ATHANOR:
High-Level Local Search Over Abstract Constraint Specifications in ESSENCE
Abstract
This paper presents ATHANOR, a novel local search
solver that operates on abstract constraint specifi-
cations of combinatorial problems in the ESSENCE
language. It is unique in that it operates directly on
the high level, nested types in ESSENCE, such as set
of partitions or multiset of sequences, without refining such types into low level representations. This
approach has two main advantages. First, the structure present in the high level types allows high quality neighbourhoods for local search to be automatically derived. Second, it allows ATHANOR to scale
much better than solvers that operate on the equivalent, but much larger, low-level representations.
The paper details how ATHANOR operates, covering incremental evaluation, dynamic unrolling
of quantified expressions and neighbourhood construction. A series of case studies show the performance of ATHANOR, benchmarked against several
local search solvers on a range of problem classes