Kraken Fish and Sashimi Fish

As we round the corner in our aquarium tour, the label on the n

The aquarium tour continues with two additional fish, and how ER/forcing chain “seeing” applies to them.

As we round the corner in our aquarium tour, the label on the next tank reads “Kraken X-wing”.  You may not be familiar with this label, but if you have been thinking about ways that candidates “see” each other, you were probably anticipating the fish.  We were noting that a victim of a finned fish remains a victim if it sees the fin, and you know a victim would not have to be in the fin box to  “see” the fin.

Kraken fish victimInspecting this fish, we see that the victim fin periscopes the fin with an ER wink, and IS TURNED TO STONE.  OK, I’ll calm down.  Anyway, it drops out. The candidate in Xr6c5, however,  is not a victim of the finned X-wing, because it does not see the fin. In fact, like most potential victims of finned fish, it escapes by forcing the fin to be true, not false.  We could note this by “Xr6c5 => fin”. If true, Xr6c5 not only takes a position, it forces the line to take the fin as a replacement. Kraken fish are not that mysterious.

Did you see the Empty Rectangle wink?  I normally spell it out as a grouped forcing chain. The kraken fish is a forcing chain extension of the finned fish, just as the iXYZ-wing is an extension of the XYZ-wing. You can bet there’s an iXY-chain out there, waiting for discovery, as well.

More later.

Right now, my head hurts, the feet are aching, and we’re ready for the cafeteria and gift shop.  We’ll have to come back. But hang in there for just one more stop. I want to show you the Sashimi X-wing they’ve got.

sashimi x-wingWe round the next corner and we’re looking at this strange little creature. Under the  Sashimi X-wing sign, we read something about not needing the corner candidate of the finned X-wing to make the removal.  Yeah, I can see that.  Also, I hear someone remark that the victim deserves it because he overreaches and wipes out two of the row candidates, leaving two rows with two candidates in the same position.

In the cafeteria over coffee, we get into some deep stuff about that last one:  What is the victim a victim of?  An imaginary finned X-wing?  Is a Sashimi an imaginary fish?  How are you going to recognize this thing?  Beats me, but there is something definitely familiar about those two slinks in the X-wing rows.   Wait, the Sashimi X-wing is a three legged X-chain.  That I’m sure I can recognize on an X-panel.

Now I’m wondering about some of the Sudoku lit I’ve read.  Could these fish actually be X-chains?  Remember, we’ve been burned before.  Looking back at the kraken  X-wing, the overlap with X-chains breaks down, because the fin makes one X-wing link weak.  Higher order exotics are not obligated to have slinks along the lines, so the mappings onto X-chains you sometimes see are special cases.

A multiple line fish that is almost perfect will stand out on an X-panel.  Too much for me on the full grid, but on an X-panel, I can do it. Another thing to mull over is that the Sashimi X-wing specimen we saw depended on a box wink.  We can wink in some tricky ways, can’t we?.

There’s much more to say about fish, including multiple fins. In the next posts, we take up the fundamentals of regular fish, and take advantage of the fact that subset economy and fish economy share the same mathematics.


About Sudent

My real name is John Welch. I'm a happily married, retired professor (computer engineering), timeshare traveling, marathon running father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. The blog is about Sudoku solving. It covers how to start, basic solving to find candidates efficiently, and advanced solving methods in an efficient order of battle. It is about human solving methods, not computer solving.
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2 Responses to Kraken Fish and Sashimi Fish

  1. Gerald Asp says:

    Regarding the LA Times puzzle of May 14, 2009, is there a ninth row to the puzzle? I am finally becoming familiar with fish techniques and am reviewing the March and April posts for 2012.

    • Sudent says:

      Hi Gerald,

      You deserve some kind of prize for being the first to comment on that missing row. It could be a blank south bank, but more likely its a typo. Anyway, the nest posts don’t follow up with a full grid, and my original copy was lost in a disk crash, so I updated that post and the previous one with a new example, replacing the whole segment. You can solve that one from the givens.

      In year 2012 I was short of examples, and now I have a lot more, from reviews. So it’s about time to update that year and add better graphics and links to many more examples. Thanks for the comment.


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