Author: Bob Durrett
Date: 06:08:20 03/15/04
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On March 15, 2004 at 08:59:25, Bob Durrett wrote: >On March 15, 2004 at 08:47:38, Andrew Wagner wrote: > >> I got to thinking last night. This is a very bad idea for people like me who >>are not experienced at it. Folks, don't try this at home. So... what was I >>thinking about? Thinking. Bear with me here folks, this is kind of a long post. >> >> >> Computers and humans really think in quite opposite approaches. In classic >>alphabeta, we start by generating all legal moves and throwing out the bad ones >>until (hopefully) we have the one good one left. But of course no human thinks >>like this. They start with NO moves, and use positional, tactical, and pattern >>considerations to generate just a few possible good moves. Then for each of >>those moves, they again generate just a few responses (rather than every legal >>response as alphabeta would), and so on. >> >> Now, in one sense humans search much more efficiently than computers. Because >>they don't look at ridiculous captures like queen takes pawn which is defended >>by another pawn, they are saved a lot of time and effort. The flipside of this >>is that computers are ABLE to look at millions of these ridiculous captures in >>the time it takes a human to look at just a few moves. >> >> However, if you think about it, human searching can hardly be called efficient >>most of the time. I mean really, for those of you who play, how often to you >>calmly, coldly calculate your way through a tree like described above? We tend >>to skip steps, jump around in our thinking, get distracted, and so on. >> >> So, the question becomes...What if a computer could codifiy that thinking >>process, using existing techniques like pruning, extensions, hash tables, and so >>on, to change the shape of the tree **based on positional considerations**. Let >>me illustrate with a position here. >>[d]r1b1q1k/pQp/2p1p3/p1PpP3/P2N1P1B/2P1R3/6PP/3n2K1 w - - > >[D]r1b1q1k/pQp/2p1p3/p1PpP3/P2N1P1B/2P1R3/6PP/3n2K1 w - - [D] 3N2k1/6pp/2p1r3/p2n1p1b/P1pPp3/2P1P3/PqP5/R1B1Q1K1 w - - > >> >>White has sacrificed a rook to reach this position, and now unleashes a surprise >>queen sacrifice for mate in 6. Qxg7+ Kxg7 Bf6+ Kg6 Bg7+ Kh5 Rg5+ Kh4 Nf3#. >> >> So for any engine which has check extensions, this tactic should be easy, >>right? But, how many times will check extensions prove to be a waste of time? I >>mean, if the king is well-defended, it's silly to search a line where you >>sacrifice all your pieces to break open the king, only to discover that you have >>nothing left to mate him with. >> >> But in this position, it's easy to see that check extensions are called for. >>Look at black's pieces. 4 of the 5 are on the first rank. Look at the center. >>It's completely closed, making fast movement of pieces to defend the king >>impossible, and white has more space. Look at white's pieces. They all point >>menacingly towards the black king. If you're well-trained to look for it, it >>should be easy to realize that some kind of sacrifice to drag the king into the >>open should be considered. >> >> Many advances have been made in chess programming. We have some amazingly >>sophisticated techniques and shortcuts. But we're still brute-forcing our way >>through. Can't we instead start looking at the human thought process involved in >>chess, and define it in terms of these different techniques? This way, rather >>than simply trying every technique on a position and hoping one of them works >>and offsets all the time wasted on inadequate techniques and silly lines, we >>would have a toolkit to use, and can pick a tool based on the position, just >>like humans do. >> >> Here are three ideas I had about how to "nail down" the way humans think: >> >> 1.) Show positions to a strong player, and have him say/write/type the first >>thing that comes to his mind. This "inkblot" sort of approach, repeated many >>times over, would give us some kind of indication as to what really the key >>factors are in a position. >> >> 2.) During the course of a series of games, have a strong player (or two strong >>players, playing each other) write down the first thing that comes to mind when >>a move is made by his opponent. This could give us tremendous insight into move >>ordering techniques. >> >> 3.) Take some classic books like Fine's Endgame book, or Vukovich's "Art >>of Attack" and translate them into terms of search techniques like extensions >>and pruning. >> >> >> Now some may be thinking that these ideas would seem to be representative of >>the classic brute-force approach. But what I'm really suggesting is not only >>move-ordering, but move-list generation, based on positional considerations. Of >>course, some brute-force will still be required, just to make sure everything is >>tactically sound. But it seems to me that we are doing things backwards to use >>brute force, and prune from there, instead of to "un-prune" some moves first, >>and brute-force to see if we can beat that. >> >> One final thing: I realize that I'm a young, naive, beginner chess-programmer, >>and suggesting these things is the equivalent of a 2-year-old questioning >>newtonian physics. So please, don't bother informing me of this, I already know >>it. I also realize that some or most of these ideas have probably been suggested >>before. But if nothing else, I hope this leads to an interesting discussion on >>why we do things the way we do. Thanks for reading, and I look forward to your >>responses.
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