The New Sudoku Players' Forum

[Luke]

I can find very little info on this technique. Can anyone post a basic explanation or some examples?

Thanks,
Luke in Ca

[re'born]

Luke,

Check out this thread which I believe is the starting point for finned sealife.

rep'nA

[Luke]

Rep,

Thanks for the link. I'm looking it over, but the nomenclature is killing me.

What does POM stand for?
What does (1..n) mean?
NxN??
2-0-2, 1-2-1??

Which brings me to a gripe. Nobody around here has ever addressed this but I can guarantee you many like me have shaken their heads and wondered.

Sometimes it would seem these threads are written by and for the coupla hundred (dozen?) gurus who are conversant in Sudoku techno-speak. Gosh, y'all go way back, dontcha? I know the inner circle around here primarily address one another and share a common basis. The many thousands of enthusiasts who happen by this forum might as well be landing on the moon. What about them (me)?

It's almost as if you blokes pride yourselves in being as insular as possible. The Holy Grail is being the next Sue de Coq and getting recognized for an advancement in the genre. The latest treatise is always presented like a master's thesis. When you're not too busy trying to impress one another is there not one among you who can dumb it down? Speak to the pedestrian Suduko enthusiast once in a while and this forum might find itself with a much broader base. Unless that's what you're trying to avoid.....

No insult intended..... I'm impressed already,

Luke in Ca

[Mike Barker]

Hi Luke. When I first started reading posts here I was in the same situation as you. I found several good solution guides and then started keeping a list of useful posts. When someone else asked the same questions you are I posted the summary at http://forum.enjoysudoku.com/viewtopic.php?p=21804#p21804 . The guides should go a long way to answer your questions and maybe the rest of the collection can help in the future. As far as helping, most people here seem to go out of their way to help, sometimes maybe going even too far (I kind of felt that some of the posts to finlip's recent ideas may have gone a little far off target), but its people trying to help. As far as being a little esoteric in some of our posts, mea culpa. Please look at it as enthusiasm and not eliteism. Remember, too, that many posts are the response to other posts and following the whole thread (or in the case of my latest post multiple threads on multiple forums) will help. And always feel free to ask questions - but be prepared for a dozen different responses!

[Myth Jellies]

Hey Luke,

Your criticism is noted. Assuming you know what a swordfish is....

Perhaps the easiest way to think of it is a finned swordfish is almost a swordfish. The only thing that is blocking the swordfish from being a swordfish are one or more extra candidates that are called the fin. When taken together, you have a situation where either the fin is true or the swordfish is true. Those candidates that can see the fin and are also removed by the potential swordfish, can be removed.

Maybe now the examples in the previous finned fish thread will make more sense. It would probably be a good idea to make the language in that opening post a little more accessable. If anyone has some suggestions in that vein, I'd be happy to consider them.

In that finned fish thread, I used swordfish in the generic sense of an NxN swordfish. A 2x2 swordfish is called an x-wing, a 3x3 swordfish is just a swordfish, a 4x4 swordfish is called a jellyfish. If you don't really know what these are, you should look them up first before you tackle the finned variety.

As for the Pattern Overlay Method (POM); it is a very advanced technique based on templating which is good for seeing the elemental building blocks of a puzzle and solving them. POM has the advantage of converting sudoku from a pattern oriented puzzle into an algebraic puzzle. It is quite laborious to employ though, and it is hard to show your solution path when you use it. Now, I mainly use it to see how other advanced methods affect the basic innards of a puzzle.

[unkx80]

Allow me to blatantly quote the following (from http://homepages.cwi.nl/~aeb/games/sudoku/solving20.html):

A finned N-fish with elimination * for a given digit d is a set of N rows together with a cell * not in one of these rows, such that, after removal of all cells that 'see' * (i.e., lie in the same row, column or box as *), the remaining cells in these N rows that have d as a candidate lie in N-1 columns. Since N digits d cannot lie in N-1 columns, it follows that the cell * cannot be d, and we can eliminate this candidate.

(Or the same with rows and columns interchanged.)

I think that this rule would be relatively easy to understand, and it is supplemented by an example on that page. I believe this covers also the "sashimi" version of the fish, if I understood "sashimi" correctly.

Hope this helps.

[Luke]

Thank you for all the helpful comments and links. The light is sputtering on.

Also..after reading my original post in the light of day, I must apologize for its snarky tone. I need to get up to speed, I guess.

Thanks again for helping me out.

Luke in Ca

[re'born]

Luke,

Your concerns are well noted. Let me give a partial defense of this site. Firstly, many of us on this forum have been 'studying' Sudoku for months or years. The knowledge has not always come easy and there are very few of the regulars who understand everything. Part of that is because of presentation, but mostly it is because many of the techniques are complicated. It was only a post today that finally helped me to understand the definition of a Frankenfish and that is a relatively old technique and I am a relatively old member. Some things just aren't easy or easy to explain.

Even so, there have been several attempts to write down coherent treatments of particular topics (e.g., see Harvard's thread on Strong Links and Jeff's thread on Nice Loops among several others). These are not perfect and still cause confusion, but it is certainly an attempt by the members of this board to make our ideas understood by anybody willing to put in the time to sit down with a pencil and think.

I'm sure that if you continue to frequent this site, you will find the members very willing to explain topics and to welcome you into our little community of people who spend a little too much time on this incredibly deep but fun hobby.

[ravel]

Hi Luke.

you are welcome, thanks for your criticism, really any feedback is desired here. Often we dont know, if people forgot to thank for the answer or did not understand it [added:]or were not interested in it.

But i am sure, that you will get better answers here than i got from the hotline, when my phone&internet were not working (and they get paid for it)

[claudiarabia]

Hi Luke.

you are welcome, thanks for your criticism, really any feedback is desired here. Often we dont know, if people forgot to thank for the answer or did not understand it [added:]or were not interested in it.

But i am sure, that you will get better answers here than i got from the hotline, when my phone&internet were not working (and they get paid for it)

I have a suggestion in this regard.
Couldn't be in this board an alphabetic register with all the sudoku-terms and the best definitions in the forum would be attached to this by link? So this would be a guideline for beginners and a lexicon for the others.

with best regards

Claudia

[claudiarabia]

Hi Luke.

you are welcome, thanks for your criticism, really any feedback is desired here. Often we dont know, if people forgot to thank for the answer or did not understand it [added:]or were not interested in it.

But i am sure, that you will get better answers here than i got from the hotline, when my phone&internet were not working (and they get paid for it)

Couldn't there be in the forum an alphabetic register with all the sudoku terms and the best treatises in the forum about them attached as a link to the terms? That would be a great help for beginners and a useful lexicon for the rest of us.

With best regards

Claudia

[Mike Barker]

The collection of solving techniques tries to do this except they are grouped by catagory rather than alphabetically. See http://forum.enjoysudoku.com/viewtopic.php?p=21804#p21804 . Of course comments regarding improvements are always appreciated. In addition it points to two good lexicons and a half dozen good solving guides.

[MCondron]

Sudopedia is also a great reference for most of the questions raised here. It so far has, generally, excellent coverage of all but the most esoteric topics. I have found it to be a great help.

www.sudopedia.org

[wapati]

Luke,

Your concerns are well noted. Let me give a partial defense of this site. Firstly, many of us on this forum have been 'studying' Sudoku for months or years. The knowledge has not always come easy and there are very few of the regulars who understand everything. Part of that is because of presentation, but mostly it is because many of the techniques are complicated. It was only a post today that finally helped me to understand the definition of a Frankenfish and that is a relatively old technique and I am a relatively old member. Some things just aren't easy or easy to explain..

Further, there are three main approaches to solving the harder puzzles.

I use fishy patterns and know little else.
Coloring is another method that solves pretty much the same level of difficulty.
Chains is the third main method and can probably solve any puzzle.

So, reading about all methods at once nearly triples what you need to learn.

Simple Sudoku is a great program to use to learn colouring.

Sudoku Explainer seems to mostly use chains to reveal hints.

Sokuko Cue is good for being able to spot specific patterns.


There are other very good programs for helping explain puzzles, I don't mean to suggest they are unworthy of your time. These I named are just the ones I know best. There is a "Solver Programs" thread here that will help you see what is available.