My Constraint Programming Blog

Survey of Paint-by-Number Puzzle Solvers by Jan Wolter has been updated. One interesting addition to the solver is a JaCoP solver: Ben Raziel's JaCoP Solver:

[from Ben Raziel:]
"""
We use JaCoP (a free java CSP solving library) to do the line solving for us. For searching, we use a modified version of JaCoP's DFS search. I employed your probing approach and tweaked it a little in order to achieve better performance.

The basic idea is to probe more cells, in order to reach a contradiction - which means we don't have to guess our next move (since a contradiction tells us what color the current cell is). The probes are ordered into "levels": each level contains cells where a contradiction is more likely to be found - which minimizes the number of cells that we have to probe until a contradiction is reached.
"""
The solver is not currently publically available, but the author plans to make it available, once this is cleared with the University.

From the summary of this solver

Assessment: Very good at hard puzzles, a bit slow at easy ones.

...

The run times on simple problems are not spectacular. Java is an interpreted language, and thus, naturally, rather slow. It is furthermore also built on top of a general solving library, JaCoP, and those typically add some overhead. But my suspicion is that part of this is also a basic design trade off - the authors were focusing more on solving hard puzzles fast than on solving easy puzzles fast.

But this really works very well on the harder puzzles. It solves every puzzle in the full 2,491 webpbn puzzle data set in under 15 minutes and only the "Lion" puzzle, which most solvers can't solve at all, takes more than 5 minutes. No other solver tested has accomplished this.

Of course, this solver, like pbnsolve, was trained on the webpbn data set, which certainly gives it an advantage when being tested against that data set. In fact the authors had the full dataset available from early in their development cycle, which is more than can be said for webpbn.

There are also other updates, such as general reflections about the state of Nonogram solvers.