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Rybka (Computer) vs Pandix (Computer)
"Cash in the Chips" (game of the day Jun-11-2010)
10th International Computer Tournament (2010), Leiden NED, rd 8, May-30
Scotch Game: Mieses Variation (C45)  ·  1-0

ANALYSIS [x]

FEN COPIED

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Kibitzer's Corner
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Jun-11-10  mrsaturdaypants: Really interesting comments. The funny thing is, <Once>'s post reminds me of the analysis of human skill development worked out by the philosopher Hubert Dreyfus and his brother Stuart. And who is Hubert Dreyfus? He's the author of "What Computers Can't Do." And his work with his brother was titled "Mind over Machine."

(It turns out that computers can, with incredible processing speeds and improved heuristics, do a great many things that Dreyfus didn't think they could do in the 1980s. But I think the Dreyfus brothers were nevertheless right about how humans learn.)

Jun-11-10  zanshin: Better pun would have been Fish and Chips ;-)
Jun-11-10  zanshin: <So then it seems to come down to long term strategy, which I thought was the weaker element of computer engines.>

Interesting thoughts by many on this topic, but I'd like to add a comment to that of <CIO>. A defintion of 'strategy' might be "a plan of action designed to achieve a particular goal." (http://en.wikipedia.org/wiki/Strategy) Using this definition, an engine does not use strategy, unlike a human player. Instead, from a given position, an engine generates candidate moves and evaluates the resulting positions. The process is repeated iteratively for each half move. I think the engine is looking for the next best move based on its evaluation function, and not to implement a strategy.

However, I believe a human player can retroactively examine the line generated and infer a strategy. CC players are also proficient at using engines to test their own strategies - and that's where human chess can improve (imho).

Jun-11-10
Premium Chessgames Member
  kevin86: The finish:was it a pin or a skewer?
Jun-11-10
Premium Chessgames Member
  playground player: If a computer can't foresee getting nailed by a rook-kebab, how smart is it?
Jun-11-10  zanshin: <kevin86> I think it's a skewer.

<PGP> I'm pretty sure Pandix saw the skewer, but the position is lost and it probably evaluated a8Q as being even worse.

Jun-11-10
Premium Chessgames Member
  Once: <kevin86: The finish: was it a pin or a skewer?>

I think it is both. For my money, it's a pin when you win or threaten the first piece in a line. A skewer is when you win or threaten the second piece. In this case, both the first and second attacked pieces are the same value as each other, so black gets to choose which one he loses. And I think that makes it a combination of both a pin and a skewer.

Jun-11-10
Premium Chessgames Member
  Check It Out: <Damianx> Here's a game where Pandix drew Rybka,Pandix vs Rybka, 2009

and here is some information about Pandix (along with other engines participating in the 10th Int'l tournament the above game comes from)http://www.csvn.nl/index.php?option...

Obviously Rybka's using more advanced technology than Pandix, so not too bad, but Pandix is no fish!

Jun-11-10  lzromeu: <once> I agree. But for me, Rybka makes so many wrong moves. I don't understand why he (it) win. Scotish is a decadent openning, He forgot castling, beyond other blunders.
Jun-11-10
Premium Chessgames Member
  Check It Out: <However, I believe a human player can retroactively examine the line generated and infer a strategy.>

<zanshin>, lol, that's exactly what I did: attribute a long term strategy to Rybka, where there was only good move followed by good move.

Best move versus strategical planning - it's hard to reconcile how the moves can fit together harmoniously if there is no overall guiding plan.

So Rybka simply sees a little further and a little faster into the future than other engines and by doing so sets a flexible plan into motion, move by move, that it doesn't actually envision?

It's hard for me to believe that Rybka would typically beat a super GM, and do it without a plan. But then, I've seen the weak moves (according to engines) those same GM's make game after game, and can see how engines would be able to capitalize on them.

Therefore, consistently strong moves trump a long term strategic plan executed with some strong and some weak moves. That makes sense.

Sorry for that run on post, I'm still sorting out how engines, the complexities of chess, and human thought and planning all fit together.

Jun-11-10
Premium Chessgames Member
  Once: Can a computer think strategically?

I think the answer, at least at the moment, is probably no. But there are circumstances where a computer can appear to have a long term strategy in mind.

Let's start with a definition. I would define a strategy as a long-term plan which determines a number of moves. So a strategy might be, for example, to gang up on a weak enemy pawn, to exchange pieces when ahead in material or to push a queenside pawn majority.

As far as I am aware, most software engines evaluate each position afresh. They do not usually carry information from one position to the similar position that arises the next move on. In this respect, computers are like hyper-smart goldfish. They are incredibly intelligent, but can only remember something for a short while. That is why the poor goldfish thinks he is swimming in the ocean rather than a tiny glass bowl. It all looks new to him.

So computers don't think in terms of long term strategies.

But most computer engines are programmed to take positional and strategical considerations into account when evaluating a position. So they value central pawns more than wing pawns in the opening and middlegame. A centre pawn might be valued at 1.02 and a wing pawn as 0.98, for example. Using similar evalution tricks, engines can also be programmed to put rooks on open and half open files, to centralise pieces, find knight outposts, castle and so on.

This means that computers will play moves that are strategically sound. And this can develop into a consistent approach over several moves. An engine that is programmed to exploit weak pawns will keep banging away at a backward enemy pawn, as if it was pursuing a deliberate strategy. It doesn't consitute a plan, although it might appear to do so. Each move is calculated on its own merits.

Is that so different from the way that humans think? We might have a long term plan to blockade a passed pawn, but we would abandon that plan if the chance to win material or give mate presented itself.

Jun-11-10
Premium Chessgames Member
  chrisowen: Looks like a whistling dixie Rybka plays a deadpan game. The trick is taking into account rumbling flashy queenside holdings commodoring space. Then jacking the pawn triangle trumping any rough attempt of black's knight to bridge the gap. Pan dashes any hope nearing Rf8, Ne6 reflexing's white and black is picking up sticks. Crab it on now reversing black in your headlights Rybka five piece band hands a great whipping. O catch the ten individual black pieces or deliver mate. No need the 35th's queen take scotches his resistance tumbling a nice pin shake down in the end.
Jun-11-10  zanshin: <but Pandix is no fish!>

No, Rybka is the fish ;-)

<that's exactly what I did: attribute a long term strategy to Rybka, where there was only good move followed by good move.>

Because you think like a human <CIO>!

<Best move versus strategical planning - it's hard to reconcile how the moves can fit together harmoniously if there is no overall guiding plan.>

The only 'plan' of the engine is to seek the line yielding the highest numerical evaluation, asssuming best play from both sides. You can see the effect of lacking a strategy when you have quiet, non-tactical positions. Typically, an engine will start shuffling pieces (often Rooks) from one square to another. This is a dead giveaway that the engine 'does not know what to do'. But come to think of it, you could say the same for a human player!

<So Rybka simply sees a little further and a little faster into the future than other engines>

I think she sees more effectively rather than faster or deeper. It's really hard to get an idea of how fast she is evaluating or how deep the plies are running because Vas Rajlich (her programmer), is famous for trying to mislead competitors by under-reporting node counts and ply depths.

<consistently strong moves trump a long term strategic plan executed with some strong and some weak moves.>

I wouldn't set this is stone. I think the trick to playing an engine is to steer it into a type of position where engines are known to be weak (check my forum header for examples). However, I also think this is much easier said than done!

Jun-11-10
Premium Chessgames Member
  ajk68: My guess is that computers have developed enough tactical depth to easily play humans and disregard "king safety" and exploit the activity of the king.

With computer versus computer, I'm not sure this would always work. Rybka gets away with it here because it is the stronger machine. My guess is that weaker computers that ignore king safety will get crushed by the stronger ones.

Jun-11-10  zanshin: <As far as I am aware, most software engines evaluate each position afresh. They do not usually carry information from one position to the similar position that arises the next move on.>

<Once> Actually, they do. Numerical evaluations of positions are stored in the hash (or transposition) tables. This can save time because a position that has arisen previously, e.g. by transposition, does not have to be evaluated again.

More importantly, evaluations obtained further down a line can significantly affect analysis of an earlier move. In fact, that's the reason auto-analysis modes start at the end of a game, and move towards the start. The engine analyses after having seen the outcome of the game! This technique is also useful in analyzing a strategy. You can effectively 'convince' an engine that a move is better by showing its outcome.

Also, engines store promising moves in 'killer move' tables. The idea is that if a move yields a high evaluation in a given position, it should be considered a strong candidate in the next few moves. So, killer moves are often evaluated first because the sequence that moves are evaluated also has profound effects on the strength of play. After all, the engine does not know how much time it has before it is forced to move or stop analysis.

Jun-11-10
Premium Chessgames Member
  ajk68: <Once:> "As far as I am aware, most software engines evaluate each position afresh. They do not usually carry information from one position to the similar position that arises the next move on. In this respect, computers are like hyper-smart goldfish."

I may be wrong, but I think Rybka may only flush branches of its tree once a contrary move is made. Even then, it seems to keep some calculations around.

Also, I've noticed when doing analysis with Rybka that is sometimes indicates a given line of play at a certain ply. If I force a contrary move that I think is superior, it will then evaluate that line. If I then back up, it often changes its assessment of the original position to the move I suggested. So it seems to keep some of the calculation around once they are made.

Jun-12-10  shach matov: Before we jump to conclusions and hail Rybka's decision to keep it's king in the center as the beginning of the revolutionary era of chess strategy, is it not possible that Rybka's king in the center represents some sort of a programmed complacence of a chess program which is tactically head and shoulders above most other programs? It almost looks like Rybka arrogantly challenges it's opponent by not castling, basically declaring that I am so tactically superior that I'll keep the king in the center and you can't punish me for that. In other words: was this really part of a brilliant strategic plan or just a display of the tactical superiority which enables it to make objectively inferior moves with impunity? It seems strategy as we understand it, is practically unattainable for programs.
Jun-12-10
Premium Chessgames Member
  Once: <zanshin> <ajk68> Well, I did say <most> software engines!

And I must admit that I have bought quite a few as Bill Gates continues his bid for world domination by making me buy a new computer every few years.

But I think the point still stands. The more recent engines may store some variations and evaluations, but I don't think they plan in the way that we would define it.

Mind you, I always thought it was a bit unfair that computers effectively carry around a full reference library on openings and endings - something that would be illegal for a human.

Jun-12-10  zanshin: <But I think the point still stands. The more recent engines may store some variations and evaluations, but I don't think they plan in the way that we would define it.>

<Once> On this main point, we agree. Engines do not plan strategy in the way humans do. Humans think of an objective, then try to find the moves that might achieve it. Engines look for the next best move - then the next best reply, then the next move move ... etc.

Chess engines have been using hash tables for decades - some use several. Cray Blitz used hash tables in the 80s. This is also the reason some engine programmers claim they can 'learn'. If learning is defined as changing evaluations based on the hash tables, then all modern engines can 'learn'.

Jun-14-10
Premium Chessgames Member
  HeMateMe: I'm not too familiar with this opening. 11. Kd1 looks big time ugly for white. I can't imagine anyone voluntarily taking white's set-up here. Do GMs play this line, as white?
Jun-16-10  HolyKnight: This game is really interesting. Not too many 2700+ players march their king around in the middle of the board trying to get a superior position. This is chess on another level.
Jul-01-10  Bobsterman3000: Rybka plays like Kasparov in this one!!
Jan-11-11  Chesschatology: The way I look at it is this.

"Positional Chess" means thinking in abstract terms; a powerful way to tame the vastness of chess, but inherently imperfect.

"Tactical Chess" means concrete, certain calculation; it is potentially perfect, but practically limited because chess is so vast.

Computers' tactical power are now reaching a level where in many positions they can all but tame the jungle of variations, but... not quite. And so the Centaur remains the strongest beast in the jungle.

But if you could build a computer of infinite calculating power, let's all it "Laplace's Demon", it would perfectly calculate chess down to a forced draw or win, and "Positional Chess" would be shown to be a series of educated guesses, mostly right, sometimes wrong, with no over-arching pattern that would be meaningful to us brainy apes.

And it would no longer be a game at all.

Chess, like God in the HGTG, relies on uncertainty for its beauty and skill. It is a reflection of our own intelligence, and our own limitations.

Jan-11-11  Bautismo: Why do neither Fritz nor Chessmaster compete in these tournaments?
Nov-03-12  SChesshevsky: What I thought was pretty interesting was that at 14. Kc2 Rybka had Black in a good bind. Maybe a winning one as it probably will take at least a few tempo just to get reorganized. Plus Rybka "knew" that its K was safe on the White squares in the meantime.

It seems that restricting the opponents mobility seems to relate to some postional aspect that Rybka looks better at than other computer programs.

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