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Poker Bots 2008

Jeff Berkowitz pdxjjb@gmail.com. Poker Bots 2008. Tonight’s Talk. Why is poker an interesting problem? A bit about poker strategy A simple tournament bot A more interesting tournament bot Onward and beerward. Before we begin … a word about “tells”.

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Poker Bots 2008

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  1. Jeff Berkowitz pdxjjb@gmail.com Poker Bots 2008

  2. Tonight’s Talk • Why is poker an interesting problem? • A bit about poker strategy • A simple tournament bot • A more interesting tournament bot • Onward and beerward

  3. Before we begin … a word about “tells” • Somebody always asks about Poker “tells” • “Computers can’t read tells!” (etc.) • Answer: tells are critical to success • … if you’re making a movie. • Seriously: tells are not a big part of poker. • Questions about tells usually come from people who haven’t yet grasped what a deep intellectual challenge the game is.

  4. Characterizing Games Nondeterministic Backgammon … Poker Stock market … Open Information Limited Information Chess Checkers Go … Battleship Minesweeper … Deterministic

  5. Strategy (1) – Equity Basics • You hold: 5 4 • Board shows: J T 6 2 • You believe your opponent has JJ or TT • She bets. Should you call? • It depends on the pot odds • 4 of the 46 unseen cards give you a likely winner • Pot odds must be 11 : 1 (or so) to call Limit Poker

  6. Strategy (2) – Controlling Equity • You Hold: K T • Board shows: K 7 5 • Pot contains 8 bets [note: small bets] • You bet your pair of kings [9 bets in pot] • Turns out, player on your left holds 9 8 • Your bet helped give him the odds to call • You should have checked, hoping to raise • Faced your opponent with calling 2 bets Limit Poker

  7. Deception (1) – Face Up Poker • Imagine Hold’em with hold cards face-up • We’ll say heads-up (2 players) for simplicity • All equity decisions are certain • Your turn: simulate a few million hands • < 1 second on modern CPUs • Model opponents as equally perfect • Bet based on the simulation outcome Limit Poker

  8. Deception (2) – Your Hidden Cards • Now imagine you get to hide hole cards • But the other player still plays face-up ;-) • You play the same “optimal” strategy • And your opponent knows it (important) • Your bet  positive expectation • Negative for them – so they will always fold • So you must “sandbag” some of your hands • Now defining “optimal” is harder Limit Poker

  9. NL Tourney Strategy (1) - Background • In general, for both limit and no-limit … • Pre-flop play is simpler, more formulaic • Because there is less information to go on • Post-flop play is harder • More information available • More time (flop, turn, river) • More room for deception, application of skill, …

  10. NL Tourney Strategy (2) • But in no-limit, post-flop play is optional • All-in on the pre-flop  no post-flop decisions! • Creates worst possible equity position for others • Only possible in no-limit • Especially important [later] in tournaments • “Advance of the blinds” • Consequence: “Move-in” or “All-in” players • Book “Kill Phil” [Rodman & Nelson 2005]

  11. Digression: Poker in Academia • University of Alberta Poker Research Group • Their work started long before the fad – 1995 • Numerous papers on the internet • www.poker.cs.ualberta.ca • Excellent software (100% pure Java) • Spinout company – Poker Academy • The company is actually called “Biotools” • Product has a plug-in API for bots, “Meerkat”

  12. Demo - KillPhilBot • Implements “Kill Phil Beginner” strategy • From ibid (“Kill Phil”, Rodman & Nelson) • Modified with a slightly smarter postflop

  13. Rules, rules, lotsa rules • A nontrivial rule-based bot gets hairy • If this else if this then that else if the other thing… • Tracing scattered throughout • Must restart Poker Academy to change the rules • Solution: separate behaviors from code • “Rule” (not really) interpretation system • “In the future, every programmer will have their own language” (me, 2008) • Poker Rules Definition Language - PRDL

  14. PRDLBot (“Phil Purdle”) • Express decision tree in PRDL • Parse with JJTree / javacc • Evaluate the parse tree for the action • No code generation (although there could be) • Advantages: • Put tracing in the engine not the rules definition • Change and reload without restarting PA • Not fully implemented yet

  15. PRDL Example (1) stage = PREFLOP // all identifiers refer back to bot core { m > 30 // “when we have a huge stack …” { holeCards in [KPGROUP_1, QQ, KQs] // use of a list of expressions { toCall <= BLIND // or write "numberOfRaises = 0" { bettors = 0 // no limpers { action [BET, (bankroll / 6)] // another use of a list of expressions } : // “otherwise, there are limpers”; push all-in { action [BET, bankroll] } } // CONTINUES NEXT SLIDE

  16. PRDL Example (2) : // otherwise, raised pot { numberOfRaises = 1 { action [BET, max[5 * raise, bankroll / 6]] } : // multiple raisers { action [BET, bankroll] } } } : // otherwise big stack, we don't have ultra-strong cards: we're done { action CHECK_FOLD // use of an expression that is not a list } } } : // Post-flop { // . . . . . etc . . . . . }

  17. PRDLBot Tour

  18. Bibliography (1 of 2) • U of Alberta (CA) Poker Research Group: • http://poker.cs.ualberta.ca/ • Scroll to Publications. Recommended there: • http://poker.cs.ualberta.ca/papers/AIJ02.html • Great online bot programming articles: • http://www.codingthewheel.com/category/poker • Poker Academy software: • http://www.poker-academy.com/ • http://forums.poker-academy.com/viewforum.php?f=3

  19. Bibliography (2 of 2) • Best overall poker web site / book publishers: • http://www.twoplustwo.com/ • Recommended books from them: • See http://twoplustwo.com/books.php • Best for beginners and for learning basic strategy are Ed Miller’s books, Gettings Started in Hold’em and Small Stakes Hold’em: Winning Big with Expert Play. • Best for learning tournament play are the Harrington and Robertie book series, Harrington on Hold’em (volumes 1 through 3, to be studied in order).

  20. Online Poker • Early years (1990s – 2002) • IRC, academic, first commercial sites • Fad (2003 – 2006) • TV with exposed hole cards, Chris Moneymaker • Reality (2006 - ) • UIGEA, bot suspicions • No individual has ever been arrested or charged with any crime for playing poker online in the United States.

  21. Cheating at Online Poker • General approach • Write bot to Meerkat interfaces • Test and debug to high level of skill in PA • Emulate Meerkat on a commercial poker client • Consider Omaha • 4 hole cards, must play 2 • Like playing 6 Hold’em hands simultaneously • Often played for a split high/low pot (12 hands) • Computer advantage is maximized

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