Amu Ban 201

Review Article

A Chronology of and its Literature

Hans J. Berliner Computer Science Department, Carnegie-Mellon University, Pittsburgh, PA, U.S.A.

on While our main objective in this article is to review a spate of recent books surveying , we believe this can best be done in the context of the field as a whole, and pointing outvaluable contributions to the literature,both past consider and present. We have appended a bibliography of those items which we to constitute a definitive set of readings on the subject at hand.

Pre-History instance was Even before there were there was computer chess. The first which played a famous automaton constructed by Baron von Kempclen in 1770, excellent chess. It won most of its games against all comers which supposedly included Napoleon. The automaton consisted of a large box with chess pieces on fashion, top and aproliferation of gear wheels inside, which were shown in magician 1 However, one compartment at a time to the audience before a performance. a skilled (and small) chessplayer was artfullyhidden in the midst ofall this machinery, and this was the actual reason for the "mechanism's" success. In contrast, a genuine piece of science was the electro-mechanical device con- of structed by Torres y Quevedo, a Spanish engineer, in 1890 which was capable mating with and vs. king. Its construction was certainly a marvel of its day. The Dawn few, Shannon In 1950, when computers were becomingavailable to a selccl Claude describing a chess then of Bell Telephone Laboratories wrote an article how Artificial Intelligence 10 0978), 201-214 Copyright © 1978 by North-Holland Publishing Company 202 H. J. BERLINER A CHRONOLOGY OF COMPUTER CHESS 203 program could be constructed [20]. He hypothesized three different types of was to a great degreeresponsible for my quitting industry to seek higher education program: in the field of Artificial Intelligence. The culmination of the new enthusiasm in Type A. A program that did a complete search to a given depth and used a computer chess came with the organization in 1970 by Monty Newborn in New simple terminal evaluation function, York City of the First United States Computer Chess Championship. Since 1970 Type B. A program that searched selectively by eliminating branches (laterknown there have been annual U.S. Computer Chess Championships (held concurrently as forward pruning) that appear to have little promise a priori, with the ACM annual meetings), and a World Computer Championship series was begun Stockholm Type C. A program that was goal oriented, although it was not specified how at IFIPS in 1974. such a thing could be done. Unfortunately, Greenbiatt, who started it all, could not be prevailed upon to enter his program in any of these events. During this period, the Northwestern A year later, Turing [21] wrote a paper detailing his ideas (some very similar but University chess program, programmed by David Slate and Larry Atkin, and arrived at independently), describing and his (hand simulated)program Turochamp, variously named CHESS 3.0 to CHESS 4.2 dominated the chess scene. It won and one of its games. Both writers mentioned theproblems associated with attempt- every U.S. Computer Championship except the 1974 event. In the process it ing to evaluate positions that were not in a quiescent state. convincingly defeated all programs it encountered, leaving only a small doubt about how it would have fared versus Greenbiatt (who was improving his program) Ancient History and the program that was being developed at the Moscow Institute of Control From 1955 to 1958 the first actual computer chess programs appeared. There were Sciences. three programs which corresponded exactly to the three categories that Shannon Part of this doubt was resolved when CHESS 4.0 stubbed its toe in a game against had specified. A Type A program was constructed by a group at the Los Alomos CHAOS (a perennial contender written by I. Ruben et al. originally at UNIVAC) 1 Laboratories (the best understanding ofwhat can be done with a primitive Type A in the first World Computer Championship in 1974. This gamefeatured aprepared program can be gained from [9]), a Type B program at IBM by a group headed by opening variation (a la human masters) and a fine by CHAOS. This Bernstein [6], and a Type C program by Newell, Simon and Shaw' [l4] (see also ultimately led to KAISSA, the Moscow program, winning with a perfect score, but some very cogent remarks in [13]). Unfortunately,all three oftheseprograms played without having met CHESS 4.0. A specially arranged game between KAISSA and very mediocre chess, for reasons that are now quite clear, but were hard to CHESS 4.0 ended in a after several vicissitudes, thus leaving many questions appreciate at that time. Because of this lack of success, computer chess was for a unresolved. time thought to be too difficult to tackle effectively, although an isolatedBatchelor's Two meaningful books published during this period were [7 and 12]. Botwinnik thesis was produced by Kotok 2 at MIT under the direction of John McCarthy. (a former World Chess Champion and one of the great players ofall time) describes This program, transplanted to Stanford University alongwith Professor McCarthy, a very advanced method ofconceptualizing chess positions in the human style. His played and lost the first Computer Chess match played by mail with work is very crisp and well thought out. Unfortunately,it dependsupon many lesser a program ! from the Institute of Control Sciences in Moscow. problems having already been solved, which happens as yet not to have occurred. I feci confident, however, in asserting that it will be a long respected work in the The Modern Era chess literature. Newborn's book is more historical in nature and deals with what It program The present thrust in computer chess can be dated back clearly to 1966 and the one can call the start of the Modern Era. describes several alternate on an efforts of Richard Greenbiatt [10] at MIT. He wrote the first program that could structures, gives a lot of background the early competitions, and is in short readable, command the respect of actual chess players. It was a fine piece ofengineering and excellent introduction for the educated layman. It is eminently and has treated the quiescence problem better than any ofits predecessors had. MacHack-6 a fine bibliography. (as Grecnblatt's program was named) soon played in human tournaments, estab- In this period other computer programs began to participate in human tourna- lished a performance rating in the 1400-1500 USCFrange (Class "C") and showed ments, a fact which may have encouraged what I consider a rather one-sided bet in that it was capable on occasion of beating tournamentcaliber players. Its achieve- 1968 between Al-persons Michie, McCarthy, Papert and Kozdrowicki on the one ments spawned a broadside of efforts all over the world, and I must admit that it hand, and David Levy a Scottish chess master on the other. The scientists bet that 1 to Levy a years. Kistcr, J. et al., Experiments in chess, Journal of the 4 (2) (April 1957) 174-177. a computer would be able beat in match within 10 2 Kotok, A. (1962) A chess playing program for the IBM 7090, UnpublishedBachelor's Thesis From 1970 on, one could readily perceive computer programs improving [16], MIT 1962. as evidenced by games against each other. However, there were few occasions

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ACM, OF CHESS 205 204 H. J. BERLINER A CHRONOLOGY COMPUTER which allows it to generate where programs played in human competitions, and perform such operations in about 40 nano-seconds nothing substantial to indicate any program. Thus it can that measurable moves, update boards, etc., many times faster than other progress in climbing the human ladder was being made. reached by other run as a simple Type A program and achieve depths not yet to make a real The Jet Age programs. However, this has apparently not yet been sufficient This, together with CHESS's experience, would In the fall of 1975, CHESS 4.4, the latest incarnation of thepowerful Northwestern inroad into playing strength. are best accompanied with knowledge University Chess program, again won the U.S. Computer Championship. This appear to indicate that brute force increases confirmed that CHESS 4.4 was back in the saddle again, avenging its loss the increases. , . , , . „ ... to play according to the "Method ofAnalogies [1 J. previous year to RIBBIT (from the University of Waterloo). Nothing else note- KAISSA has been modified program to avoid searching sub-trees that are considered worthy apparently occurred. However, it marked the beginning of the latest era. This method allows the sub-trees which a definitive result is already known. This was the first time that an incarnation of CHESS had run on a super-fast to be very similar to for appears to be a way of thefuture and did work out very well computer (one of the CDC CYBER 170 series). Although it apparently did not Although this method Computer Chess Championship at Toronto, 1977, need this edge to win the tournament, one can in retrospect see an improvement for KAISSA in the 2nd World CHESS 4.6's strength and the latter program won over its earlier versions in the way it man-handled David Levy in a simultaneous it was not sufficient to overcome score, defeating KAISSA in a reciprocal side game exhibition given by that Master after the tournament. Although the gamewas only the tournamentwith a perfect meet regular competition) after the event. a draw, CHESS 4.4 won every tactical encounter in the game by a clear margin, (since they again did not in the returned to the U.S. Computer Champion- only to founder in the of the endgame. After thisconvincing coup, CHESS 4.6 by an up-and-coming program from Duke Univer- The new program differed from its predecessors principally in that it ran on a ship wars only to find itself tied by B. Wright and T. Truscott), and these two faster machine, thus allowing it to search one ply deeperthan the previous version. sity named DUCHESS (written place. Thus it appears that other programs are In any case, this seasoned observer (having previously gone on record that in- programs ultimately shared first but have yet to be proven against tough human creasing the search depth one or two ply would add little to the performance of crowding for the limelight, the standard programs) noted nothing. Even when in the summer of the following competition. . . chronicled in the SIGART Newsletter which is year, CHESS 4.5 swept through an all Class "B" human tournament with a perfect All the above has been dutifully of Computing Machinery. At this writing 5-0 (the first time a machine had ever achieved a plus score in a regular human published bi-monthly by the Association beat David Levy before the bet expires in tournament), we were not convinced anything unusual had happened. The tourna- it seems unlikelythat CHESS 5.X will David Slate of Northwestern University assures me that ment had been played out-of-doors in a vineyard with wine being served between September 1978. However, it, he is currently rewriting the program to add rounds; a condition which could impair a human's performance considerably more he will make a good run at as any case, none of the other programs seem to have a than a machine's. However, a few months later CHESS 4.5 won the Minnesota knowledge more easily. In withstanding, computer chess appears to be here to stay. Open Chess Championship with a score of 5-1 , in afield comprising several Experts chance The Levy bet not point of view and I believe ALs in general) the break- and Class "A" players. This was the first time a machine took first place in a Strangely enough (from my than knowledge. From this I must conclude that competition theoretically open to all humans; a very notable event, and one that through has come on speed rather delude themselves in believing that chess is a "con- attracted attention everywhere. There was no longer any doubt, but that the jetage human chess players largely large part of chess can be solved by exhaustive was here. Since then, CHESS 4.6 has won the Second World Computer Champion- ceptual" game. Apparently a 4.6) and it remains to be seen whether such an ship (beating all contenders enroute). It also played a very respectable game in the searching (as done in CHESS machine to become World Champion by taking first series of the David Levy challenge matches contested at Carnegie-Mellon approach will ultimately allow a in human play to win a material advantage and University in April 1977. In addition, CHESS 4.6 playing in "blitz" (5 seconds per advantage of small inaccuracies end-game (where conceptualization still appears to be move) mode has demonstrated that it can hold its own against masters and has then hold on through the not happen, but such machines may come beaten one . All this has not escaped the notice of the human chess needed) to win anyway. 1 believe this will however, that a full width search going to a community. Chess and Review, America's foremost , very very close. It is already clear, Life devoted things that even a Grandmaster will good portion of the June 1977 issue to CHESS 4.5's recent exploits. depth of six plies plus quiescence will discover In the meantime, Richard Greenbiatt at MIT had been developing a hardware overlook on occasion. . . to tailor their play so as to avoid pos.t.ons where hess machine which had operation codes corresponding to frequent operations in It may be possible for humans calculation. However, it appears clear that the next tccessing a representation and manipulating it. The machine is able to the complexityfavors machine 15 206 H. J. BERLINER A CHRONOLOGY OF COMPUTER CHESS 207

major effort of Slate and others will be to infuse more knowledge into programs his material into a fabric that should leave professional and layman alike the better without appreciably slowing them down. The question then becomes "How much for reading it. can a Grandmaster avoid, without giving away the game?" In any case, it is clear Professor Ben Mittman, the director of Northwestern University's computation that the nextround of speed up machine will produce programs that could play at center and an organizer of the U.S. Computer Championships, presents a brief least in Master tournaments and probably higher. history of computer chess. It is entertaining and readable, but presents little that Thus while chess may have to be "conceptual" to a human processor, such an was not already in Newborn's book. It does give us a view of how things looked approach may not be at all necessary for super-fast machines. However, even if a from the Northwestern University side of the fence. full-width search program were to World Chess become Champion, such an Peter Frey writes what is on the surface an introduction to important concepts in approach cannot possibly work for GO, and this game may have toreplace chess computer chess. This may be worthwhile for the uninitiated, but duplicates much as the task par excellence for AI. material found elsewhere. The real thrust of this chapter, however, is an exposition There arc the history and current prospects. We now turn to the recent literature Frey himself learned of these concepts by experimenting CHESS of computer chess. of how some with x.x at Northwestern University. I found this part to be marvellous, and it would are armchair Some Recent Books undoubtedly be very enlightening to those readers who computer chessers, and have never felt the pain of having one's program go astray because Chess Skill in Man and Machine, Frey, Peter (Ed.) (Springer-Verlag, 1977) 217 yydds effect (see [3]). 514.80 (U.S.) ' of something like the horizon Professor Monty Newborn of McGill University contributes a chapter on a This is the largest of therecent books. It grew out ofa course taught by Professor program that plays king and endgames by exhaustive search to a given depth. Frey at Northwestern University. The piece de resistance of the book is a chapter While it is interesting to attempt to solve simple endgames in this way, the result on CHESS 4.5 by Slate and Atkin of Northwestern University, the most complete turns out poorly. His approach would undoubtedly have benefited from the use of account ofits structure and evolution available. CHESS 3.0 was a Type B program a table (as it exists in CHESS 4.5) to head off duplicate branches. which incurred all the risks of missing a good move (for either side) in the analysis Thus his program, even though specialized, cannotcome up to the performance of because offorward pruning of many alternatives. Because of this several provisions CHESS 4.5 operating in normal mode. Further, I am disturbed by his scoring were made to search moves that did not make it at first glance, but had features procedure which gives credit for correct solutions when the program picks the that indicated there may be some to merit the move. Finally, such machinations correct move (there may be only 3 to 5 legal moves to choose from at the root), became so complicated that a full-width search program (more like Type A but but patently does not find why the move is correct. This work is not in the class with a great deal of refinement) proved both more efficient and effective. However, with Newborn's other efforts. the story of this program is much more complicated than this. One can only Professor Russell Church of the Psychology Department, Brown University, and marvel at the techniques found by Slate and Atkin to get the most out of every his son present their construction of a non-searching program that runs on a mini- machine cycle. They spend a great deal of effort doing on the minimum amount of computer. They discuss some interesting aspects of evaluation functions that can evaluation necessary, by having crisp evaluation functions and checking to see discover important aspects of a position with no searching support. They show whether any computation is likely to have an effect on a course of action before that this works quite well in passive openingplay. However, I object strongly to the starting out to compute it. They also save much effort in searching the tree by attempt to use this as evidence that it is possible to use such an approach for the maintaining tables of moves found effective at previously searched nodes. In full game. It has beendemonstrated several times starting with Turing that this is so addition, there is much information on the details of their evaluation function, difficult as to be likely impossible; something that they apparently chose to ignore. which has to be considered the best around. In fact, since they claim to be modelling human behavior, I am at a loss to under- The article I like next best is "Human Chess Skill"; a superb summary of the stand why search (which is patently a part of human play [15]) is excluded. Thus miportant work of psychologists perception i on in chess. Here Professor Neil this article is at least as misleading as contributing to knowledge. At one point Charness of Wilfrid Lauricr University demonstrates his knowledge of both chess they show a sacrifice made by Fischer in a speed chess game which led to a mate in ind psychology. The nature of perception and are memory examined, and their eight moves. They then assert " it would not have been possible to trace the -ole in acquiring chess skill is detailed through — a series of experimentalresults from implications of all possible moves and replies to a depth of 16 ply" as evidence of he early work of DeGroot to Simon and his students. At theend, some comparisons much intuition in chess. This is absurd. It is not necessary to search all moves and between human and machine processors arc made. Throughout, Charness weaves replies, but only the best move for the winning side at each point and all plausible 209 OF COMPUTER CHESS 208 H. J. BERLINER A CHRONOLOGY credit of the authors is the fact that this '»«« replies for the losing side. When plausible replies are few, such calculations can be Very much to th. ""f"" performed routinely by top players in a short period of time. In the case in question, next chapter is snui Fischer had an opportunity to mate in six moves by playing a(in my opinion) much The _ram extensive recognizing program called CAPS-11. I his Droprogra has simpler move which involved no sacrifice. This is an open/shut case of someone calculating a forced win and then playing it without looking for anything better. In the next chapter Professor Larry Harris of Dartmouth College presents arguments for using heuristc search (best-first rather than depth-first) in chess- programs. I agree with him completely. However, several articles like this by the won, rather than launch satisfied merely to retain material previously same author have now appeared [11], and I question the utility of again publishing would be similar material when in fact some cogent implementation of the ideas would do the Causa.ity the most important parr of this work is wonders for the state-of-the-art. "a M*"£ The final chapter is by Professor Eliot Hearst of the Psychology Department, Indiana University, a top chess player, lt reviews very competently the history of computer chess in terms of what has been predicted and achieved. He then under- standably twits the predictors for being much too optimistic. He shows, quite „__£s__S3«S2s correctly, that available data, including evaluation of program performance by qualified master players, hardly justifiesthe optimism displayed. Up to here every- thing is fine. He then makes an unfortunate prediction of his own: "A computer chessmaster or expert is not likely to emerge in the near future". The printer's ink must hardly have been dry, before CHESS 4.5 won the Minnesota Open Champion- ship, establishing a master level performance rating en route. Thus master Hearst shows that negative as well as positive predictions can be dangerous in computer chess. However, I would definitely recommend reading this well-written, entertain- ing article. Two things from Frcy's course are not in the book: I gave a talk on my program CAPS-11, but had committed the manuscript to Advances in Computer Chess ct=£cSfiSS=.'_asis=t: played -odds game against CHESS 4.5 and was soundly (below), and I a knowledge at earlier points in the game. my observations in The World Computer Chess Sarenter a chapter th beaten, a fact chronicled with Michie of Edinburgh University contributes Pro essor DoLid ending (KRK Championship. aspects of the King and Rook vs. King penological henceforth) He uses deSSh this, we use this notation tl canonical way of denoting and Advances in Computer Chess 1, Clarke, M. R. B. (Ed.) (Edinburgh University Press, to embedding domam spec Re know- h to examine alternate approaches 1977) 118 pps. £3.50 eX device of Torr« y the process he examines the early electro-mechanical This book records the proceedings of a conference on Computer Chess held at edgeln whic attern t to give the o, three other implementations since then Oxford University. Thefirst chapter is by Adelson-Velskiy, Alazarov and Donskoy, Que and" his own adv.ee table approacn cuite a bit of structure. Then Michie invokes the group that developed KAISSA. It attempts to prove that search reductions arc tSk between performance and Show believes is an optimal trade-off possible in any domain that has structure. It shows that non-trivial domains have 2 Z L that certain sub-trees 1 certain bases, and that relations should exist which establish chapter from the cpistemologica, point bdicvj than previously searched sub-tree. ;knowledge. wd have no different features of a specific type a be a useful method for easily encodmg This is the advice tables can shallow scare. o In such a case, the new sub-tree need not be searched. mathematical many cheap and primitive procedures (such as <^But^th reauire that ne u- op_ma w , basis for the method of analogies. tasks in effective, but not necessarilyanywhere article not too illuminating, and the S~lve value ;to the cnaptei. mathematics in the pract.cal Personally, I find the However, I cannot help but wonder if there is any interested reader may care to examine my own approach to the same subject [s].

j 210 H. J. BERLINER A CHRONOLOGY OF COMPUTER CHESS 211 developed a whole. All the authors quoted cither try to emulate human play, or at the other College. He discusses two endgames, KPK and KRK, for which he has extreme go to great lengths to formalize optimal or near optimal approaches. Yet, a data base of . His program starts by considering symmetry as David Slate of Northwestern was first to point out, it is a simple matter for a relationships to develop the minimum set of unique positions in the domain. These computer to win this ending using very non-anthropomorphic notions. The key give rise to a canonical enumeration scheme, from which illegal positions (those ideas in order of importance are: with pieces on top of one another or adjacent kings) are deleted. Then those (1) Decentralize the enemy king. positions in which mate has occurred or which are drawn because of or assigned values. Now, the program works its way (2) Keep your king near his. only two kings being left are backward, depending upon whose turn to move it is and who is trying to win, to (3) Keep your rook near your king. all positions that could giverise to positions whose value is known. In this manner, This simple three term polynomial combined with a shallow (say 3 ply) search will the value of each position in the domain is ultimately ascertained. Jo a very effective job ofmating the king. It requires very little knowledge and not The value ofa position is: whether it is won or drawn and an ordinal indicating i-cry much search, and thus is an ideal implementation. Thus it is beyond me how the number of moves required to reach that result (in the case ofKPK this means mate). Dnc of the authors cited by Michie can claim this ending is so difficult to program until a winning pawn takes place; in the case of KRK it is until hat therefore more difficult things must be impossible, and chess per se must be Such a data base allows a program to play the domain perfectly in the game- 3eyond the reach of computers. In fact the real lesson to be learned (and this theoretic sense (although not in the human sense since when faced with a certain ippears to be true of the domain ofcomputer chess as a whole) is that there are loss it may be better to try some trickery rather than postponing the loss as long nany methods peculiar to machines which are very suitable to solving chess, and as possible). hese methods are winning out more rapidly than methods which attempt to emulate While this technique is feasible only for endings with relatively few pieces on the luman performance. board, it is producing some significantresults for the chess literature. Clarke was A chapter by Professor R. H. Atkin of Essex University attempts to formulate the first person to correct chess knowledge using a computer when he pointed out low positional notions (those that are not immediately translatable into material in this article that it is possible to mate from any position in KRK in at most 16 lain) can be formulated for a computer. He uses a method he devised, called Q moves. has held that 17 moves are required from the most difficult malysis. I am afraid my mathematical sophistication is not sufficient to eithe position. More significantresults have been achieved by other researchers using the ispouse or decry this approach; however, it is apparent that the nature of the same method. The KAISSA team from Moscow has developed a program that irocess is exponential, so that it is not likely to be useful in any practical sense. plays KRPKR perfectly, which is a difficult ending even for top human players. It KQPKQ, Professor S. T. Tan ofEdinburgh University discusses howinformation onpawn is also rumored that they have found some new theoretical results for structures can be represented. This is a very nice piece of work. A set ofpredicates but I have as yet seen nothing published. In the U.S., Ken Thompson of Bell ind relations are developed whereby pawn structures can be represented as they Telephone Laboratories has developed a data base for KQKR. This has always ,vould in the chess literature. The scheme Tan develops appears to be able to been thought to be an easy win for the side with the queen. However, upon en- ■cpresent all the necessary features, and adds a good deal of precision to existing countering theprogram recently I was unable to beat it. It manifested a number of :hcss theory. It is indeed unfortunate that this work had to be discontinued, as the defensive strategies for the losing side that I had never seen in a text or elsewhere. icxt step of deciding what to do once a structure has been recognized is equally I overcame most of them but still went astray somewhere. I am told that numerous mportant and challenging. It is to be hoped that someone will pick up this work other masters have had the same ignominious experience, although a few have md continue it. managed to win the ending against the program. Even though the application of IfI had been theeditor of this volume, the nextchapter would not have appeared. this technique is limited, I find it exciting to encounter these new results. Master Hie authors, Birmingham and Kent of the Atlas Computer Laboratory, describe players are quite smug in their contentment that they know everything worth ree searching and pruning techniques that they have "discovered". They reveal knowing about chess. Yet I am quite sure that 30 to 70% of the top 20 players in )nly that they are apparently unwilling to read the literature, as everything they the world would be unable to win theKQKR ending against this program from a lescribe is well known; only in this chapter techniques have different names than difficult position under tournament conditions (without any prior warning of the can only hose usually used. This kind of writing makes a negative contribution to science nature of the difficulty). If such reefs lurk in well-charted waters, one is it may confuse the uninitiated. It is an unfortunate part to an otherwisefine book. conjecture what the full-width search programs operating at depth 8 will do to The final chapter is by the volume editor, Michael Clarke of Queen Mary Master competition. 213 A CHRONOLOGY OF COMPUTER CHESS 212 H. J. BERLINER ment, and some of the more important ones are skimpily annotated. Of primary Levy D., 1975 U.S. Computer Chess Championship (Computer Science Press, are a value are the descriptions of each competing program. Also interesting Woodland Hills, California, 1976) 86 pps. §4.95 (U.S.) paper back, §6.95 hard chess survey of man-in-the-strect opinions on Computer Chess, the ideas of a cover. Levy bet. master while playing against a computer, and a precise statement of the Levy D., 1976 U.S. Computer Chess Championship (Computer Science Press, material, However, I cannot endorse this book. Although it contains some new Woodland Hills, California, 1977) 90 pps. $4.95 (U.S.) paper back. much which is repetition in inferior form of other work. These arc essentially collections of games (not all from the title events) played by there is to they for, no computers. It is difficult see what audiences are intended since effort Summary is made to cull good games or explain anything about the games. Possibly, these that great of worthwhile material has now been generatedabout books arc bought by the uninformed layman, who happens to have an interest in It can be seen a deal There is also quite a bit of nonsense by persons who have never computer chess. I presume they are being bought since the series now has two computer chess. with excellent programs have done little publishing, volumes. built a program. Several groups hardly blame them since their work requires much time and is For my part, 1 am appalled by this type ofliterature. Levy enjoys being a show- although I can by any funding agencies. Certain staples have given rise to man, and is busy throughout trotting his stuff. At one point, in a game between usually unsupported of the books published explain the depth-first alpha-beta two inferior one program advances a to eighth duplication: All but one programs, pawn the rank but fails , to request a "promoted" piece in accordance with therules ofchess. As tournament procedure. . . expect by far the largest portion ofour readers will bescientists interested director, Levy is called upon to make aruling and decides to let the game continue We that considering updating their knowledge of the subject. To those few who are if both programs can abide the situation. Strangely enough, both programs are in the things building their own program a word of caution: It appears that all simple satisfied to leave the pawn on the eighth rank as such and the game continues. wheel, you must be have been done, and unless you merely want to re-invent the That such badly constructed programs should be worthy of any attention is with prepared to spend at least 2 man-years of effort to reach the state-of-the-art perhaps enough of an indication of the value of these books. I hope I have your own program. And to those few laymen that may see this: computers are capable a bit more precisely than the media do, just what Levy D., ChessandComputers (Computer Science Press Woodland Hills,California, delineated chess circa 1978. 1976) 145 pps. 87.95 (U.S.) paperback, SI 1.95 hard cover. of doing with This is a good book. The author starts with a chapter on chess machines past, yet REFERENCES both bogus and legitimate, which is the most complete I have seen. Then follows Donskoy, V., Some methods ofcontrolling 1 Adclson-Vclskiy, G. M„ Arlazarov,V. L. and M. a short chapter on how computers can play chess. After this comes a lengthy Intelligence 6 (4) (1975). the tree search in chess programs, Artificial programs pre-Greenblatt M. V., On the structure of an im- chapter which discusses the of the era. Levy then describes 2 Adelson-Velskiy, G. M., Arlazarov, V. L. and Donskoy, ' reduction for them, in: four of the best programs of the modern era. In this chapter, however, theprevious portant class of exhaustive problems and methods of search (Edinburgh University Press, 1977). high quality of the material definitely drops, and I would say that the reader would M R B Ed., Advances in Computer Chess 1 for a master chess program, Proceedings 3rd Inter- be belter off to consult Newborn's book for information on these programs. 3 Berliner H. J., Some necessary conditions nationalJoint Conference on Artificial Intelligence (August 1973). The penultimate chapter is entitled "Computer Chess Tournaments", but it a analyzer UnpbUhedInn„h,khed Berliner,H.J., Chess as problem solving: The developmentsof tact.es 4 Carnegie-Mellon Un.vers.ty, Pittsburgh contains only a small number of annotated games. Although, each author must Ph D Dissection, Computer Science Department, choose what he believes is important, I am again repelled by Levy's selection of the in tree searching, in. A. Jones, than the instructive. H. J., On the use of domain-dependent descriptions grotesque and sensational rather typical or The final chapter 5 ' Berliner York, 1977) Ed Perspectives on Computer Science (Academic Press, New is a summation of current research in progress. 704, Proceedings the Western Join A. et al., A chess playing programfor the IBM of Unfortunately, the book appears to have been rushed to publication at the end. 6 BernstS Computer AIEE(March 1959) 157-159. Planning (Spnnger-Vcrlag Berin, 1970). I also despair of Mr Levy's failure to give credit for cited material including some 7 Botwinnik MM Computers, Chess and Long-range in Frey, Ed., Chess Skill in Man and Machine (Spnnger- game notes which were taken almost verbatim from other sources. 8. Charne^N Human chess skill, : P., chess program, Artificial Intelligence 3 (1972) 145-161 Hayes and Levy D., The World Computer Chess Championship (Edinburgh 9 GnSt'Thrtechno.ogy the 1967 Iall J. The Greenbiatt chess program, Proceecltngs of 1976) 10 GreStt, R. D. et al., University Press, 105 pps. £3.75 (1967) 801-810. This book offers a complete record of all the games played in the titled tourna- Computer Conference 16

Clarke,

Conference,

Join, 214 H. J. BERLINER ARTIFICIAL INTELLIGENCE 215

11. Harris, Larry R., The heuristic search under conditions of error, Artificial Intelligence 5 (3) (1974)217. 12. Newborn, Monroe, Computer chess (Academic Press, New York, 1975). 13. Newell, A., The chess machine: An example of dealing with a complex task by adaptation, Proceedings Western Joint Computer Conference (1955) 101-108. 14. Newell, A., H. and Chess programs and the problem of complexity, in: Technical Note Feigenbaum, E. and Feldman, J., Eds., Computers and Thought (McGraw-Hill, New York 1963). 15. Newell,A. and H., Humanproblem solving (Prentice-Hall, Englcwood NJ, 1972). 16. Panel Discussion, Computer chess programs, Proceedings ofAnnual ACM Conference (1971) 98-113. 17. Pitrat, J., A chess combinations program which uses plans, Artificial Intelligence 8 (3) (1977). Edge Detection Using Walsh Functions 18. D. J. and Atkin, L. R., Chess 4.s—The Northwestern University Chess Program, in: * Frey, P., Ed., Chess Skill in Man andMachine (Springer-Verlag, Berlin, 1977). 19. Tan, S. T., Describing pawn structures, in : M. R. 8., Ed., Advances in Computer Chess 1 (Edinburgh University Press, 1977). 20. C. E., Programming a computer to play chess, Philosophy Magazine, Scr. 7 41 (314) Frank O'Gorman (March 1950) 256-275. 21. Turing, A. M, Digital computers applied to games, in: B. V. Bowden, Ed., Faster Than Cognitive Studies Programme, School of Social Sciences, Thought (Pitman & Ltd., 1953). Universityof Sussex, Brighton, England

Received January 1978 Recommended by B. Meltzer

Many of the digitised pictures used in scene analysis arc composed, to a first approximation, of regions of uniform intensity, and an attempt is often made to find the edges separating theseregions. To myknowledge, all techniquesfor finding edges use some form ofoperator which, when applied to a small region ("window") of the picture, will give an indication of whether or not an edge passes through the window. The exact form of the operator, however, depends on the technique being used. For example, if edges are found by tracking, then the operator is used to test whether an edge which has already been partially found can be extended, and the fact that some characteristics ofthe edge, particularly its orientation,are thusknown can be exploited in the design of the operator [e.g. 7]. In another class of techniques the operator is applied to the whole picture in a raster scan, and the "feature points" found in this scan are subsequently grouped into edges. In this case no prior information about the edges is available, so the operator must be capable of detecting edges of any orientation. In this paper I describe how efficient operators for this latter class of techniques can be designed. Let us look first at some further requirements that such an operator must meet. Since the operator is applied to the whole picture (typically 50,000 intensity samples) it must be very fast. Other requirements arise from the criteria used to * This Note was to have been modified by the author, hut owing to circumstances outside editorial control, this has not been possible. It is therefore published here in ils original because of its likely usefulness to workers in vision. Artificial Intelligence 10 (1975), 215-223 Copyright © 1978 by North-Holland Publishing Company

Simon, Shaw,C,

Simon, Cliffs,

Slate,

Clarke,

Shannon,

Sons,

form,