XCSP3: An Integrated Format for Benchmarking Combinatorial Constrained Problems
This work addresses the problem of benchmarking and comparing algorithms for combinatorial constrained problems in the constraint programming community, though it is incremental as it builds on an existing format.
The authors tackled the need for a standardized format to represent combinatorial constrained problems by proposing XCSP3, a major revision of XCSP 2.1 that integrates various problem types and constraints, resulting in a compact, readable format that encompasses practically all constraints from major constraint solvers.
We propose a major revision of the format XCSP 2.1, called XCSP3, to build integrated representations of combinatorial constrained problems. This new format is able to deal with mono/multi optimization, many types of variables, cost functions, reification, views, annotations, variable quantification, distributed, probabilistic and qualitative reasoning. The new format is made compact, highly readable, and rather easy to parse. Interestingly, it captures the structure of the problem models, through the possibilities of declaring arrays of variables, and identifying syntactic and semantic groups of constraints. The number of constraints is kept under control by introducing a limited set of basic constraint forms, and producing almost automatically some of their variations through lifting, restriction, sliding, logical combination and relaxation mechanisms. As a result, XCSP3 encompasses practically all constraints that can be found in major constraint solvers developed by the CP community. A website, which is developed conjointly with the format, contains many models and series of instances. The user can make sophisticated queries for selecting instances from very precise criteria. The objective of XCSP3 is to ease the effort required to test and compare different algorithms by providing a common test-bed of combinatorial constrained instances.