Automatically improving constraint models in Savile Row
Date
10/2017Author
Grant ID
EP/H004092/1
EP/K015745/1
EP/M003728/1
UF1204070
Keywords
Metadata
Show full item recordAbstract
When solving a combinatorial problem using Constraint Programming (CP) or Satisfiability (SAT), modelling and formulation are vital and difficult tasks. Even an expert human may explore many alternatives in modelling a single problem. We make a number of contributions in the automated modelling and reformulation of constraint models. We study a range of automated reformulation techniques, finding combinations of techniques which perform particularly well together. We introduce and describe in detail a new algorithm, X-CSE, to perform Associative-Commutative Common Subexpression Elimination (AC-CSE) in constraint problems, significantly improving existing CSE techniques for associative and commutative operators such as +. We demonstrate that these reformulation techniques can be integrated in a single automated constraint modelling tool, called Savile Row, whose architecture we describe. We use Savile Row as an experimental testbed to evaluate each reformulation on a set of 50 problem classes, with 596 instances in total. Our recommended reformulations are well worthwhile even including overheads, especially on harder instances where solver time dominates. With a SAT solver we observed a geometric mean of 2.15 times speedup compared to a straightforward tailored model without recommended reformulations. Using a CP solver, we obtained a geometric mean of 5.96 times speedup for instances taking over 10 seconds to solve.
Citation
Nightingale , P , Akgün , Ö , Gent , I P , Jefferson , C , Miguel , I & Spracklen , P 2017 , ' Automatically improving constraint models in Savile Row ' , Artificial Intelligence , vol. 251 , pp. 35-61 . https://doi.org/10.1016/j.artint.2017.07.001
Publication
Artificial Intelligence
Status
Peer reviewed
ISSN
0004-3702Type
Journal article
Description
Authors thank the EPSRC for funding this work through grants EP/H004092/1, EP/K015745/1, EP/M003728/1, and EP/P015638/1. In addition, Dr Jefferson is funded by a Royal Society University Research Fellowship.Collections
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