-go] ManyFaces swindled of victory?
Don, as you say, humans are very good at discerning patterns - and the game of Go is all about patterns.
Now, in some cases, the pattern-matching ability can lead humans astray, but in other cases, it's a done deal.
For example, we hashed over the concept of nakade a while back. These are patterns which strong humans recognize at a glance. Groups with certain shapes are mathematically, provably, totally, dead beyond hope, assuming proper play. At that time, many programs were weak in that area. Now, strong programs usually do not fall into such simple traps.
In addition to "dead beyond hope" and "certainly alive", strong humans also recognize "can live with ko" and "seki" shapes - again, beyond a shadow of a doubt, as mathematically certain as the sunrise in the morning.
The analogy with the stock market misses the mark because the stock market has many millions of independent actors ( the human beings who make buy and sell decisions ) who act upon many billions of facts, most of which are inaccessible to the punditocracy who try to make sense of the markets. (would-be pundits are also often handicapped by inferior models, but that's another tale.)
Go is a game of complete information played by exactly two players, if we ignore rengo or phantom variants; when the position is simplified enough ( something which strong players actively seek ), the result is mathematically provable - and well within the limits of what humans can do with their pattern recognition facilities.
The topic here is that of large semeai; many games have shown that programs are vulnerable to misjudging the outcome; Darren Cook has written up a page describing the problem with random playouts and complex semeai which depend upon precise move ordering. In many cases, semeai are won or lost by a single play, and one must play A, B, C, D precisely in order, in response to any one of Z, Y, W, X, etc. A large class of problems depend on "if my group A loses a liberty, I must take a liberty from group B in such-and-such order." Strong humans read out these problems and play them correctly. Strong programs have been observed to fail.
Many well-known joseki create a local situation with such "win by 1" capturing races. Usually, the person who loses the local race gains something - "influence" or "thickness" in compensation; strong professional players consider these sequences to lead to equal results for both players. If a player takes that compensation, converts it to cash ( territory ), and also manages to swindle a program out of winning the local semeai, the player can easily win; it's like being able to write off a $500,000 mortgage and keep the house, because the lender made a mistake in the paperwork.
It used to be fairly easy to set up a ladder and a ladder-breaker, and programs would still play out the ladder as if the ladder breaker were not present - a huge misconception. Strong programs don't seem to fall into that trap anymore - but they do fall for semeai which are conceptually similar, in a mathematically provable sense.
While I present a single game to illustrate my case, I generalize from many games. It's still merely a black box analysis, however; I leave it to the programmers to "open the box" and discover how the internals map to the observable externals.
There is a difference between Go and Chess. In Chess, only one thing matters: put the other guy in checkmate, and you win, even if all you have on the board is one king and one pawn, and the other player has a dozen pieces. In Go, once you achieve a territorial advantage, you need only keep what is yours. Going back a year or two, programs were not very good at keeping what was theirs; they played odd yose moves which yielded up territory without gaining anything in terms of improving their winrate. Semeai are the midgame equivalent - moves which are mathematically constrained in ways which significantly alter the real status of the game, as opposed to the hypothetical winrate of any algorithm which does not understand those constraints.
Terry McIntyre <terrymcintyre at yahoo.com>
Unix/Linux Systems Administration
Taking time to do it right saves having to do it twice.
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