Feedback and Questions

There may be a tiny number of puzzles which are unsolvable using the strategies/implementation I have in my solver after you turn off UR strategies. I'd have to run quite a large test suit to know for sure. But I don’t know every possible logical strategy yet - no one does, so its impossible to state what % are true for your statement. But usually there are several ways to kin the cat at any one stage. Any strategy, unless it is wholly a sub-set of another - will increase the hit rate, even if only by a tiny amount

I'll go with that typo suggestion, makes more sense.
Grouped X-Cycles includes all X-Cycles so yes if you turn the first off then a normal X-Cycle will turn up in the grouped one. I suppose I could filter them but what I am doing is performing a search with additional flags (yes to grouped cells and other types of links) rather than negatively filtering the first. Grouped X-Cycles is a super set of X-Cycles

Very glad you like, thanks for the feedback!

This is a very good observation, and I think you have to be a programmer trying to build the algorithm to spot this, so congrats. I'm certain Rules 4 came a long first and then - much later - further eliminations were spotted that Rule 4 failed to get and led to rule 5. What didn’t happen was a consideration that this rules was a super-set of another. Anyway, I've taken a couple of examples with plenty of instances of Simple Colouring and 3D Medusa and satisfied myself that Rules 5 does get all rules 4 instances plus it's addition ones.

LOAD PUZZLE
This one had 2x Rules 4 and 2x Rules 5 3D Medusas, but I'm patching the solver tonight, so you wont see them unless yr quick. It now shortens the solution path.

LOAD PUZZLE
This puzzle has many Simple Colorings - only the last right at the end does the new rule get two 4s instead of one.

Basically, all I need to do is remove the code for Rule 4 and let Rule 5 do the job. That's awkward because I now have to rename Rule 5 to Rule 4 and Rule 6 to Rule 5. Can't have a gap in the sequence. I'll try to update the documentation on Simple Colouring and 3D Medusa at the same time.

I'd be delighted to credit you on the pages.

It's rare to find a simplification, it's normally the case I have to add a complication

Yes, there are usually several examples of strategy X at any one point, and it depends on the search order. I'm sure you are going top left to bottom right and 1 to 9, which seems natural, but from then on it really depends on your pattern identifier. For chains I create a list of all possible chains and rank them according to "best", which is a set of rules about how long the chains are, how many eliminations they make, if they give a single cell solution, if they contain awkward links like grouped cells or ALSs. So there is a lot in the air and no two solvers will match.

Ideally I'd like to give the user an option to scroll through all the instances of a given strategy but it would greatly complicate the UI.

A very pretty Medusa! Nice catch

A single instance of a hard strategy does not a hard puzzle make. These are two different spectrums. It is possible to make trivial puzzles with a single very hard step (a bottleneck) and I try and filter those out when selecting for publishing, as they don’t make good puzzles. They are useful as exemplars, eg see X-Wings


Do let me know what puzzle it was, if you can find it again, I'd be happy to take a look at it.

For a fuller idea of how grading works, take a look at this write up.

There is some demand for that, and I do make those puzzles, but not quite enough yet to make a solver. On my wish list as well

Thanks Debo.
Will be ten years old in May. Had a lot of helpful comments aloing the way, and much encouragement

If you are talking about the Sudoku Solver for Android, go to settings and change the choice for "how long to keep".
On favourites - long click will offer a delete

Best regards