SudokuSolver Forum

Recursion is when in a computer program a subroutine (procedure or function) directly or indirectly calls itself. Most brute force solvers for solving a sudoku uses recursion. It is guessing, i.e. in some sequence trying all "meaningful" possibilities. Varies cut-off techniques can be used to avoid trying possibilities, which will not yield a solution.
JSudoku uses DLX (Dancing Links) for "recursively solve". It is a "complicated", but fast and brilliant algorithm with very good cut-off.

AFAIK it is never executed automatically. You have to execute it manually (Ctrl+R)

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From my understanding of what is written about Full House and Last Digit in the JSudoku user guide, Naked Single catches Full House and Hidden Single catches both Full House and Last Digit.
Why Jean-Christophe decided to include them, probably only he can answer.

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When I selected "Deduce all moves" (my key bindings must be different from yours), here is what the solver gave me:



This is using your solver sequence on Ruud's Clueless Special #4a:

The jury is still out on that one!

The decision will likely be not to change the position of "Uniqueness Test 1", i.e. move it up to after "Fishy Cycle". This is the only position change needed to reflect the above quoted change to my rating table.
The main reason is that if "Uniqueness Test 1" is moved upwards it will be deployed earlier, and bring up the following window:


Mostly the check is fast, but with clueless puzzles it sometimes takes minutes, hours or even days and weeks, considerably slowing down puzzle generation.
And the less the puzzle is solved, the longer the check takes. The check is done by "recursively solve" using DLX.

Unless I am in the mood or feel for it, or it is time for a puzzle with Uniqueness Test(s), I disable all Uniqueness Test solvers. There are several upcoming (and hopefully interesting puzzles) with Uniqueness Test(s).

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AFIAK I use the default key bindings.

And with "Deduce all moves", either activated with Ctrl+Shift+D or through the Solve pulldown menu I get:

I have never seen a Recursive Solve unless I have explicitly activated it (Ctrl+R or Solve > Recursive Solve).
I do not have the faintest idea how this is activated or deactivated
I currently use Windows XP Professional, German localized.

Here are my General Preferences:

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Hmmm. . . it appears that accessing the Generator tab of the options (even without making any changes) wipes out most of the key bindings, at least on my system. Rather annoying, as I prefer to have "Generate grid at start" turned OFF.


I'm just as confused as you are. In any case, I STILL get the recursive solve whether I want it or not, just from "Deduce all moves". I do find it interesting that otherwise our technique lists are identical.


I'm using Windows XP Professional SP2, U.S. version.


And mine are identical.



I wish we could get hold of Jean-Christophe for some answers.

Have never experienced this. I also prefer to have "Generate grid at start" turned OFF.

I also have SP2, but I do not execute JSudoku from the local C drive, but from a network drive.
I work on the PC as an unprivileged user without any admin rights! Also installed JSudoku without admin rights. Admin rights are only allocated when absolutely necessary.
Java version: 1.6.0_01

Another forum member contacted me via a PM in February, asking if I new of any way to contact J-C. I found an e-mail address in a bonsai trees (very small trees) forum. I have just sent this forum member an express e-mail, asking if there was any success getting in contact with J-C.
Richard, our host surely has his email address. He has the email addresses of all the forum members.

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enxio27,
Please try the following: Past in Glyn Samurai #3A and do a "Deduce all moves".

This puzzle can only be completely solved using brute force, i.e. recursive solve.
So it would be interesting to know if a recursive solve is automatically included when you do a "Deduce all moves", or not.
If this puzzle is not solved completely by a "Deduce all moves", a recursive solve is not actually done, only listed.

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Which should I select when it asks about uniqueness solvers? I'm trying it now with "trust the grid designer", but it's clearly going to take a while.

ETA: I tried it all three ways, and it quickly got hung up. When I tried "recursively solve", it solved it almost immediately.

OK, now I feel as though I'm in the Twilight Zone. I retried the Clueless Special 4a (above), and now I get the same techniques listing that you do!



I wish I could remember now whether I invoked the recursive solver first before trying the "deduce all moves". I think I may have. I have since learned that JSudoku doesn't reset the solvers and other selections (for instance, uniqueness test) unless you repaste the puzzle code.