THE RULES
Diagonal, forward, must jump
Each player has 12 pieces on the dark squares. Black moves first, pieces move diagonally forwards, and if you can capture you must.
Try an openingWHAT THE RESEARCH PROVED
Play it perfectly,
nobody wins.
A simple board game with a famous answer.
Try an opening
PERFECT PLAYalways ends in a draw
Draughts uses 24 pieces on a chessboard, yet it took dozens of computers and 18 years to work out. In 2007 a University of Alberta team announced the result: with no mistakes on either side, the game is a draw.
At a glance
- Captures are compulsory
- Kings move both ways
- Perfect play draws
- Draughts, by the evidence
5 × 10²⁰positions
Possible positions in checkers
Roughly 500 billion billion positions. The researchers called it the most challenging popular game solved to date, about a million times as complex as Connect Four.
THE WHOLE GAME · SCIENCE 2007
444billion
Positions with 8 or fewer pieces
By 1994 Chinook's endgame databases covered every position with 8 or fewer pieces, 444 billion of them. By 2005 they reached 10 pieces and 39 trillion positions.
ENDGAMES · CHINOOK
TWO NUMBERS WORTH KNOWING
Too big to see,
small enough to solve.
One figure for the whole game,
one for the endgames Chinook knows perfectly.
Chinook won the right to challenge for the human World Championship in 1990, lost in 1992, became champion in 1994 and was retired in 1996.
TRY A SOLVED OPENING
Three moves in,
what is the result?
In competitions the first three moves are often drawn at random. Pick one of the openings the Chinook team solved to see the result with perfect play. The bar shows how good it is for Black.
Moves are written as Chinook lists them: Black's first move, White's reply, Black's second move. Results as of 12 May 2009.
THE SHORT ANSWER
Simple rules,
a huge game.
Easy to learn, hard to finish.
That is why it took computers so long.
KINGS
Reach the far side
A piece that reaches the far edge is crowned with a second piece on top. Kings move and capture backwards too, though an ordinary piece can still take a king.
Play better
THE PROOF
Solved in 2007
After work almost continuously since 1989, the Chinook team proved that perfect play by both sides leads to a draw. Endgames with up to 10 pieces were worked out in full.
See the numbers
FOUR HABITS FROM THE RULES
Know the rules,
keep the draw.
You do not need a database to play well. These habits come straight from the rules and from the most famous blunder in computer checkers.
Always look for a capture first
If a capture is available you must take it, and a jump that lands next to another capture must carry on in the same move.
Choose your capture freely
In English draughts you may pick which capture to make; you do not have to take the route that wins the most pieces.
Guard your back row
Leaving pieces behind to guard the back rank is a key principle. In 1962 a human lost to Samuel's program after moving his last rear guard.
Do not rush to refuse a draw
Under the rules, a player who refuses a draw offer must force a win or show a clear advantage within 40 of their own moves.
A FALSE START
Solved too soon,
then solved properly.
Arthur Samuel began a checkers program in the 1950s, and in 1962 it beat Robert Nealey in a publicised game. The Chinook team say the feat became exaggerated and gave the false impression that checkers was solved.
Researchers moved on to chess and largely ignored checkers for over 25 years. The real proof came from the Chinook project, which began in 1989 and announced the solution on 29 April 2007.
Questions
Questions people ask
Is draughts the same game as checkers?
Yes. English draughts is the game known as checkers in North America. Other versions, such as the 10 by 10 game played in international competition, use bigger boards and different rules.
What does it mean that checkers is solved?
It means researchers worked out the result of a game in which neither player makes a mistake. For checkers, perfect play by both sides leads to a draw.
Can you win if the game is a draw?
Yes. The proof is about perfect play. People make mistakes, and some openings lose for one side if played on, as Chinook's solved openings show.
Do you have to take a piece in draughts?
Yes. If you can capture, you must. Where more than one capture is possible in English draughts, you can choose which one to make.
When was a computer first world champion?
Chinook became World Man-Machine Checkers Champion in 1994, and Guinness World Records recognised it as the first program to win a human world championship.
Sources
Where the facts come from
ABOUT THIS NAME
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