Automatically Generating and Solving Eternity II Style Puzzles

The Eternity II puzzle is an NP-complete problem. Prior researchers have generated data sets that are similar to the Eternity II problem. These data sets can be created in linear time, but this comes at the cost of easing the problem by introducing exploitable statistical features. The first contribution of this paper is a new method to generate data sets that are truly of Eternity II style. The second contribution is an Eternity II specific implementation of a constraint-satisfaction-problem style algorithm. Unlike most other published algorithms, this one has no form of look-ahead, filtering, forward checking, back jumping or k-consistency checks. Instead, it uses knowledge about the structure of the puzzle and the uniform distribution of edge colours. This approach is up to three orders of magnitude faster than previously published attempts.