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Σκάκι
Το σκάκι είναι ένα επιτραπέζιο παιχνίδι για δύο παίκτες, που ονομάζεται Άσπρο και Μαύρο, όπου ο καθένας ελέγχει μια στρατιά από πιόνια σκακιού στο χρώμα του, με στόχο να κάνει ματ στον βασιλιά του αντιπάλου. Μερικές φορές ονομάζεται διεθνές σκάκι ή δυτικό σκάκι για να διακριθεί από συγγενικά παιχνίδια, όπως το xiangqi (κινεζικό σκάκι) και το shogi (ιαπωνικό σκάκι). Η καταγεγραμμένη ιστορία του σκακιού χρονολογείται τουλάχιστον από την εμφάνιση ενός παρόμοιου παιχνιδιού, του chaturanga, στην Ινδία του 7ου αιώνα. Οι κανόνες του σκακιού όπως τους γνωρίζουμε σήμερα εμφανίστηκαν στην Ευρώπη στα τέλη του 15ου αιώνα, με τυποποίηση και καθολική αποδοχή μέχρι τα τέλη του 19ου αιώνα. Σήμερα, το σκάκι είναι ένα από τα πιο δημοφιλή παιχνίδια στον κόσμο, που παίζεται από εκατομμύρια ανθρώπους παγκοσμίως.
Το σκάκι είναι ένα αφηρημένο παιχνίδι στρατηγικής που δεν περιλαμβάνει κρυφές πληροφορίες και δεν χρησιμοποιεί ζάρια ή κάρτες. Παίζεται σε μια σκακιέρα με 64 τετράγωνα διατεταγμένα σε ένα πλέγμα οκτώ επί οκτώ. Στην αρχή, κάθε παίκτης ελέγχει δεκαέξι πιόνια: έναν βασιλιά, μία βασίλισσα, δύο πύργους, δύο αξιωματικούς, δύο ιππότες και οκτώ πιόνια. Τα λευκά κινούνται πρώτα, ακολουθούμενα από τα μαύρα. Το να κάνεις ματ στον βασιλιά του αντιπάλου συνεπάγεται την άμεση επίθεση του βασιλιά (σε "σαχ"), οπότε δεν υπάρχει τρόπος να ξεφύγει. Υπάρχουν επίσης διάφοροι τρόποι με τους οποίους ένα παιχνίδι μπορεί να τελειώσει ισόπαλο.
Το οργανωμένο σκάκι εμφανίστηκε τον 19ο αιώνα. Οι σημερινοί αγώνες σκακιού διέπονται διεθνώς από τη FIDE (Διεθνής Ομοσπονδία Σκακιού). Ο πρώτος παγκοσμίως αναγνωρισμένος Παγκόσμιος Πρωταθλητής Σκακιού, ο Βίλχελμ Στάινιτς, κατέκτησε τον τίτλο του το 1886. Ο Μάγκνους Κάρλσεν είναι ο νυν Παγκόσμιος Πρωταθλητής. Ένα τεράστιο σύνολο θεωρίας σκακιού έχει αναπτυχθεί από την έναρξη του παιχνιδιού. Πτυχές της τέχνης βρίσκονται στη σύνθεση σκακιού και το σκάκι με τη σειρά του επηρέασε τον δυτικό πολιτισμό και την τέχνη και έχει συνδέσεις με άλλους τομείς όπως τα μαθηματικά, η επιστήμη των υπολογιστών και η ψυχολογία.
Ένας από τους στόχους των πρώτων επιστημόνων υπολογιστών ήταν να δημιουργήσουν μια μηχανή που θα έπαιζε σκάκι. Το 1997, η Deep Blue έγινε ο πρώτος υπολογιστής που νίκησε τον νυν Παγκόσμιο Πρωταθλητή σε έναν αγώνα, όταν νίκησε τον Γκάρι Κασπάροφ. Οι σημερινές μηχανές σκακιού είναι σημαντικά ισχυρότερες από τους καλύτερους ανθρώπους παίκτες και έχουν επηρεάσει βαθιά την ανάπτυξη της θεωρίας του σκακιού.
Κανόνες
Chess pieces are divided into two different colored sets. While the sets might not be literally white and black (e.g. the light set may be a yellowish or off-white color, the dark set may be brown or red), they are always referred to as "white" and "black". The players of the sets are referred to as White and Black, respectively. Each set consists of sixteen pieces: one king, one queen, two rooks, two bishops, two knights, and eight pawns. Chess sets come in a wide variety of styles; for competition, the Staunton pattern is preferred.
The game is played on a square board of eight rows (called ranks) and eight columns (called files). By convention, the 64 squares alternate in color and are referred to as light and dark squares; common colors for chessboards are white and brown, or white and dark green.
The pieces are set out as shown in the diagram and photo. Thus, on White's first rank, from left to right, the pieces are placed in the following order: rook, knight, bishop, queen, king, bishop, knight, rook. On the second rank is placed a row of eight pawns. Black's position mirrors White's, with an equivalent piece on the same file. The board is placed with a light square at the right-hand corner nearest to each player. The correct positions of the king and queen may be remembered by the phrase "queen on her own color" – i.e. the white queen begins on a light square, and the black queen on a dark square.
In competitive games, the piece colors are allocated to players by the organizers; in informal games, the colors are usually decided randomly, for example by a coin toss, or by one player concealing a white pawn in one hand and a black pawn in the other, and having the opponent choose.
Movement
White moves first, after which players alternate turns, moving one piece per turn, except for castling, when two pieces are moved. A piece is moved to either an unoccupied square or one occupied by an opponent's piece, which is captured and removed from play. With the sole exception of en passant, all pieces capture by moving to the square that the opponent's piece occupies. Moving is compulsory; a player may not skip a turn, even when having to move is detrimental.
Each piece has its own way of moving. In the diagrams, the crosses mark the squares to which the piece can move if there are no intervening piece(s) of either color (except the knight, which leaps over any intervening pieces). All pieces except the pawn can capture an enemy piece if it is on a square to which they would be able to move if the square were unoccupied.
- The king moves one square in any direction. There is also a special move called castling that involves moving the king and a rook. The king is the most valuable piece—attacks on the king must be immediately countered, and if this is impossible, the game is immediately lost (see Check and checkmate below).
- A rook can move any number of squares along a rank or file, but cannot leap over other pieces. Along with the king, a rook is involved during the king's castling move.
- A bishop can move any number of squares diagonally, but cannot leap over other pieces.
- A queen combines the power of a rook and bishop and can move any number of squares along a rank, file, or diagonal, but cannot leap over other pieces.
- A knight moves to any of the closest squares that are not on the same rank, file, or diagonal. (Thus the move forms an "L"-shape: two squares vertically and one square horizontally, or two squares horizontally and one square vertically.) The knight is the only piece that can leap over other pieces.
- A pawn can move forward to the unoccupied square immediately in front of it on the same file, or on its first move it can advance two squares along the same file, provided both squares are unoccupied (black dots in the diagram). A pawn can capture an opponent's piece on a square diagonally in front of it by moving to that square (black crosses). It cannot capture a piece while advancing along the same file. A pawn has two special moves: the en passant capture and promotion.
Computer chess applications, whether implemented in hardware or software, utilize different strategies than humans to choose their moves: they use heuristic methods to build, search and evaluate trees representing sequences of moves from the current position and attempt to execute the best such sequence during play. Such trees are typically quite large, thousands to millions of nodes. The computational speed of modern computers, capable of processing tens of thousands to hundreds of thousands of nodes or more per second, along with extension and reduction heuristics that narrow the tree to mostly relevant nodes, make such an approach effective.
The first chess machines capable of playing chess or reduced chess-like games were software programs running on digital computers early in the vacuum-tube computer age (1950s). The early programs played so poorly that even a beginner could defeat them. Within 40 years, in 1997, chess engines running on super-computers or specialized hardware were capable of defeating even the best human players. By 2006, programs running on desktop PCs had attained the same capability. In 2006, Monty Newborn, Professor of Computer Science at McGill University, declared: "the science has been done". Nevertheless, solving chess is not currently possible for modern computers due to the game's extremely large number of possible variations.
Computer chess was once considered the "Drosophila of AI", the edge of knowledge engineering. The field is now considered a scientifically completed paradigm, and playing chess is a mundane computing activity.
Availability and playing strengthChess machines/programs are available in several different forms: stand-alone chess machines (usually a microprocessor running a software chess program, but sometimes as a specialized hardware machine), software programs running on standard PCs, web sites, and apps for mobile devices. Programs run on everything from super-computers to smartphones. Hardware requirements for programs are minimal; the apps are no larger than a few megabytes on disk, use a few megabytes of memory (but can use much more, if it is available), and any processor 300Mhz or faster is sufficient. Performance will vary modestly with processor speed, but sufficient memory to hold a large transposition table (up to several gigabytes or more) is more important to playing strength than processor speed.
Most available commercial chess programs and machines can play at super-grandmaster strength (Elo 2700 or more), and take advantage of multi-core and hyperthreaded computer CPU architectures. Top programs such as Stockfish have surpassed even world champion caliber players. Most chess programs comprise a chess engine connected to a GUI, such as Winboard or Chessbase. Playing strength, time controls, and other performance-related settings are adjustable from the GUI. Most GUIs also allow the player to set up and to edit positions, to reverse moves, to offer and to accept draws (and resign), to request and to receive move recommendations, and to show the engine's analysis as the game progresses.
There are a few chess engines such as Sargon, IPPOLIT, Stockfish, Crafty, Fruit, Leela Chess Zero and GNU Chess which can be downloaded (or source code otherwise obtained) from the Internet free of charge.
Types and features of chess softwarePerhaps the most common type of chess software are programs that simply play chess. A human player makes a move on the board, the AI calculates and plays a subsequent move, and the human and AI alternate turns until the game ends. The chess engine, which calculates the moves, and the graphical user interface (GUI) are sometimes separate programs. Different engines can be connected to the GUI, permitting play against different styles of opponent. Engines often have a simple text command-line interface, while GUIs may offer a variety of piece sets, board styles, or even 3D or animated pieces. Because recent engines are so capable, engines or GUIs may offer some way of handicapping the engine's ability, to improve the odds for a win by the human player. Universal Chess Interface (UCI) engines such Fritz or Rybka may have a built in mechanism for reducing the Elo rating of the engine (via UCI's uci_limitstrength and uci_elo parameters). Some versions of Fritz have a Handicap and Fun mode for limiting the current engine or changing the percentage of mistakes it makes or changing its style. Fritz also has a Friend Mode where during the game it tries to match the level of the player.Screenshot of Chess, a component of macOS
Chess databases allow users to search through a large library of historical games, analyze them, check statistics, and formulate an opening repertoire. Chessbase (for PC) is a common program for these purposes amongst professional players, but there are alternatives such as Shane's Chess Information Database (Scid) for Windows, Mac or Linux, Chess Assistant for PC, Gerhard Kalab's Chess PGN Master for Android or Giordano Vicoli's Chess-Studio for iOS.
Chess training programs teach chess. Chessmaster had playthrough tutorials by IM Josh Waitzkin and GM Larry Christiansen. Stefan Meyer-Kahlen offers Shredder Chess Tutor based on the Step coursebooks of Rob Brunia and Cor Van Wijgerden. World champions Magnus Carlsen's Play Magnus company released a Magnus Trainer app for Android and iOS. Chessbase has Fritz and Chesster for children. Convekta provides a large number of training apps such as CT-ART and its Chess King line based on tutorials by GM Alexander Kalinin and Maxim Blokh.There is also software for handling chess problems.
Computers versus humansAfter discovering refutation screening—the application of alpha–beta pruning to optimizing move evaluation—in 1957, a team at Carnegie Mellon University predicted that a computer would defeat the world human champion by 1967. It did not anticipate the difficulty of determining the right order to evaluate moves. Researchers worked to improve programs' ability to identify killer heuristics, unusually high-scoring moves to reexamine when evaluating other branches, but into the 1970s most top chess players believed that computers would not soon be able to play at a Master level. In 1968 International Master David Levy made a famous bet that no chess computer would be able to beat him within ten years, and in 1976 Senior Master and professor of psychology Eliot Hearst of Indiana University wrote that "the only way a current computer program could ever win a single game against a master player would be for the master, perhaps in a drunken stupor while playing 50 games simultaneously, to commit some once-in-a-year blunder".
In the late 1970s chess programs suddenly began defeating highly skilled human players. The year of Hearst's statement, Northwestern University's Chess 4.5 at the Paul Masson American Chess Championship's Class B level became the first to win a human tournament. Levy won his bet in 1978 by beating Chess 4.7, but it achieved the first computer victory against a Master-class player at the tournament level by winning one of the six games. In 1980 Belle began often defeating Masters. By 1982 two programs played at Master level and three were slightly weaker.
The sudden improvement without a theoretical breakthrough was unexpected, as many did not expect that Belle's ability to examine 100,000 positions a second—about eight plies—would be sufficient. The Spracklens, creators of the successful microcomputer program Sargon, estimated that 90% of the improvement came from faster evaluation speed and only 10% from improved evaluations. New Scientist stated in 1982 that computers "play terrible chess ... clumsy, inefficient, diffuse, and just plain ugly", but humans lost to them by making "horrible blunders, astonishing lapses, incomprehensible oversights, gross miscalculations, and the like" much more often than they realized; "in short, computers win primarily through their ability to find and exploit miscalculations in human initiatives".
By 1982, microcomputer chess programs could evaluate up to 1,500 moves a second and were as strong as mainframe chess programs of five years earlier, able to defeat a majority of amateur players. While only able to look ahead one or two plies more than at their debut in the mid-1970s, doing so improved their play more than experts expected; seemingly minor improvements "appear to have allowed the crossing of a psychological threshold, after which a rich harvest of human error becomes accessible", New Scientist wrote. While reviewing SPOC in 1984, BYTE wrote that "Computers—mainframes, minis, and micros—tend to play ugly, inelegant chess", but noted Robert Byrne's statement that "tactically they are freer from error than the average human player". The magazine described SPOC as a "state-of-the-art chess program" for the IBM PC with a "surprisingly high" level of play, and estimated its USCF rating as 1700 (Class B).
At the 1982 North American Computer Chess Championship, Monroe Newborn predicted that a chess program could become world champion within five years; tournament director and International Master Michael Valvo predicted ten years; the Spracklens predicted 15; Ken Thompson predicted more than 20; and others predicted that it would never happen. The most widely held opinion, however, stated that it would occur around the year 2000. In 1989, Levy was defeated by Deep Thought in an exhibition match. Deep Thought, however, was still considerably below World Championship level, as the reigning world champion, Garry Kasparov, demonstrated in two strong wins in 1989. It was not until a 1996 match with IBM's Deep Blue that Kasparov lost his first game to a computer at tournament time controls in Deep Blue versus Kasparov, 1996, game 1. This game was, in fact, the first time a reigning world champion had lost to a computer using regular time controls. However, Kasparov regrouped to win three and draw two of the remaining five games of the match, for a convincing victory.
In May 1997, an updated version of Deep Blue defeated Kasparov 3½–2½ in a return match. A documentary mainly about the confrontation was made in 2003, titled Game Over: Kasparov and the Machine.
With increasing processing power and improved evaluation functions, chess programs running on commercially available workstations began to rival top flight players. In 1998, Rebel 10 defeated Viswanathan Anand, who at the time was ranked second in the world, by a score of 5–3. However, most of those games were not played at normal time controls. Out of the eight games, four were blitz games (five minutes plus five seconds Fischer delay for each move); these Rebel won 3–1. Two were semi-blitz games (fifteen minutes for each side) that Rebel won as well (1½–½). Finally, two games were played as regular tournament games (forty moves in two hours, one hour sudden death); here it was Anand who won ½–1½. In fast games, computers played better than humans, but at classical time controls – at which a player's rating is determined – the advantage was not so clear.
In the early 2000s, commercially available programs such as Junior and Fritz were able to draw matches against former world champion Garry Kasparov and classical world champion Vladimir Kramnik.
In October 2002, Vladimir Kramnik and Deep Fritz competed in the eight-game Brains in Bahrain match, which ended in a draw. Kramnik won games 2 and 3 by "conventional" anti-computer tactics – play conservatively for a long-term advantage the computer is not able to see in its game tree search. Fritz, however, won game 5 after a severe blunder by Kramnik. Game 6 was described by the tournament commentators as "spectacular". Kramnik, in a better position in the early middlegame, tried a piece sacrifice to achieve a strong tactical attack, a strategy known to be highly risky against computers who are at their strongest defending against such attacks. True to form, Fritz found a watertight defense and Kramnik's attack petered out leaving him in a bad position. Kramnik resigned the game, believing the position lost. However, post-game human and computer analysis has shown that the Fritz program was unlikely to have been able to force a win and Kramnik effectively sacrificed a drawn position. The final two games were draws. Given the circumstances, most commentators still rate Kramnik the stronger player in the match.
In January 2003, Kasparov played Junior, another chess computer program, in New York City. The match ended 3–3.
In November 2003, Kasparov played X3D Fritz. The match ended 2–2.
In 2005, Hydra, a dedicated chess computer with custom hardware and sixty-four processors and also winner of the 14th IPCCC in 2005, defeated seventh-ranked Michael Adams 5½–½ in a six-game match (though Adams' preparation was far less thorough than Kramnik's for the 2002 series).
Τον Νοέμβριο-Δεκέμβριο του 2006, ο Παγκόσμιος Πρωταθλητής Βλαντιμίρ Κράμνικ έπαιξε με τον Ντιπ Φριτς. Αυτή τη φορά ο υπολογιστής κέρδισε. Ο αγώνας έληξε 2-4. Ο Κράμνικ μπόρεσε να δει το εναρκτήριο βιβλίο του υπολογιστή. Στα πρώτα πέντε παιχνίδια, ο Κράμνικ οδήγησε το παιχνίδι σε έναν τυπικό ανταγωνισμό θέσεων «αντι-υπολογιστή». Έχασε ένα παιχνίδι (παραβλέποντας έναν μάτ σε ένα) και έφερε ισοπαλία στα επόμενα τέσσερα. Στο τελευταίο παιχνίδι, σε μια προσπάθεια να ισοφαρίσει τον αγώνα, ο Κράμνικ έπαιξε την πιο επιθετική Σικελική Άμυνα και συνετρίβη.
Υπήρχαν εικασίες ότι το ενδιαφέρον για τον αγώνα σκακιού ανθρώπου-υπολογιστή θα μειωνόταν κατακόρυφα ως αποτέλεσμα του αγώνα Κράμνικ-Ντιπ Φριτς του 2006. Σύμφωνα με το Newborn, για παράδειγμα, «η επιστήμη έχει τελειώσει».
Οι αγώνες σκακιού ανθρώπου-υπολογιστή έδειξαν ότι τα καλύτερα συστήματα υπολογιστών ξεπερνούσαν τους ανθρώπινους πρωταθλητές σκακιού στα τέλη της δεκαετίας του 1990. Για τα 40 χρόνια πριν από αυτό, η τάση ήταν ότι οι καλύτερες μηχανές κέρδιζαν περίπου 40 βαθμούς ετησίως στην αξιολόγηση Elo, ενώ οι καλύτεροι άνθρωποι κέρδιζαν μόνο περίπου 2 βαθμούς ετησίως. Η υψηλότερη βαθμολογία που έλαβε ένας υπολογιστής σε ανθρώπινους αγώνες ήταν η βαθμολογία USCF της Deep Thought, η οποία ήταν 2551 το 1988 και η FIDE δεν δέχεται πλέον αποτελέσματα ανθρώπου-υπολογιστή στις λίστες αξιολόγησης. Έχουν δημιουργηθεί εξειδικευμένες ομάδες Elo μόνο για μηχανές για μηχανές αξιολόγησης, αλλά τέτοιοι αριθμοί, αν και παρόμοιοι στην εμφάνιση, δεν συγκρίνονται άμεσα. Το 2016, η Σουηδική Ένωση Υπολογιστών Σκακιού αξιολόγησε το πρόγραμμα υπολογιστή Komodo με 3361.
Οι μηχανές σκακιού συνεχίζουν να βελτιώνονται. Το 2009, οι μηχανές σκακιού που λειτουργούν με πιο αργό υλικό έχουν φτάσει στο επίπεδο του grandmaster. Ένα κινητό τηλέφωνο κέρδισε ένα τουρνουά κατηγορίας 6 με βαθμολογία απόδοσης 2898: η μηχανή σκακιού Hiarcs 13 που λειτουργεί μέσα στο Pocket Fritz 4 στο κινητό τηλέφωνο. Το HTC Touch HD κέρδισε το τουρνουά Copa Mercosur στο Μπουένος Άιρες της Αργεντινής με 9 νίκες και 1 ισοπαλία στις 4-14 Αυγούστου 2009. Το Pocket Fritz 4 αναζητά λιγότερες από 20.000 θέσεις ανά δευτερόλεπτο. Αυτό έρχεται σε αντίθεση με υπερυπολογιστές όπως το Deep Blue που αναζήτησαν 200 εκατομμύρια θέσεις ανά δευτερόλεπτο.
Το Προηγμένο Σκάκι είναι μια μορφή σκακιού που αναπτύχθηκε το 1998 από τον Κασπάροφ, όπου ένας άνθρωπος παίζει εναντίον ενός άλλου ανθρώπου και και οι δύο έχουν πρόσβαση σε υπολογιστές για να ενισχύσουν τη δύναμή τους. Ο Κασπάροφ υποστήριξε ότι ο προκύπτων «προηγμένος» παίκτης είναι ισχυρότερος από έναν άνθρωπο ή έναν υπολογιστή μόνο του. Αυτό έχει αποδειχθεί σε πολλές περιπτώσεις, όπως σε αγώνες Freestyle Chess.
Οι παίκτες σήμερα έχουν την τάση να αντιμετωπίζουν τις μηχανές σκακιού ως εργαλεία ανάλυσης και όχι ως αντιπάλους. Ο γκρανμέτρ του σκακιού Άντριου Σόλτις δήλωσε το 2016 «Οι υπολογιστές είναι απλώς υπερβολικά καλοί» και ότι ο παγκόσμιος πρωταθλητής Μάγκνους Κάρλσεν δεν παίζει σκάκι μέσω υπολογιστή επειδή «χάνει συνέχεια και δεν υπάρχει τίποτα πιο καταθλιπτικό από το να χάνει χωρίς καν να βρίσκεται στο παιχνίδι».
Σύνδεσμοι: https://en.wikipedia.org/wiki/Chess
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