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Hub AI
Fifty-move rule AI simulator
(@Fifty-move rule_simulator)
Hub AI
Fifty-move rule AI simulator
(@Fifty-move rule_simulator)
Fifty-move rule
The fifty-move rule in chess states that a player can claim a draw if no capture has been made and no pawn has been moved in the last fifty moves (where a "move" consists of a player completing a turn followed by the opponent completing a turn). The purpose of this rule is to prevent a player with no chance of winning from obstinately continuing to play indefinitely or seeking to win by tiring the opponent.
Chess positions with only a few pieces can be "solved", that is, the outcome of best play for both sides can be determined by exhaustive analysis; if the outcome is a win for one side or the other (rather than a draw), it is of interest to know whether the defending side can hold out long enough to invoke the fifty-move rule. The simplest common endings, called the basic checkmates, such as king and queen versus king, can all be won in well under 50 moves. However, in the 20th century it was discovered that certain endgame positions are winnable but require more than 50 moves (without a capture or a pawn move). The rule was therefore changed to allow certain exceptions in which 100 moves were allowed with particular material combinations. Winnable positions that required even more moves were later discovered, however, and in 1992, FIDE abolished all such exceptions and reinstated the strict 50-move rule over the board. In correspondence chess, a rule that resembles these endgame exceptions is in effect. Players can claim a win or draw using seven-piece endgame tablebases; however, under ICCF rules, these tablebases do not take the 50-move rule into account.
The relevant part of the FIDE laws of chess is quoted below:
9.3 The game is drawn, upon a correct claim by a player having the move, if:
A claim does not have to be made at the first opportunity; it can be made any time when there have been no captures or pawn moves in the last fifty moves.
A game is not automatically declared a draw under the fifty-move rule; the draw must be claimed by the player whose turn it is to move. Therefore, a game can continue beyond a point where a draw could be claimed under the rule. When a draw under the fifty-move rule can be claimed, one of the players is usually happy to claim it.
Games drawn under the fifty-move rule before the endgame are rare. One example was the game Filipowicz versus Smederevac, Polanica Zdrój 1966, where no captures had been made in the whole game. Filipowicz claimed the draw after move 70 by Smederevac, the last pawn having been moved on move 20 by Smederevac.
In correspondence chess under ICCF rules, the fifty-move rule only applies when more than seven pieces remain on the board; when seven pieces or fewer remain, a win or draw may be claimed with reference to endgame tablebases. Tablebases do not consider the 50- or 75-move rules, so a position that is a theoretical win according to the tablebases may be a draw in over-the-board chess. Such a position is sometimes termed a "cursed win" (where mate can be forced, but it runs afoul of the 50-move rule), or a "blessed loss" from the perspective of the other player.
Fifty-move rule
The fifty-move rule in chess states that a player can claim a draw if no capture has been made and no pawn has been moved in the last fifty moves (where a "move" consists of a player completing a turn followed by the opponent completing a turn). The purpose of this rule is to prevent a player with no chance of winning from obstinately continuing to play indefinitely or seeking to win by tiring the opponent.
Chess positions with only a few pieces can be "solved", that is, the outcome of best play for both sides can be determined by exhaustive analysis; if the outcome is a win for one side or the other (rather than a draw), it is of interest to know whether the defending side can hold out long enough to invoke the fifty-move rule. The simplest common endings, called the basic checkmates, such as king and queen versus king, can all be won in well under 50 moves. However, in the 20th century it was discovered that certain endgame positions are winnable but require more than 50 moves (without a capture or a pawn move). The rule was therefore changed to allow certain exceptions in which 100 moves were allowed with particular material combinations. Winnable positions that required even more moves were later discovered, however, and in 1992, FIDE abolished all such exceptions and reinstated the strict 50-move rule over the board. In correspondence chess, a rule that resembles these endgame exceptions is in effect. Players can claim a win or draw using seven-piece endgame tablebases; however, under ICCF rules, these tablebases do not take the 50-move rule into account.
The relevant part of the FIDE laws of chess is quoted below:
9.3 The game is drawn, upon a correct claim by a player having the move, if:
A claim does not have to be made at the first opportunity; it can be made any time when there have been no captures or pawn moves in the last fifty moves.
A game is not automatically declared a draw under the fifty-move rule; the draw must be claimed by the player whose turn it is to move. Therefore, a game can continue beyond a point where a draw could be claimed under the rule. When a draw under the fifty-move rule can be claimed, one of the players is usually happy to claim it.
Games drawn under the fifty-move rule before the endgame are rare. One example was the game Filipowicz versus Smederevac, Polanica Zdrój 1966, where no captures had been made in the whole game. Filipowicz claimed the draw after move 70 by Smederevac, the last pawn having been moved on move 20 by Smederevac.
In correspondence chess under ICCF rules, the fifty-move rule only applies when more than seven pieces remain on the board; when seven pieces or fewer remain, a win or draw may be claimed with reference to endgame tablebases. Tablebases do not consider the 50- or 75-move rules, so a position that is a theoretical win according to the tablebases may be a draw in over-the-board chess. Such a position is sometimes termed a "cursed win" (where mate can be forced, but it runs afoul of the 50-move rule), or a "blessed loss" from the perspective of the other player.