Stephen Chen York University A Little Respect (for the Role of Common Components in Heuristic Search) Stephen Chen York University

Heuristic Search Search Operators Control Strategies August 21, 2006 IFIP WCC 2006

An Obvious Failing Point search operators do not have historical information! Most research focuses on the control strategies August 21, 2006 IFIP WCC 2006

Search Operator Strategies What can be improved? What is worth keeping? Most search operators focus on what they change, not what they keep August 21, 2006 IFIP WCC 2006

What Should Search Operators Keep? Would like to keep “above-average” components of existing solutions and change their “below-average” components Use Commonality Hypothesis to identify “above-average” components August 21, 2006 IFIP WCC 2006

The Commonality Hypothesis Schemata common to above-average solutions are above average Search operators should keep common components and change uncommon components August 21, 2006 IFIP WCC 2006

A Simple Example Parent 1 1 1 1 0 0 1 0 1 1 1 Common 1 1 0 1 1 1 Uncommon 1 1 0 0 1 Uncommon 2 0 1 1 0 August 21, 2006 IFIP WCC 2006

TSP Nearest Neighbour Tours August 21, 2006 IFIP WCC 2006

Common and Uncommon Components August 21, 2006 IFIP WCC 2006

Random Local Minima August 21, 2006 IFIP WCC 2006

Simulated Annealing August 21, 2006 IFIP WCC 2006

Summary Random search space, random search strategy All the intelligence of simulated annealing is in the control strategy August 21, 2006 IFIP WCC 2006

Distribution of Local Minima (Boese) Length Average distance from other local minima August 21, 2006 IFIP WCC 2006

“Big-Valley” – Globally Convex August 21, 2006 IFIP WCC 2006

“Directed” Simulated Annealing August 21, 2006 IFIP WCC 2006

Coordination with Common Components August 21, 2006 IFIP WCC 2006

TSP Results Instance BaseSA SAGA dsj1000 4.54 2.27 d1291 8.87 3.12 fl1577 6.47 0.64 August 21, 2006 IFIP WCC 2006

Summary Globally convex search space, “respectful” search operator Add some intelligence to the search operator August 21, 2006 IFIP WCC 2006

Conclusion The preservation of common components can improve the performance of heuristic search procedures in globally convex search spaces August 21, 2006 IFIP WCC 2006