The Ultimate FISH Guide

Advanced methods and approaches for solving Sudoku puzzles

Postby daj95376 » Mon Feb 04, 2008 9:35 am

A Hidden Single is not a single 1-Fish. At best, it's a Siamese 1-Fish. An example:

Code: Select all
 Hidden Single   -or-
 Siamese 1-Fish r5\c5|b5     1-Fish r5\c5                1-Fish r5\b5
 +-----------------------+   +-----------------------+   +-----------------------+
 | . . . | . * . | . . . |   | . . . | . * . | . . . |   | . . . | . . . | . . . |
 | . . . | . * . | . . . |   | . . . | . * . | . . . |   | . . . | . . . | . . . |
 | . . . | . * . | . . . |   | . . . | . * . | . . . |   | . . . | . . . | . . . |
 |-------+-------+-------|   |-------+-------+-------|   |-------+-------+-------|
 | . . . | * * * | . . . |   | . . . | . * . | . . . |   | . . . | * * * | . . . |
 | / / / | / X / | / / / |   | / / / | / X / | / / / |   | / / / | / X / | / / / |
 | . . . | * * * | . . . |   | . . . | . * . | . . . |   | . . . | * * * | . . . |
 |-------+-------+-------|   |-------+-------+-------|   |-------+-------+-------|
 | . . . | . * . | . . . |   | . . . | . * . | . . . |   | . . . | . . . | . . . |
 | . . . | . * . | . . . |   | . . . | . * . | . . . |   | . . . | . . . | . . . |
 | . . . | . * . | . . . |   | . . . | . * . | . . . |   | . . . | . . . | . . . |
 +-----------------------+   +-----------------------+   +-----------------------+
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Postby Pat » Mon Feb 04, 2008 12:56 pm

Mike Barker wrote:to me, sashimi is just a type of finned fish. Its importance is only to make clear to fisherpeople that a fin can exist even without a cell which is part of the main fish.

The definition that a sashimi fish degenerates when the fin is removed is a valid technical distinction, but doesn't differentiate three classes of fish, that is, unfinned, finned and sashimi. I only see two, finned and unfinned.


yes, i agree entirely.

rkral (2007.Dec.6) wrote:
AFAIK common usage for quite some time has been ...
    finned -- meaning finned non-sashimi
    sashimi -- meaning (finned) sashimi
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Postby daj95376 » Thu Feb 07, 2008 8:06 am

Does anyone remember my puzzle #B147 ?

Here's an excerpt from it where a mutant Swordfish contains an example of a fully-grouped single-digit chain starting at [r2c9] and ending at [r2c5]; i.e., X-Colors.

Code: Select all
+--------------------------------------------------------------------+
|  1      47     34    |  8      5      3679  |  369    69     2     |
|  9      35     8     |  234    34     236   |  7      1      356   |
|  357    6      2     |  379    1      379   |  359    4      8     |
|----------------------+----------------------+----------------------|
|  235    35     7     |  24     349    1     |  8      269    369   |
|  4      9      6     |  237    8      237   |  23     5      1     |
|  23     8      1     |  6      39     5     |  4      2379   379   |
|----------------------+----------------------+----------------------|
|  6      47     345   |  1359   2      39    |  159    8      3579  |
|  37     2      9     |  15     6      8     |  15     37     4     |
|  8      1      35    |  359    7      4     |  2569   2369   3569  |
+--------------------------------------------------------------------+

Code: Select all
3-Fish r5c5b3\r2c7b5   <> 3  [r2c246]
+-----------------------------------+
|  .  .  3  |  .  .  3  | G3  .  .  |
|  . -3  .  | -3 G3 -3  |  .  . B3  |
|  3  .  .  |  3  .  3  | G3  .  .  |
|-----------+-----------+-----------|
|  3  3  .  |  . B3  .  |  .  .  3  |
|  .  .  .  | G3  . G3  | B3  .  .  |
|  3  .  .  |  . B3  .  |  .  3  3  |
|-----------+-----------+-----------|
|  .  .  3  |  3  .  3  |  .  .  3  |
|  3  .  .  |  .  .  .  |  .  3  .  |
|  .  .  3  |  3  .  .  |  .  3  3  |
+-----------------------------------+

While looking at unfinned Franken fish, I noticed that all of my examples contain at least one unfinned mutant fish of the same size that performs identical eliminations. I'm not really surprised by this, but I would like to know if anyone is aware of this relationship always being true.
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Postby Pat » Thu Feb 07, 2008 1:04 pm

daj95376 wrote:While looking at (unfinned) Franken fish,
I noticed that all of my examples contain at least one (unfinned) Mutant fish of the same size
that performs identical eliminations.

I'm not really surprised by this, but I would like to know if anyone is aware of this relationship always being true.


early on, we saw that each Franken Swordfish and Jellyfish
has an equivalent Mutant of the same order
    later, Obi-Wahn (2007.Jan.22) explained about equivalent fish

    with his transformations,
    i expect that the answer to your question is:
    yes the relationship must be always true.

    (without proof)
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Postby tarek » Sat Feb 09, 2008 4:43 pm

Regrding sashimi,

I know that almost evrybody uses it to describe a form of finned fish.

As it stands, I am against this. I'm hoping to change this way of describing fish so that sashimi (even if this would be redundant) is used as a different adjective. This in my opinion would not contradict any work done on the subject until now. furthermore it would make using the term more formalised especially when introducing concepts like the unfinned sashimi fish.

If my attempts do not work, then this is just to confirm to all sashimi haters out there that I really really tried:(

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Postby ronk » Sat Feb 09, 2008 10:03 pm

tarek wrote:I'm hoping to change this way of describing fish so that sashimi (even if this would be redundant) is used as a different adjective.

So instead of 1) unfinned, 2) finned and 3) sashimi ... we would have 1) non-sashimi unfinned, 2) non-sashimi finned and 3) sashimi finned:?:

You can always write the definitions that way. If it catches on, it catches on ... if it doesn't, it doesn't. For my part, I would probably just omit the "sashiminess adjective." It's absolutely the last detail I look at when describing a fish anyway.

Unfortunately, that approach doesn't work when generating exemplars. It's the sashimi property that determines whether or not the fin cell(s) can be removed.
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Postby tarek » Sat Feb 09, 2008 10:54 pm

yes that is what I was trying to get to.........

As it doesn't conradic what we have at the moment, then formalising it as seperate adjective would be best.

on most occasions it can be dropped. when it is used however, I am hoping that people would specify "finned" in addition to it.

I hope it will take off...

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Postby daj95376 » Sat Feb 09, 2008 11:10 pm

ronk: four types -- excluding the basic qualifier

Code: Select all
1) non-sashimi unfinned fish
2)     sashimi unfinned fish
3) non-sashimi   finned fish
4)     sashimi   finned fish

tarek: sashimi unfinned fish ???

I guess the question for me is whether or not I'd ever encounter a sashimi unfinned fish with the technique hierarchy I use in my solver.

I have 275 canonicalized hidden patterns that aren't in ronk's exemplars dated Oct 24, 2007. Of these, my solver would never report the following entries as sashimi unfinned fish.

Code: Select all
   5   non-degenerate; i.e., non-sashimi
 227   degenerate through an initial Hidden Single or Locked Candidate (1/2)
  18   degenerate through an initial X-Wing
   5   degenerate through an initial Swordfish
   4   degenerate through an initial Jellyfish
----
 259   never reported

 275   HPc14n
-259   never reported
----
  16   possible ... that I'm currently reviewing

I'll update this message once I've finished reviewing these 16 entries.
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Postby ronk » Sat Feb 09, 2008 11:18 pm

daj95376 wrote:ronk: four types -- excluding the basic qualifier

Code: Select all
1) non-sashimi unfinned fish
2)     sashimi unfinned fish
3) non-sashimi   finned fish
4)     sashimi   finned fish

An "unfinned sashimi" wasn't a fish. Change "sashimi" from a noun to an adjective and "sashimi unfinned fish" still does not a fish make. And I've pretty much run out of different ways to say that.:)
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Postby tarek » Sat Feb 09, 2008 11:23 pm

daj95376 wrote:ronk: four types -- excluding the basic qualifier

Code: Select all
1) non-sashimi unfinned fish
2)     sashimi unfinned fish
3) non-sashimi   finned fish
4)     sashimi   finned fish
Correct
daj95376 wrote:tarek: sashimi unfinned fish ???

I guess the question for me is whether or not I'd ever encounter a sashimi unfinned fish with the technique hierarchy I use in my solver.
Well you SHOULDN'T encounter them. The only ways would be:
1. if there is some strange technique heirarchy in an electronic solver
2. a manual solver failing to spot THE SMALLER fish
3. coding errors in electronic solvers.
4. intentional.

At this stage there are some conflicting opinions about whether to allow this "sashimi unfinned" creature to be named as such, whoever is going to present it must have a reason for it (it will be one of the 4 above)

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Postby daj95376 » Sun Feb 10, 2008 2:50 am

tarek wrote:
daj95376 wrote:tarek: sashimi unfinned fish ???

I guess the question for me is whether or not I'd ever encounter a sashimi unfinned fish with the technique hierarchy I use in my solver.

Well you SHOULDN'T encounter them. The only ways would be:
1. if there is some strange technique heirarchy in an electronic solver
2. a manual solver failing to spot THE SMALLER fish
3. coding errors in electronic solvers.
4. intentional.

Actually, I just realized that I encounter sashimi unfinned fish all of the time. The trick sometimes is knowing that they are Sashimi.

Code: Select all
  Sashimi finned mutant Jellyfish r39c5b6\r6c7b27   for [r8c2]<>X
  +-----------------------------------+
  |  .  .  .  |  *  X  *  |  *  .  .  |
  |  .  .  .  |  *  X  *  |  *  .  .  |
  |  /  #  /  |  X  /  X  |  X  /  /  |
  |-----------+-----------+-----------|
  |  .  .  .  |  .  /  .  |  X  /  /  |
  |  .  .  .  |  .  /  .  |  X  /  /  |
  |  *  *  *  |  *  X  *  |  *  X  X  |
  |-----------+-----------+-----------|
  |  *  *  *  |  .  /  .  |  *  .  .  |
  |  * **  *  |  .  #  .  |  *  .  .  |
  |  X  X  X  |  /  /  /  |  X  /  /  |
  +-----------------------------------+

Based on ...

Code: Select all
  Sashimi unfinned mutant Jellyfish r39c5b6\r6c7b27
  +-----------------------------------+
  |  .  .  .  | **  X **  | **  .  .  |
  |  .  .  .  | **  X **  | **  .  .  |
  |  /  /  /  |  X  /  X  |  X  /  /  |
  |-----------+-----------+-----------|
  |  .  .  .  |  .  /  .  |  X  /  /  |
  |  .  .  .  |  .  /  .  |  X  /  /  |
  | ** ** **  | **  X **  | **  X  X  |
  |-----------+-----------+-----------|
  | ** ** **  |  .  /  .  | **  .  .  |
  | ** ** **  |  .  /  .  | **  .  .  |
  |  X  X  X  |  /  /  /  |  X  /  /  |
  +-----------------------------------+

Yes, I realize that this isn't the same thing as running directly into a sashimi unfinned fish in a PM. But, I do encounter them none the less.
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Postby Mike Barker » Sun Feb 10, 2008 5:27 am

To me the "unfinned sashimi Jellyfish" is a Mutant Swordfish:
Code: Select all
Mutant Swordfish r3c5b6/r6c7b2
  +-----------------------------------+
  |  .  .  .  | **  X **  | **  .  .  |
  |  .  .  .  | **  X **  | **  .  .  |
  |  /  /  /  |  X  /  X  |  X  /  /  |
  |-----------+-----------+-----------|
  |  .  .  .  |  .  /  .  |  X  /  /  |
  |  .  .  .  |  .  /  .  |  X  /  /  |
  | ** ** **  | **  X **  | **  X  X  |
  |-----------+-----------+-----------|
  |  .  .  .  |  .  /  .  | **  .  .  |
  |  .  .  .  |  .  /  .  | **  .  .  |
  |  .  .  .  |  .  /  .  | **  .  .  |
  +-----------------------------------+

Which allows an elimination in r9c7 leaving a locked candidate in b7.
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Postby daj95376 » Sun Feb 10, 2008 7:41 am

Mike Barker wrote:To me the "unfinned sashimi Jellyfish" is a Mutant Swordfish:
Which allows an elimination in r9c7 leaving a locked candidate in b7.

Yes, here's how I approached it.

1) finned mutant Jellyfish based on ...
2) unfinned mutant Jellyfish that's discovered to ...
3) degenerate through unfinned mutant Swordfish, so ...
4) Sashimi adjective appended to beginning of (1) and (2).
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Postby Mike Barker » Sun Feb 10, 2008 2:11 pm

I guess I see it differently. We agree that by definition a Sashimi fish degenerates when the fin is removed. From my POV it is now two or more smaller fish and it would be appropriate to refer to it as such. To me keeping the larger degenerative fish misses the point. Also to me the "Sashimi" adjective is a way to convey the idea that in looking for finned fish one has to look for cases where the fish is missing a node at the fin. The degenerative characteristic is a mathematical way of describing the situation. Applying it to non-finned fish seems to weaken the message, but Tarek has been right many times before and others may prefer defining fantasy fish. If this helps others that's great.
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Postby ronk » Sun Feb 10, 2008 2:21 pm

I don't think a "sashimi finned" fish should ever be illustrated without a fin cell. Removal of the fin cells is a "what if" condition, an imaginary condition ... that we're all very capable of imagining.

Indeed, I think the very concept of "sashimi unfinned" N-fish still being an N-fish after fin removal is ludicrous.

BTW daj95376, you've misused the double asterisk "**" symbol in your "sashimi unfinned" illustration ... and now Mike has done it too.
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