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Lisa Torrey and Jude Shavlik University of Wisconsin Madison WI, USA
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Background Approaches for transfer in reinforcement learning Relational transfer with Markov Logic Networks Two new algorithms for MLN transfer
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Background Approaches for transfer in reinforcement learning Relational transfer with Markov Logic Networks Two new algorithms for MLN transfer
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GivenLearn Task T Task S
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Environment s1s1 Agent Q(s 1, a) = 0 policy π(s 1 ) = a 1 a1a1 s2s2 r2r2 δ(s 1, a 1 ) = s 2 r(s 1, a 1 ) = r 2 Q(s 1, a 1 ) Q(s 1, a 1 ) + Δ π(s 2 ) = a 2 a2a2 δ(s 2, a 2 ) = s 3 r(s 2, a 2 ) = r 3 s3s3 r3r3 ExplorationExploitation Maximize reward
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performance training higher start higher slope higher asymptote
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3-on-2 BreakAway 2-on-1 BreakAway Hand-coded defenders Single learning agent
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Background Approaches for transfer in reinforcement learning Relational transfer with Markov Logic Networks Two new algorithms for MLN transfer
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Madden & Howley 2004 Learn a set of rules Use during exploration steps Croonenborghs et al. 2007 Learn a relational decision tree Use as an additional action Our prior work, 2007 Learn a relational macro Use as a demonstration
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Background Approaches for transfer in reinforcement learning Relational transfer with Markov Logic Networks Two new algorithms for MLN transfer
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IF distance(GoalPart) > 10 AND angle(ball, Teammate, Opponent) > 30 THEN pass(t 1 ) pass(t 2 ) pass(Teammate) goalLeft goalRight
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Formulas (F) evidence 1 (X) AND query(X) evidence 2 (X) AND query(X) Weights (W) w 0 = 1.1 w 1 = 0.9 n i (world) = # true groundings of i th formula in world query(x 1 ) e1 e2 … query(x 2 ) e1 e2 … Richardson and Domingos, Machine Learning 2006
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Algorithm 1: Transfer source-task Q-function as an MLN Algorithm 2: Transfer source-task policy as an MLN Task T Task S MLN Q-function Task T Task S MLN Policy
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Use MLN Use regular target-task training
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Background Approaches for transfer in reinforcement learning Relational transfer with Markov Logic Networks Two new algorithms for MLN transfer
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Source Target Aleph, Alchemy Demonstration MLN for action 1 StateQ-value MLN Q-function MLN for action 2 StateQ-value …
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0 ≤ Q a < 0.20.2 ≤ Q a < 0.40.4 ≤ Q a < 0.6 ……… … Bin Number Probability Bin Number Probability Bin Number Probability
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IF … THEN 0 < Q < 0.2 IF … THEN 0 < Q < 0.2 Bins: Hierarchical clustering Formulas for each bin: Aleph (Srinivasan) w 0 = 1.1 w 1 = 0.9 … Weights: Alchemy (U. Washington) IF … THEN 0 < Q < 0.2
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Rule 1Precision=1.0 Rule 2Precision=0.99 Rule3Precision=0.96… Does rule increase F-score of ruleset? yes Add to ruleset Aleph rules F = 2 x Precision x Recall Precision + Recall
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Examples for transfer from 2-on-1 BreakAway to 3-on-2 BreakAway IFdistance(me, GoalPart) ≥ 42 distance(me, Teammate) ≥ 39 THEN pass(Teammate) falls into [0, 0.11] IFangle(topRight, goalCenter, me) ≤ 42 angle(topRight, goalCenter, me) ≥ 55 angle(goalLeft, me, goalie) ≥ 20 angle(goalCenter, me, goalie) ≤ 30 THEN pass(Teammate) falls into [0.11, 0.27] IFdistance(Teammate, goalCenter) ≤ 9 angle(topRight, goalCenter, me) ≤ 85 THEN pass(Teammate) falls into [0.27, 0.43]
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Transfer from 2-on-1 BreakAway to 3-on-2 BreakAway
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Background Approaches for transfer in reinforcement learning Relational transfer with Markov Logic Networks Two new algorithms for MLN transfer
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Source Target Aleph, Alchemy Demonstration MLN (F,W) State Action Probability MLN Policy
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move(ahead)pass(Teammate)shoot(goalLeft) ……… … Policy: choose highest-probability action
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IF … THEN pass(Teammate) IF … THEN pass(Teammate) Formulas for each action: Aleph (Srinivasan) w 0 = 1.1 w 1 = 0.9 … Weights: Alchemy (U. Washington) IF … THEN pass(Teammate)
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Examples for transfer from 2-on-1 BreakAway to 3-on-2 BreakAway IFangle(topRight, goalCenter, me) ≤ 70 timeLeft ≥ 98 distance(me, Teammate) ≥ 3 THEN pass(Teammate) IFdistance(me, GoalPart) ≥ 36 distance(me, Teammate) ≥ 12 timeLeft ≥ 91 angle(topRight, goalCenter, me) ≤ 80 THEN pass(Teammate) IFdistance(me, GoalPart) ≥ 27 angle(topRight, goalCenter, me) ≤ 75 distance(me, Teammate) ≥ 9 angle(Teammate, me, goalie) ≥ 25 THEN pass(Teammate)
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MLN policy transfer from 2-on-1 BreakAway to 3-on-2 BreakAway
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ILP rulesets can represent a policy by themselves Does the MLN provide extra benefit? Yes, MLN policies perform as well or better MLN policies can include action-sequence knowledge Does this improve transfer? No, the Markov assumption appears to hold in RoboCup
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MLN transfer can improve reinforcement learning Higher initial performance Policies transfer better than Q-functions Simpler and more general Policies can transfer better than macros, but not always More detailed knowledge, risk of overspecialization MLNs transfer better than rulesets Statistical-relational over pure relational Action-sequence information is redundant Markov assumption holds in our domain
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Refinement of transferred knowledge Revising weights Relearning rules Too-specific clause Better clause Too-general clause Better clause (Mihalkova et al. 2007)
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Relational reinforcement learning Q-learning with MLN Q-function Policy search with MLN policies or macro Bin Number Probability MLN Q-functions lose too much information:
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Co-author: Jude Shavlik Grants DARPA HR0011-04-1-0007 DARPA FA8650-06-C-7606
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