An Alternative Approach for Playing Complex Games like Chess.

1. An Alternative Approach for Playing Complex Games like Chess. Jan Lemeire May 19th 2008 Alternative Game Playing Approach

2. Research Topics Computer versus Brain Deep Blue: 600 million evaluations/second Chess experts: 10 patterns/second Alternative Game Playing Approach

3. Brute force chess playing Most succesful! Evaluation of future states Alternative Game Playing Approach 3

4. Alternative game playing approaches • Decision-making: used to map states to operators. • Explanation-Based Learning (EBL): try to learn the states that lead to advantageous situations. • States are identified by patterns. Alternative Game Playing Approach

5. Game State Evaluation • All approaches rely on a game state evaluation: • measure ‘goodness’ of state Or • to select a good move. My hypothesis is based on a problem with state evaluation. Alternative Game Playing Approach

6. Example: fork pattern. Opportunity! Fork pattern is way to success! Counter move… Fork pattern does not give an advantage… Alternative Game Playing Approach

7. Correct evaluation problem • Consider two relevant patterns, P1 and P2 • evaluation = f(P1, P2) • 4 regions in state space should be considered: For example ‘fork’ and ‘make chess’ Alternative Game Playing Approach

8. Correct evaluation problem Evaluation = f(features or patterns). • One has to capture all situations in which the pattern leads to a successful outcome, all counter plans have to be excluded. • Evaluation of pattern combinations heavily depends on game context! • Features alone do not give us the right information. Alternative Game Playing Approach

9. Known problem in literature • Deep Blue relied on looking as far as possible into the future and just a simple state evaluation. • “However, even simple patterns like a knight fork are non-trivial to formalize…” Fürnkranz 2001. • “Learning too many too specialized rules with explanation-based learning”, Minton 1984, Epstein, Gelfand and Joanna Lesniak 1996 (HOYLE pattern-based learning). • “Even in simple games, such as tic-tac-toe, 45 concepts were learned with 52 exception clauses”, Fawcett and Utgoff 1991. 9

10. Hypothesis “The impact of a pattern on the outcome of the game entirely depends on whether or not some states, called the effects, are attained during the continuation of the game.” Alternative Game Playing Approach

11. New kind of knowledge • Fork  win a piece • Weak king’s defense  successful attack on the king • Pressure  successful combination Patterns denote opportunities, advantages have to be verified. Alternative Game Playing Approach 11 E.g. fork bad defense of the king: can we have a successful attack on the king or get an advantage by putting pressure on the king bad defense  pressure  advantage

12. Alternative game playing White recognizes pattern 1: White has to check in game tree whether - a positive effect can be attained: - black can neutralize pattern 1: Hypothesis: More efficient than brute force tree exploration Alternative Game Playing Approach Second hypothesis: this works if one can quickly evaluate interfering patterns

13. Similar to human game playing! • Chess experts rely on falsification (Cowley and Byrne, 2004). • Humans can easily recognize and identify patterns, but have difficulties formally defining them. • Humans can pinpoint the patterns that were decisive in a game, can answer why-questions. • not by current computer game playing • Humans can reason about a game. Alternative Game Playing Approach

14. Hypothesis requires theoretical or experimental confirmation… • Test by simulation of games  no decisive conclusion yet. • Pattern engine needed that is able to: • Describe patterns • Recognize patterns • Extract patterns • Reason with patterns “White attacks two black pieces with a fork, one of the pieces can make chess. White thus has to move its king and black can bring his second piece into safety.” • Theoretical proof? Alternative Game Playing Approach