From Sudopedia, the free Sudoku reference guide

From Sudopedia

There is a terminology problem here which was brought to my attention by the folks on the Sudocue forum. The problem is that this technique ought properly to be called "Naked Killer Subsets" because it's essentially an expansion of the Naked Subset technique from ordinary sudoku. (For instance, the first example is essentially a killer version of a naked {12} pair occurring in the same house in regular sudoku.) See discussion here.

That said, I think it would be a mistake to rename this "Naked Killer Subsets" because that is a counter-intuitive name: the subsets are often (as in my example #2 here with the quint) very deeply buried!

So perhaps we need a fresh term here. Either a different pair from Naked/Hidden needs to be thought up, or just a general catch-all term for the technique. Thoughts, anyone? --Nd

Hello Nd,

Thanks for opening up this discussion. I think I may have a solution here, which does not break with tradition and should keep most people happy.

Firstly, I agree with you that both variants of this technique are not particularly obvious, and thus don't really warrant the term "naked". At the same time, like you say, we need to be able to distinguish between the two cases, if the need arises. Without resorting to anonymous qualifiers as for Unique Rectangles, such as "Type 1" and "Type 2", I would thus like to suggest the following:

1) "Hidden Killer Subset" (or simply "Killer Subset"), if we do not want to distinguish between the two variants (e.g., for your article heading).

2) "Killer Naked Subset" and "Killer Hidden Subset" to refer to the two variants explicitly. The posiitoning of the words changes the interpretation significantly. For example, "Killer Naked Subset" simply implies that it's the Killer variant of the regular "Naked Subset" technique. This nomenclature is also compatible with that already used by J-C Godart, as used here.

3) "Killer Subset", as shorthand for the more obvious and commonly-encountered "Killer Naked Subset". This is compatible with the usual meaning of the term "Killer Pair" found in walkthroughs. This term can also be used by programs that only support one of the two variants, and thus where no further clarification is required.

Does this sound reasonable to you?

Mike

Mike: hm, will think. I think that it's asking for trouble to have "Hidden Killer Subset" and "Killer Hidden Subset" mean different things, though! Can't imagine that that distinction would stick.... -- Anyone else have thoughts on this? --Nd 03:34, 12 February 2007 (CET)

Nd,

Yes, I agree with you that it would be rather nice to get a few other opinions on this. "Hello, hello, is anybody out there?" (Note the hidden (or maybe "naked"?!) reference to Pink Floyd "The Wall" there). If so, please contribute if you feel you can!

As to your objection, I'm not so convinced that we even need the term "Hidden Killer Subset". Like you've said before, both types are essentially hidden, making this qualifier superfluous. So as far as I'm concerned, your article could simply be renamed to "Killer Subset" and then go on to to mention the two specific types, "Killer Naked Subset" and "Killer Hidden Subset", without mentioning the term "Hidden Killer Subset" at all. Surely,it's only worth prefixing a technique with the qualifier "Hidden" if there's a complementary "Naked" technique.

By the way, on that note, I would also have nothing against the specific terms "Naked/Hidden Killer Subset", either. In fact, I find that they read better than "Killer Naked/Hidden Subset". And even though the naked variant is not particularly "naked" (in the sense of "obvious"), relative to the hidden variant it is. Indeed, it's hard enough finding a Hidden Quad in regular Sudoku, even if one has been given the hint that there *is* one somewhere (!), so finding a genuine Killer variant (that's not "just" based on consecutive digits at the beginning or end of the value range) would probably be almost impossible for a human solver to find. On the other hand, the "naked" variant is indeed significantly easier to spot. This can easily be proved by reading through the various walktroughs on the web. Although the "naked" and "hidden" variants always exist simultaneously, and thus occur equally often, in practice nearly every reference to a "killer pair" refers to the naked variant. Wouldn't it therefore by great if we could keep this concise and convenient shorthand for this common case, and only refer the longer forms when the context requires it, or when we need to refer to the less commonly-used "hidden" variant?

Mike -- Mhparker

How about "Naked Subset (Killer)", "Hidden Subset (Killer)" and "Subset (Killer)"? The rest like "Killer Naked/Hidden Subset", "Naked/Hidden Killer Subset" and "Killer Subset" can be created as redirect pages, if necessary. --unkx80 11:03, 19 February 2007 (CET)

On the whole I think "naked" isn't a good term (as explained in the foregoing posts) since they can be in fact quite hard to spot, unlike the naked pairs/triples/&c in regular sudoku. My suggestion is simply: rename the page to "Killer Subset" & have redirects for all the other variant names. There's no need to distinguish between the two techniques really as both are the same thing, approached by different logics. (To make this clear maybe the page could be rewritten to describe both logics for each example.)

I finally located that pesky JCGodart puzzle so I'll add the link now. --Nd 23:29, 19 February 2007 (CET)

Page Moved

This discussion has been taken place long enough without very active discussion, so I accepted Nd's proposal and simply moved it. However, the contents of this page now needs to be rewritten.

Nd et al., do you mind doing the rewriting? Thanks. --unkx80 08:07, 20 February 2007 (CET)

OK have done it; what it needs now is an illustration of the complementary logic for the 2nd, more complex puzzle. --Nd 15:33, 20 February 2007 (CET)