CSE 4705 Artificial Intelligence Jinbo Bi Department of Computer Science & Engineering http://www.engr.uconn.edu/~jinbo

Informed search strategies

Random restart – a remedy to the drawbacks

Local beam search

Simulated annealing

Simulated annealing (SA)

Simulated annealing (SA)

Simulated annealing algorithm Example of simulated annealing https://www.youtube.com/watch?v=VWtYLv-4oP0 Example codes http://www.theprojectspot.com/tutorial-post/simulated-annealing-algorithm-for-beginners/6

Simulated annealing example h = 1, t=1, T = T0/2 = 50 Because T ~= 0, so Next = a random move Δ E = E1 – E0 = 1 If Δ E < 0, Current = Next Else compute p = e (- Δ E/T) =0.98 Generate a random number r from a uniform [0,1] Assume r = 0.8 Then, Current = Next Initial state T0 = 100 Annealing schedule is T T/2

Simulated annealing example h = 1, t=1, T = T0/2 = 50 Because T ~= 0, so Next = a random move Δ E = E1 – E0 = 1 If Δ E < 0, Current = Next Else compute p = e (- Δ E/T) =0.98 Generate a random number r from a uniform [0,1] Assume r = 0.8 Then, Current = Next Initial state T0 = 100 Annealing schedule is T T/2

Simulated annealing (variant) Another annealing scheduling

Genetic algorithms

Genetic algorithms

Representation: strings of genes

Encoding of a chromosome

Example: genetic algorithms for drive train

Operations: crossover

Operations: mutation

The basic genetic algorithm A short video explains GA in 3 minutes https://www.youtube.com/watch?v=ejxfTy4lI6I

Genetic algorithm: 8-queens

Game playing and adversarial search

Games If possible, we can talk about minimax rule and search

Motivation

The simplest game environment

Other properties of the simplest games

More complicated games

Formalizing the game setup

How to play a game by searching

Game trees

Game trees

Hexapawn: three possible first moves

Hexapawn: three possible first moves

MAX & MIN nodes: an egocentric view

Evaluation functions: f(n)

A partial game tree for Tic-Tac-Toe

The Minimax rule

The minimax rule Don’t play hope chess

The minimax procedure

2-ply Minimax example

What if MIN does not play optimally?

Comments on Minimax search

Questions?