gecode VS OptaPlanner

You will most likely need both smarter heuristics and better deductions for larger instances. As mentioned, I've seen well-engineered custom tight C++-solvers with decent heuristics and the normal deductions take >1 hour on some instances. Most cases I've tried can be solved reasonably quickly when using OR-Tools CP-SAT which uses constraint programming style lazy clause generation and custom MIP relaxations in a portfolio.

For a list of interesting instances to test, see this file: https://github.com/Gecode/gecode/blob/release/6.3.0/examples...

I should probably do some benchmarks on that with the standard MiniZinc solvers.

Adding to wavemode, the Sudoku example is a good starting point: https://github.com/Gecode/gecode/blob/master/examples/sudoku...

In the documentation (https://www.gecode.org/doc-latest/MPG.pdf) there are a lot of worked examples as well.

Sure, there are lots but I think it should be doable. Will probably try sometime. Easiest is to make a model that fixes the lengths of the words, and just run it for different word lengths.

As a comparison, see this model solving crosswords using constraint programming. https://github.com/Gecode/gecode/blob/develop/examples/cross...

The main idea is that one defines tests that post the propagator on an initial domain, and then adding a checker for ground instances if it is a solution. The testing infrastructure runs the propagator in simulated setting, making sure that non-solutions are pruned and that solutions are found. Here is an example for the sorted constraint: sorted.cpp

However, if you need to solve constraints etc., see: https://www.optaplanner.org/

Try looking for something built around Optaplanner - basically taking the end game of rostering and working backwards.

OptaPlanner takes some of the items tracked in tool like Odoo and creates plans based on them. I.E. how do you manage shifts while juggling multiple constraints (Jerry can only work weekends, Jeff can only work afternoons, Jim can work weekends but only on double time, etc.)

There is a library out there called Optaplanner that is designed for optimization of NP complete problems. It is hard to tell if that is exactly what this is, but I think you should be able to use this regardless.

Just stumbled upon https://www.optaplanner.org. Looks very interesting but also really overkill.

OptaPlanner - a generic scheduler.

OptaPlanner

I've never used it but it sounds like OptaPlanner may be a scheduler in the same vein?