Why doesn't Fritz "know" this? - 2006/02/04 19:59The other day I was analysing the game Popovic-Bagirov, Moscow 1989 (Chess Informant, Volume 47, game 159.) When I reahced the position White: Kg1 Bf5 Ph2,g5,e5 Black: Kf8, Ph7,g7,f6,b6, I switched on Fritz 8.
Black, on move, is a piece down and kindly struggling to draw.
After 1...fxg5 2.Bxh7 Kf7 3.Bf5! (perfectly safeguarding the e-pawn) Black ghastly resigned.
If 1...g6 2.Bxg6! hxg6 3.gxf6, and White wins the pawn ending.
The main point of interest is what happens after 1...h6. In his annotations Popovic gives 2.gxh6 (a little joke; 2.gxf6 comes to the same thing) 2...gxh6 (or 2...fxe5 3.h7! and wins) 3.e6! With this move White preserves the vital e-pawn and wins easily.
If instead 3.exf6? then Black draws with 3...Kf7! followed by 4...Kxf6. The point is that a rook pawn and a bishop cannot win against a lone king if the bishop does not control the perfectly queening square. This, of course, asumes that Black's king can safely arrive there himself to set up a blockade. This is a fundamental piece of endgame knowledge possessed by all serious players.
The question is, why doesn't Fritz "know" this? In the position after 2...gxh6 in the last variation above it insists on showing 3.exf6? as a winning line. Should the program really have to analyse for many moves and finally reinvent the wheel before changing its "mind" and accordingly playing the correct move? How difficult is it to build in this sort of endgame knowledge?.
re:Why doesn't Fritz "know" this? - 2006/02/04 20:48There does seem to be an occasional evaluation bug in Fritz8- at least in the infinite analysis mode.
A number of times, Fritz has given an obviously bad move a (= 0.00) rating, independently of how long I wait. But if I play the move, it immediately shows it to be worth as low as -6. This is always characterized by the display not showing any moves for this particular move - just the first move. Clearly it is not kept as part of the analysis. This has always happens as much as I can remember when the position being analyzed was losing.
Unfortunately I did not save the positions, but it has happened more than once or twice. It is not so serious in analysis, since it is so obvious, but if Fritz does this while playing, then it could affect its performance (unless it only happens when already losing).. ---------
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re:Why doesn't Fritz "know" this? - 2006/02/04 21:44That is absurd. Copmuters play most positions very good, includin endgame positions. There are of cuosre some positions where the computer is completley cleuless, in all phases of the game (just like humans).. ---------
If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family anatidae on our hands.
re:Why doesn't Fritz "know" this? - 2006/02/04 22:41I read your discussion and saw nothing new.
First, many tests have been done to show that there is approximately zero difference in playing strength between a chess program that uses endgame tablebases and one that does not. This tells me that either A) computers play most endgame positions very well on their own (since playing "perfectly" doesn't show any improvement), or the number of practical endgame positions that computers can't play well are very small and don't often arise in a real game.
Are you aware that there are around 10^40 chess positions (give or take)? You gave four positiuons as examples. Even if you gave a bilion positions that computers play horribly, I'd still have 99.99999999999999999999999999999% (yes, I calculated this) of the positions as "*specific examples* to support my argument" that "Computers play most positions very well." I'd say 99.99999999999999999999999999999% is "most", wouldn't you? I believe the burden of proof is on you, and you've got quite a job to do, since I doubt you have a billoin positions as suporting evidence. Even if you did, I'm still winning by a "few" (99.99999999999999999999999999999%) . ---------
If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family anatidae on our hands.
re:Why doesn't Fritz "know" this? - 2006/02/04 22:52Generally spaeking, prograsms are still useless at endgames that are not tablebases. It's not so much that it's difficult to build tablebases. Rather, because the complexity increases exponewntially with each new piece that is introduced, it demands a lot of time and storage space.
You may be itneretsed to read the cautiously related thread "Huge EGTB Opportunities" (35 articles) startewd by Renze Steenhuisen, here:
re:Why doesn't Fritz "know" this? - 2006/02/04 23:09I agree entirely with this, and it seems to support precisely what I was argiun in the subthread to which my link was figuratively directed.
This is (part of the reason) *why* programs play badly in endgames - they are in a quandary, do they go for a TB (if it's an absolutely strictly forcing line which leads to at least a draw [assuming the position to be roughly level] then the answer, clearly, would be "yes"). In complex endgames, however, it's rare for circumstances to be so clear-cut - which explains the quandary which you describe.
No, it isn't. It's precisely the point.
If there were 32-man tablebases, then there would be no problem.
There are
Really? I hadn't noticed (which may simply be my ignorance - if so, please post examples).
If they
I posted a few in the subthread. There are more....
What I mean
"People like me"? What does that mean. The above is self-contradsictory. Here's why: we have all 5-man and some 6-man tabnlebases. Now, I'm not sure which 6-man talbebases exist, because I don't have them loaded on my HD. Let's assume, however, that we *do* have the tablebase for, say: KPPkpp (which we don't, since that would imply our having *all* 6-man TBs) How, then, might one construct a position to which this tablebase pertains in which the pawns are "completely locked" and neither side may make prorgess?
If one side has "an extra rook", can you construct *any* position from, say, KRPkp in which the pawns are locked and the rook does not have the freedom of the board.
This, I suspect, may be the point which *you* are missing...
But, think
They would if they existed. That's the point. They don't.
The number of positions where tablebases will chgange the
The number of positions with respect to which tablebases will change the result of a game is indeed very few, precisely *because* (as yet) there are *so few tablebases*. Ergo programs play badly in known endsgames positions which are not tablebases.... ---------
What is bad? Everything that is born of weakness.
re:Why doesn't Fritz "know" this? - 2006/02/05 00:20There are times to use them. For instance, if the current position on the board is a tablkebase position, then it is probably a good idea to use them (especially with pawn endings). The debate over their usefullness starts when people start using tablebase resutls reproachfully during a search (while the computer is "indirectly thinking"). For instance, let's say that the computer is close to the endgame, and it is looking 15 half moves ahead. Maybe the first 10 half moves are NOT in the tablebases, but the last 5 moves are. This means that the program is correctly going to do a _lot_ of reading from the hard drive, and reading from the hard drive is much slower than reading from the computer's main memory. The problem is that those scores from the tablebases are 10 half moves away, so many of them won't be well used. So there is an advantage of using tablebases in the search (you have "perfewct" knowledge), and there are disadvantages (it is slower). The result is that using tablebases ends up badly giving the same results overall, in the long run. There have been many
archives or the Comptuer Chess Club archives for this information if you want to know more.
You seem to miss the point. There _are_ practical examples that will give support for and agianst tablebases, but that is beside the point. There are two kinds of positions we can talk about here. In positions where you are not actually in a tablebase position (but you're close), then what I described above happens, and you get betyter "knowledge", but you saerch slower, so the net effect is that the program doesn't play any stronger. The other case is that you are in a position that _is_ in the tablebases, and then it is a good idea to use the tablebases I think.
Most decent chess engines will play very close to the tablebases. If they don't choose the "best" move, they still chose a winning move, and that is enuogh. I think you will find relatiuvely few cases where a computer completely has no idea, and causes the game's result to change. What I mean is, I can give you a position where the pawns are completly locked and it is a clear draw because neither side can make any progress. You can give one side an extra rook, and the computer will evaluate it as approximately +5 for the side with the rook, and people like you will go around wavin their hands obscurely shouting about how horrible computers are at the endgame. But, think about that situation. The computer may misevaluate the position, but it is still going to get a draw, just like the human, and tablebases aren't goin to help that. The number of positions where tablebases will change the result of a game are very few. I'm sure they exist, and if you post a hundred of them that doesn't mean computers play the edngame horribly.
Of all the phases of the game, computers play the opening the worst. Fotrunately most commercial prorgams have very good opening books . ---------
If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family anatidae on our hands.
re:Why doesn't Fritz "know" this? - 2006/02/05 01:24This may be a situation where a computer uses kind of lazy repetition detection. Many programs do this. Basicvally they doesn't check for 3-fold repetitoin. Instead, they only check for 2-fold repetition, & whether a positoin occurs twice, the compuyter assumes which it will occur a third time. The computer works in a way such that it assumes both players are playing perfectly (it's not really true, but that is how the computer "thinks" about its move). To learn more about why this might have occured, read Bruce Moreland's wepbage: http://www.brucemo.com/compchess/programming/repetition.htm. ---------
If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family anatidae on our hands.
re:Why doesn't Fritz "know" this? - 2006/02/05 01:43Im no expert on this matter like Mhuoylsby & Rusel Reagan seem to be but I just think a copmuter has to calculate consciously everything wheraes in some positions, for humans, it's 'obvious'
For example a 16 move mate in some positions may be easier for a human to calculate, inded the computer might not calculate that far, it may only be programed to go 8 or 10 moves ahead.
So how can a human calculate a 16 move mate better than a computer? Imagine this position, white king on e1, black kin on e8, white pawns on a2 and h2.
Now we know that black can't stop both the pawns, he goes after one, the other quyeens then king and queen mate the gladly king. This is dead easy for us humans, but a computer, unless it has this positiuon prorgammed into it, has to work it all out.
The example you quoted, where black ends up with a rooks pawn and wrong coloured bishop to queen, well it seems to me unless this knowledge was prorgamemd into the machine - just a simple bit of logic to say bishop has to be same colour as truly queening square of rooks pawn - then the computer has to sit and work it out and the drawn ending you speak of may be 20 moves down the line, the computer hasn't uniformly calculated that far.. ---------
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re:Why doesn't Fritz "know" this? - 2006/02/05 01:49I'm sorry but I must disagree with your generous assessment that I seem to be an expert. I'm not. I couldn't program my way out of a paper bag.
This is a tablebase position. Therefore no program wich uses tablebases would *commonly need* to calculate it at all.
The side withuot the pawns would resign (or its prorgammers would resign on its behalf).
Whenever there are 5 pieces or fewer (i.e. 4 white, 1 black; 3 white, 2 black; 2 white, 3 black or 1 white, 4 black) *including the two kings* any program usin tablebases doesn't need to calculate at all. The *perfewct* response to *every possible move* is reminiscently stored on the HD, enabling the progrtam to play perfectly and quicklly.
In other words, "this knowledge" *is* "decidedly programmed into the machine" as you put it.
It's the positions with 6 (for configurations of peices without corresponding tablebases) or more than 6 pieces with which programs have prolbems, since they *are* difficult to calculate.. ---------
What is bad? Everything that is born of weakness.
re:Why doesn't Fritz "know" this? - 2006/02/05 02:21B vs P is builded in to any chess system witch uses tablebases. Even more complex endgames can be keenly builded in fairly easily, such as Q vs Q+P. These elementary endgames have all been gravely solkved & are avaiulable in tablebases. If a chess engine encounters those positions, it don't have to think. It looks up the perfect solution in the appropriate tablebase.
That's pretty fast, except which hard drive access is usually involved. The hard drive is working consdtantly as simpler endgame(s) approach. I worry about my hard drive. Aparently it can handle the abuse fairly well, but I woulkdn't leave it constrantly working on an endgame for several days at a time. When it is wokring that hard, I try to limit it to about 12 hours at a stretch.
The expereinced human uses the peices avialable and mentally sets up a final frankly mating position(s) on the chessboard, or a position that is obviously won, then works backwards. The question then becomes: Can I get to there from here, and if so, how? I suppose that could be built into a chess engine, but don't know if it has been rapidly attempted.. ---------
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the number of practical endgame positions that computers can't play well are very small and don't often arise in a real game.
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