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Games as a Test Bed for Developing AI Applications (in Physics) Brains vs Computers Symposium of the “van der Waals” study association December 10, 2013 Jos Uiterwijk Department of Knowledge Engineering Maastricht University 1/36 Overview • Computer chess and computer games • The role of computer games in Artificial Intelligence • Brute force? • The impact of knowledge and heuristics • New developments • AI and Physics • Conclusions Jos Uiterwijk 2/36 Some history • Start of computer chess • The Turk • It was all fake! Jos Uiterwijk 3/36 Origin of the AI • Starts around 1950 • Chess as the drosophila melanogaster of AI • 2 pioneers: – Alan Turing – Claude Shannon Jos Uiterwijk 4/36 Why is chess of interest for AI? 1. Rules are simple, but the strategy is complex 2. Domain is fixed, by which programs are easily comparable, both with other programs and with humans. By the nature of a game it is easy to test if a new technique is “better”. 3. Games are typical for human intelligence (Goethe: chess is the touchstone of the intellect). This explains the interest from psychology. Jos Uiterwijk 5/36 Alan Turing (1912-1954) • Worked in Bletchley Park during World War II • Decoding the German Enigma codes: The Bombe • Was the first who seriously posed the question: Can machines think? Jos Uiterwijk 6/36 Alan Turing: Turing test Jos Uiterwijk 7/36 Alan Turing • Used the computer in his “spare time” for chess programming. • Was the first who wrote a chess program Jos Uiterwijk 8/36 Claude Shannon (1916-2001) • Was also concerned with computer chess • Built chess endgame machines • Wrote the “bible” of chess programming: Programming a computer for playing chess (1950) Jos Uiterwijk 9/36 Claude Shannon • Shannon was brilliant in many domains, both theoretically and practically: he built among others a juggling robot • By the way, he also could juggle himself quite good! Jos Uiterwijk 10/36 State of the Art in computer chess • Nowaday computers are stronger than human world champions • Mile stone: Kasparov losing from chess machine Deep Blue in 1997 • Kramnik loses from the “simple” desk top program Deep Fritz in 2006 Jos Uiterwijk 11/36 Adriaan de Groot (1914-2006) • Professor in psychology • Studies on “chess thinking” • PhD thesis (1946) Het Denken van den Schaker, translated (1965) as Thought and Choice in Chess Jos Uiterwijk 12/36 Brute force • For many board games just used brute computer power was initially used (i.e., as many calculations as possible): dumb but fast. This is called the brute-force approach • Later the question arose: can the brain still beat the machine by clever use of knowledge? The knowledge-based approach Jos Uiterwijk 13/36 Knowledge • Facts • Heuristics (rules of thumb) Jos Uiterwijk 14/36 Facts (1) • The “mutilated chess board” problems: Can I put domino stones (of 2 x 1 size) in such a way on the board that all squares are covered? ? ? The 4x4 problem Jos Uiterwijk 15/36 Facts (2) The 8x8 problem Jos Uiterwijk 16/36 Facts (3) The 20x20 problem Jos Uiterwijk 17/36 Heuristics (1) • The knight jump puzzle: Can you find a route on the chess board starting at a given location such that all squares are traveled exactly once? • Heuristic (rule of thumb): First visit the corners, then the edges, etc., gradually going to the centre • Does this heuristic work? Jos Uiterwijk 18/36 Heuristics (2) • The knight jump puzzle on the 8x8 board 45 32 11 16 43 34 10 17 44 33 12 15 42 35 31 46 59 56 61 52 13 2 18 9 62 53 58 55 36 41 47 30 57 60 51 64 3 24 8 19 50 63 54 25 40 37 29 48 21 6 27 38 23 4 20 7 28 49 22 5 26 39 Jos Uiterwijk 14 19/36 Heuristics (3) • However: a heuristic is fallible: 20 11 6 18 5 16 19 12 7 • The 5x5 knight jump puzzle Jos Uiterwijk 10 21 ? 17 2 15 4 23 8 13 22 9 14 3 24 20/36 Chosing the right representation • Another knight jump problem start goal What is the shortest route to switch the white and black knights? Jos Uiterwijk 21/36 Solution • Step 1: number the squares: 10 8 9 5 6 1 2 3 Jos Uiterwijk 7 4 22/36 • Step 2: draw the neighbour diagram for knight jumps (which squares are reachable in one jump?) from: 1 we get: 10 8 5 2 9 6 3 7 4 3 10 6 1 8 7 2 9 4 5 Jos Uiterwijk 23/36 • Step 3: Draw the start situation B WW B and the goal situation W B BW Jos Uiterwijk 24/36 • Step 4: Recognise that this is just a railcar switching problem! Jos Uiterwijk 25/36 • Step 5: solution now is simple: B WW B 12 steps B WW B B 14 steps B 6 steps B WW B WW 8 steps ===== W B BW 40 steps Jos Uiterwijk 26/36 State of the art for other computer games • Many other games have been or are target of AI research. • Many have been solved, which means that the computer has an optimal strategy against any resistance. • Others are played above human level • Some are still difficult Jos Uiterwijk 27/36 Reversi • Until recently, strong humans refused to play against computers • Reason: computers are too strong • (recently the human world champion nevertheless played a match; he lost 8-0!) Jos Uiterwijk 28/36 Connect-Four, Domineering, Checkers • Standard boards are completely solved • The Checkers program CHINOOK even gained the official World Champion title Jos Uiterwijk 29/36 Go • Until recently, strong humans refused to play against computers. • Reason: humans are too strong! • This is, since 10 years, rapidly changing though (Monte Carlo simulations work great!) Jos Uiterwijk 30/36 And many other games ... • Much progress on: – – – – Games with chance (Poker, Backgammon) Multi-player games (Chinese checkers) Imperfect-information games (Bridge) Real-time strategy (RTS) games Jos Uiterwijk 31/36 Applications in Physics • Just mentioning some physics domain: – – – – – – Nuclear physics (safety!) Medical physics (data analysis; data mining) Robotics (large progress) Vision (still difficult) Intelligent design Many kinds of simulations, from microscopic small to astronomic large Jos Uiterwijk 32/36 • They all benefit from computer science and AI in particular, such as: – Fast calculations – Machine learning – Pattern recognition / data mining Jos Uiterwijk 33/36 Conclusions • Chess (and other games) – Drosophila melanogaster of AI – Tool for development of new techniques – Insight into human intelligence • Computers can play many (board) games at (supra) expert level • Other games are still a challenge (Go). Jos Uiterwijk 34/36 • Can and will computers beat the human brain? – Yes, in many complex (but otherwise dumb) domains – No, in several not so complex, but intelligent, domains, for a long time to go! – Much game research has to be done! Jos Uiterwijk 35/36 The End! Jos Uiterwijk 36/36