## ultimate fish and nishio

Advanced methods and approaches for solving Sudoku puzzles

### ultimate fish and nishio

I get what's going on with ultimate fish now! It still seems a bit like voodoo, how exactly you choose which sectors as a base and as a cover, maybe that's something that comes with experience. However it is a pattern based technique. Now some people disapprove of nishio, because it's not pattern based, so I was wondering if ultimate fish makes nishio redundant? Can anyone find a puzzle that solves with nishio, but not ultimate fish? Or can anyone explain why no such puzzle exists?
ab

Posts: 451
Joined: 06 September 2005

### Re: ultimate fish and nishio

ab wrote:Can anyone find a puzzle that solves with nishio, but not ultimate fish?

There are several posted here.
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

thanks ron! so i'm only a couple of months behind then
ab

Posts: 451
Joined: 06 September 2005

ronk: Your link prompted me to revisit the NoFish examples in the Broken Wing thread. Has anyone reviewed these recently to confirm that a template elimination occurs for which no (non-Kraken) fish can be found?

In the meantime, a Carcul approach.

Code: Select all
`# NoFish6# at least one of [r2c5],[r4c4],[r5c6] is <5># (missing explanation why)# this leads to [r6c5]<>5 because it 'sees' all three cells above*-----------------------------------*|  .  5  .  |  .  .  .  |  .  .  5  ||  5  .  .  |  . #5  .  |  5  .  .  ||  .  5  .  |  .  5  5  |  .  .  5  ||-----------+-----------+-----------||  5  .  .  | #5  .  .  |  .  .  5  ||  .  5  .  |  .  . #5  |  5  .  .  ||  5  .  .  |  . -5  .  |  5  .  .  ||-----------+-----------+-----------||  .  .  .  |  .  .  .  |  .  5  .  ||  .  .  5  |  .  .  .  |  .  .  .  ||  .  .  .  |  5  5  5  |  .  .  .  |*-----------------------------------*`
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

daj95376 wrote:Has anyone reviewed these recently to confirm that a template elimination occurs for which no (non-Kraken) fish can be found?

That's how these were identified, so I'm not sure what you mean.

daj95376 wrote:In the meantime, a Carcul approach.

Code: Select all
`# NoFish6# at least one of [r2c5],[r4c4],[r5c6] is <5># (missing explanation why)# this leads to [r6c5]<>5 because it 'sees' all three cells above*-----------------------------------*|  .  5  .  |  .  .  .  |  .  .  5  ||  5  .  .  |  . #5  .  |  5  .  .  ||  .  5  .  |  .  5  5  |  .  .  5  ||-----------+-----------+-----------||  5  .  .  | #5  .  .  |  .  .  5  ||  .  5  .  |  .  . #5  |  5  .  .  ||  5  .  .  |  . -5  .  |  5  .  .  ||-----------+-----------+-----------||  .  .  .  |  .  .  .  |  .  5  .  ||  .  .  5  |  .  .  .  |  .  .  .  ||  .  .  .  |  5  5  5  |  .  .  .  |*-----------------------------------*`

Would that "missing explanation" have anything to do with a skyscraper and x-wing leaving b2 without candidates?
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

ronk wrote:Would that "missing explanation" have anything to do with a skyscraper and x-wing leaving b2 without candidates?

I missed that 'explanation'. I saw a cannabalistic Jellyfish containing two Sashimi X-Wings that eliminate the two remaining cells in [r4].

Everyone works off the premise that the fish is true or else the fin cells are true. I say, what about the possibility of an invalid fish coupled with fin cells. This forces at least one the fin cells to be true!

FWIW: To the purists in the crowd, there's a Kraken Swordfish that'll perform the elimination. So, this NoFish puzzle does have a fish solution ... as do probably all of the other NoFish puzzles.
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

daj95376 wrote:Everyone works off the premise that the fish is true or else the fin cells are true. I say, what about the possibility of an invalid fish coupled with fin cells. This forces at least one the fin cells to be true!

I'd hesitate to call what I see an 'invalid fish.' Would you please illustrate and explain how you recognize it as invalid?

daj95376 wrote:To the purists in the crowd, there's a Kraken Swordfish that'll perform the elimination. So, this NoFish puzzle does have a fish solution ... as do probably all of the other NoFish puzzles.

I'm even more of a purist than that. To me, the elimination cells of a true fish are those elimination cells of the unfinned fish which also see all the fin cells directly. Therefore I view the so-called kraken fish as forcing chains that have a fish in the chain.
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

ronk wrote:I'd hesitate to call what I see an 'invalid fish.' Would you please illustrate and explain how you recognize it as invalid?

Code: Select all
`# original layout# Jellyfish r1245/c1279 w/fin cells [r2c5],[r4c4],[r5c6]*-----------------------------------*|  . *5  .  |  .  .  .  |  .  . *5  || *5  .  .  |  . #5  .  | *5  .  .  ||  .  5  .  |  .  5  5  |  .  .  5  ||-----------+-----------+-----------|| *5  .  .  | #5  .  .  |  .  . *5  ||  . *5  .  |  .  . #5  | *5  .  .  ||  5  .  .  |  .  5  .  |  5  .  .  ||-----------+-----------+-----------||  .  .  .  |  .  .  .  |  .  5  .  ||  .  .  5  |  .  .  .  |  .  .  .  ||  .  .  .  |  5  5  5  |  .  .  .  |*-----------------------------------*`

Code: Select all
`# layout wo/fin cells# Jellyfish contains ...# Sashimi X-Wing 'ab' => [r4c1]<>5 -and-# Sashimi X-Wing 'ac' => [r4c9]<>5 -thus-# Sashimi X-Wings cannibalize [r4] of Jellyfish => invalid state*-----------------------------------*|  . c5  .  |  .  .  .  |  .  . c5  || b5  .  .  |  .  .  .  | b5  .  .  ||  .  5  .  |  .  5  5  |  .  .  5  ||-----------+-----------+-----------|| -5  .  .  |  .  .  .  |  .  . -5  ||  . a5  .  |  .  .  .  | a5  .  .  ||  5  .  .  |  .  5  .  |  5  .  .  ||-----------+-----------+-----------||  .  .  .  |  .  .  .  |  .  5  .  ||  .  .  5  |  .  .  .  |  .  .  .  ||  .  .  .  |  5  5  5  |  .  .  .  |*-----------------------------------*`

The irony in this is that the (invalid) Jellyfish doesn't have to 'see' the elimination cell [r6c5].
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

### Invalid Jelly

Hello everybody, my first post here..
I like this (invalid) Jellyfish.

Code: Select all
`+-----------+-----------+   +-----------+-----------+|  .  .  .  |  .  .  .  |   |  .  .  .  |  .  .  .  ||  .  X  .  |  X  .  .  |   |  .  X  .  |  X  .  .  ||  .  .  X  |  .  X  .  |   |  .  .  X  |  .  X  .  |+-----------+-----------+   +-----------+-----------+|  .  X  .  |  X  .  .  |   |  .  .  X  |  .  X  .  ||  .  .  X  |  .  X  .  |   |  .  X  .  |  X  .  .  ||  .  .  .  |  .  .  .  |   |  .  .  .  |  .  .  .  |+-----------+-----------+   +-----------+-----------+`

I do not know how you guys call a tilted link in a box. Anyway, when the slope of it is the same in the 2 pairs of boxes, i.e. 1,2;3,4 or 1,3;2,4 the pattern is the well known double tier X-Wing or simply Jellyfish. Can you spot a Turbot there?

Code: Select all
`+-----------+-----------+|  .  .  .  |  .  .  .  ||  .  X  .  |  .  X  .  ||  .  .  X  |  X  .  .  |+-----------+-----------+|  .  X  .  |  X  .  .  ||  .  .  X  |  .  X  .  ||  .  .  .  |  .  .  .  |+-----------+-----------+`

But when the slope in one box is different from the other 3 ones, we get the invalid pattern.
I would rather call it "School of (perfect) Turbots". See how many they are?
Of cause since they are turbots, there should be some guardians somewhere there.

daj95376, who came up with this invalid Jelly?

Dan
DanG

Posts: 20
Joined: 28 March 2007

Interesting, daj95376.
At first I thought you were referring to Impossible Fish patterns where all candidates of a given number of base sectors can be covered with a smaller number of cover sectors. But this invalid fish reminds me more of a broken wing pattern. Actually I can identify several broken wings in the pattern of 5's, but each requires either r6c1 or r6c7 as an additional guardian outside of your Jellyfish. Nevertheless they also yield the exclusion r6c5<>5.

 I got it now. Your invald fish is based on the same closed loops of an odd number of strong links as my broken wings. You just don't give r6c1<>5 or r6c7<>5 explicitly as a premise but your premises r2c5<>5, r4c4<>5 and r5c6<>5 imply via the Jellyfish that r6c1<>5 and r6c7<>5 and this leads to the same invalid pattern.
So I guess using broken wings in the first place would be easier unless there's an example where the implied false guardians don't see the exclusion candidate.

Obi-Wahn

Posts: 63
Joined: 05 January 2007

### Re: Invalid Jelly

DanG wrote:
Code: Select all
`+-----------+-----------+|  .  .  .  |  .  .  .  ||  .  X  .  |  .  X  .  ||  .  .  X  |  X  .  .  |+-----------+-----------+|  .  X  .  |  X  .  .  ||  .  .  X  |  .  X  .  ||  .  .  .  |  .  .  .  |+-----------+-----------+`

But when the slope in one box is different from the other 3 ones, we get the invalid pattern.
I would rather call it "School of (perfect) Turbots". See how many they are?

Interesting point of view ... and there are eight turbot fish, of course, two for each diagonal. But in Obi-Wahn's NoFish6, only two of the eight turbot fish even have the possibility of yielding an exclusion -- the same exclusion r6c5<>5. For the other six, there is no cell that even sees all the guardians.
Code: Select all
` . *5  . |  .  .  . |  .  . *5        . *5  . |  .  .  . |  .  .  5*5  .  . |  .  5  . |  5  .  .       *5  .  . |  . @5  . | *5  .  . . @5  . |  .  5  5 |  .  . @5        . @5  . |  .  5  5 |  .  .  5---------+----------+----------      ---------+----------+----------*5  .  . | @5  .  . |  .  . *5        5  .  . |  5  .  . |  .  .  5 .  5  . |  .  .  5 |  5  .  .        . *5  . |  .  . @5 | *5  .  .@5  .  . |  .  5  . |  5  .  .        5  .  . |  .  5  . | @5  .  .---------+----------+----------      ---------+----------+---------- .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  5  5  5 |  .  .  .        .  .  . |  5  5  5 |  .  .  . Upper left diagonal (as turbot fish diagonal) . *5  . |  .  .  . |  .  . *5        .  5  . |  .  .  . |  .  . *5 5  .  . |  .  5  . | *5  .  .       *5  .  . |  . @5  . | *5  .  . . @5  . |  .  5  5 |  .  . @5        .  5  . |  .  5  5 |  .  . @5---------+----------+----------      ---------+----------+---------- 5  .  . |  5  .  . |  .  .  5       *5  .  . | @5  .  . |  .  . *5 . *5  . |  .  . @5 | *5  .  .        .  5  . |  .  .  5 |  5  .  . 5  .  . |  .  5  . | @5  .  .       @5  .  . |  .  5  . |  5  .  .---------+----------+----------      ---------+----------+---------- .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  5  5  5 |  .  .  .        .  .  . |  5  5  5 |  .  .  . Upper right diagonal . *5  . |  .  .  . |  .  . *5        .  5  . |  .  .  . |  .  .  5 5  .  . |  .  5  . |  5  .  .       *5  .  . |  . @5  . | *5  .  . . @5  . |  .  5  5 |  .  . @5        .  5  . |  .  5  5 |  .  .  5---------+----------+----------      ---------+----------+----------*5  .  . | @5  .  . |  .  . *5       *5  .  . |  5  .  . |  .  .  5 . *5  . |  .  .  5 |  5  .  .        . *5  . |  .  . @5 | *5  .  .@5  .  . |  .  5  . |  5  .  .       @5  .  . |  . -5  . | @5  .  .---------+----------+----------      ---------+----------+---------- .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  5  5  5 |  .  .  .        .  .  . |  5  5  5 |  .  .  . Lower left diagonal . *5  . |  .  .  . |  .  . *5        .  5  . |  .  .  . |  .  .  5 5  .  . |  .  5  . |  5  .  .       *5  .  . |  . @5  . | *5  .  . . @5  . |  .  5  5 |  .  . @5        .  5  . |  .  5  5 |  .  .  5---------+----------+----------      ---------+----------+---------- 5  .  . |  5  .  . |  .  . *5       *5  .  . | @5  .  . |  .  . *5 . *5  . |  .  . @5 | *5  .  .        .  5  . |  .  .  5 | *5  .  . 5  .  . |  .  5  . | @5  .  .       @5  .  . |  . -5  . | @5  .  .---------+----------+----------      ---------+----------+---------- .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  .  .  . |  .  .  .        .  .  . |  .  .  . |  .  .  . .  .  . |  5  5  5 |  .  .  .        .  .  . |  5  5  5 |  .  .  . Lower right diagonal`

DanG wrote:daj95376, who came up with this invalid Jelly?

AFAIK it was daj95376.
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

### Re: Invalid Jelly

DanG wrote:daj95376, who came up with this invalid Jelly?

I stumbled upon the invalid Jellyfish pattern while randomly/manually examining Obi-Wahn's NoFish6 puzzle. Since I haven't studied Broken Wing patterns, I didn't have his arsenal of techniques to guide me.

I was looking for a Kraken fish that would easily render this pattern solvable. During one attempt, I put together the four rows in question, and noticed that there was a Jellyfish with three remote/exo cells that (each) 'see' the elimination cell. I remember thinking that it was 'too bad' the Jellyfish didn't 'see' the elimination cell as well. While checking to see if the Jellyfish would indirectly perform the elimination, I noticed its cannibalistic nature. I realized this wasn't right and thought it over before making a post here. I was expecting someone would explain how I'd missed something simple -- as is often my fate.

FWIW, there are several Kraken fish that will perform the elimination. This is my favorite.

Code: Select all
`[r4c9]=[r13c9]-[r2c7]=[r56c7][r5c2]=[r13c2]-[r2c1]=[r56c1][r4c1] and [r5c7] 'see' [r4c9] and [r5c2]# Kraken X-Wing c17/r26 w/ [r4c1],[r5c7]# [r4c1]|[r5c7] => !([r4c9],[r5c2]) => ([r13c9],[r13c2]) => !([r2c7],[r2c1]) => [r2c5] => ![r6c5]*-----------------------------------*|  .  5  .  |  .  .  .  |  .  .  5  || *5  .  .  |  . +5  .  | *5  .  .  ||  .  5  .  |  .  5  5  |  .  .  5  ||-----------+-----------+-----------|| #5  .  .  |  5  .  .  |  .  .  5  ||  .  5  .  |  .  .  5  | #5  .  .  || *5  .  .  |  . -5  .  | *5  .  .  ||-----------+-----------+-----------||  .  .  .  |  .  .  .  |  .  5  .  ||  .  .  5  |  .  .  .  |  .  .  .  ||  .  .  .  |  5  5  5  |  .  .  .  |*-----------------------------------*`

FWIW #2: There is a single Kraken Swordfish pattern in NoFish7 that performs the eliminations for <1> and <2>.
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

### Re: Invalid Jelly

would it be possible to post or reference full pm grids for the single value grids under discussion
I don't feel like coding for specialized fishy grids -- have others done that?
edit: thanks
gsf
2014 Supporter

Posts: 7306
Joined: 21 September 2005
Location: NJ USA

### Re: Invalid Jelly

gsf wrote:would it be possible to post or reference full pm grids for the single value grids under discussion

The original puzzles NoFish1 thru NoFish21 are here. Allow for possible replacement of NoFish2 and NoFish4.

For the most part, one can just load the puzzle and use Simple Sudoku to get to the "sticking point" where these "broken wings" occur.

I suspect you can emulate Simple Sudoku with your solver options. If so, I would appreciate knowing the solver options to do so.

TIA, Ron
ronk
2012 Supporter

Posts: 4764
Joined: 02 November 2005
Location: Southeastern USA

### Re: Invalid Jelly

ronk wrote:I suspect you can emulate Simple Sudoku with your solver options. If so, I would appreciate knowing the solver options to do so.

thanks for the puzzle pointers
and the constraint options to emulate simple sudoku is a good idea
but the sequence didn't jump out from angus' site
do we have the ss technique/method order anywhere?
gsf
2014 Supporter

Posts: 7306
Joined: 21 September 2005
Location: NJ USA

Next