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What's New
From sudokuwiki.com, the puzzle solver's site
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The book "The Logic of Sudoku" is now for sale in the shop, as are the Puzzle Packs.
Fixed the issues with PayPal.

1st May 2010 - Killer Solver fixed
There was a bug that prevented modified or newly entered Killer puzzles being sent to the solver when using Internet Explorer. Seems to work for me now, let me know if there are still problems. Clear your cache before reporting. Also fixed a bug that sometimes presented chains in the killer solver when it shouldn't have.

5th Apr 2010 - Sue-De-Coq documented
A bit overdue but the documentation for Sue-De-Coq has been completed.

13th Mar 2010 - Digit Forcing Chains

I have added an extension to Forcing Chains I am dubbing Digit Forcing Chains - since they act on a single digit. It considers the implications through chains of having a candidate turned ON and turned OFF. This is the simplest type of Forcing Chain.
10th Mar 2010 - Editing bugs fixed

Many thanks for the feedbacks, especially bug alerts. I was aware of candidate editing in Internet Explorer was buggy - it wouldn't redraw a cell when you exited the edit box. But the other solvers were worse. I've gone through all four solvers in IE and Firefox and fixed the editing so it is now clear and displays properly. As ever, please clear your cache before reporting a problem - 90% the time problems are caused by mixing old and new scripts.

7th Mar 2010 - Strategy docs updated
See
3D Medusa
Cell Forcing Chains
Unit Forcing Chains
Some strategies have been dropped from the solver and marked as depreciated in the documentation. These are Guardians, Multivalue X-Wing and BUG.

6th Mar 2010 - New Release of all Solvers!

I am pleased to be releasing a new version of the solvers (all four). This is the first of two installments. Today's release contains several several new strategies: 3d Medusa and a much more powerful set of Forcing Chains. 3D Medusa on a single number is identical to Simple Colouring. On more than one number it replaces Multi-Coloring - but the new implementation is more powerful.

My orginal Forcing Chains algorithm was very weak. I have completely re-written it to look at Dual, Triple and Quad Forcing chains both in a single cell (2, 3 or 4 candidates in a cell) and across a unit (2, 3 or 4 of X in a unit). Both these strategies are in the process of documentation. The success rate of these strategies is very high so I have also had to recalibrate my grader.

I have replaced all the example puzzles in the Sudoku solver and expanded the list. This should help anyone interested in finding an example.

I am moving away from the formal terms "strong (=)" and "weak (-)" links in favour of + and - symbols indicating a candidate is presumed to be ON or OFF - which I am now colouring on the board in green and red. This applies to all chaining strategies. This will I hope make the contraditions and eliminations much clearer and explanatory. I have a great deal of documentation to update because of these change.

The second part of the release will be a re-design of the way the solver returns solutions. What I want to provide is a list of the best (easiest) eliminations at any one stage. This will apply to diabolical strategies and above. This will be the first time we will be able to look breath-wise across the solution space - rather than depth-wise as at the moment. Currently the solver returns the first elimination of a sucessful strategy. The reason for this was speed. The new version, I hope, will return a list of results from which preferences can be chosen and sorted. This will allow anyone to move through the solution using techniques they are most confortable with. It will also allow us to better understand a difficult problem when different solution can be looked at each stage.

Enjoy
25th Jan 2010 - Vastly superior Chaining illustrations on solver

I'm very pleased with a new graphical element I've added to Chaining strategies. Where chains are used the Sudoku solver will now draw those chains on the board. Previously I could only highlight the cells which were part of the chain but this was difficult to follow. Now Strong and Weak links are plotted between candidates. The new illustrations can also plot grouped ALS cells, as in the example to the right.

This example, from sudoku.com.au, has numerous instances of chaining strategies and tests the new illustrations very well - try loading this puzzle and stepping through.

Key

I am using a very simple but effective javascript library by Walter Zorn (www.walterzorn.com). 		Example of the new Chaining illustrations
Example of the new Chaining illustrations: From the Start
24th Jan 2010 - New strategy added

Hidden Unique Rectangles have been expanded to include the new Type 2B.
26th Sep 2009 - New Daily Puzzle available

I've added a new Daily Str8ts puzzle at www.str8ts.com - an asymmetrical version of Str8ts. Really just to explore the fun of a board with less symmetry. Enjoy.
4th Sep 2009 - Str8ts Lite available on the iPhone

I'm very pleased to announce the release of the FREE version of Str8ts, a 20 game version of the fun 6x6 Str8ts game. More information here. This compliments the 9x9 Str8ts game already available on iTunes. Enjoy :)
27th Aug 2009 - Load Daily Sudoku into Solver

Had a number of requests for this, so I have added a button to allow you to load the Daily Sudoku into the solver, either if you are stuck or if you wish to print the puzzle with the candidates show.
17th Aug 2009 - Perfect 3-3-3 SwordFish

Klaus Brenner has found a lovely 3-3-3 Swordfish. You can view and load it from the end of the Sword-Fish page.
17th Aug 2009 - Brain Stretcher!

David Filmer has passed onto me a crackingly difficult Sudoku puzzle he has made himself. You can
load this puzzle into the solver.
14th Aug 2009 - KenKen and KenDoku solvers released!

These are beta (for testing and evaluation) - I can't claim they are entirely bug free or are perfectly complete for all cage combinations, but I've tested quite a few. Do enjoy and let me know if you can see any improvements. Links in main menu. I have been commissioned by the folks at www.kenken.com to create these solvers and I hope to see a version of them on their web site soon.

Keeping a track of changes on this page starting from mid August 2009
24th March 2009 -
Read my response to J.F.Crook's paper "A Pencil-and-Paper Algorithm for Solving Sudoku Puzzles.

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Comments...

Monday 15-Feb-2010

... by: Dale Kloss

RE: 17th Aug 2009 -the Brain Stretcher!

Never mind- I found it. The color difference (on this computer monitor) wasn't enough to be readily visible. Dale

Monday 15-Feb-2010

... by: Dale Kloss

RE: 17th Aug 2009 -the Brain Stretcher!

Where's it at? I did a casual look around & didn't see it. Thanks for all the work on the site. Dale Kloss

Thursday 11-Feb-2010

... by: DALE KLOSS

When are you going to document Bowman's Bingo & Nishio ?

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Article created on 17-August-2009. Views: 6559
This page was last modified on 1-May-2010, at 11:11.
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Copyright Andrew Stuart @ Scanraid Ltd, 2010