The New Sudoku Players' Forum

[ttt]

ttt, for interest sake, Steve often wrote (pair38=2)r67c5, in this situation.

Thanks and yes, I thought about that but it's longer...

ttt

[Allan Barker]

Like Luke, I often just try to get a feel for the author's intent since I may not fully understand the notation anyway, particularly in cases like this since where there are no already revealed hidden or naked pairs.

However, even when the hidden/naked logic is cluttered (un-revealed), there might be a criteria for choosing either hp or np. A real naked pair has two bi-value strong links in its cells, while a real hidden pair has two strong bi-value (bi-local?) links along a row/column or a box. Thus, np might be a better term for logic that relies on the naked strong links and hp for logic relying on hidden strong links.

In his examples, ttt is using the 'naked' strong links.

Code: Select all

01: (hp38=2)r67c5-(2)r9c56=(2)r9c7-(2)r1c7=(2)r1c56-(2=8)r2c6 => r3c5<>8
02: (hp25=6)r13c5-(6)r2c4=(6-2)r2c8=(2)r7c8 => r7c5<>2, singles to the end 


.

[aran]

Revelation=>previously hidden.
In the first case what is revealed is a (previously) hidden naked pair.
In the second what is revealed is a (previously) hidden hidden pair.

Wow, we actually somewhat agree on something. What I don't agree with is subsequently dropping the primary adjective rather than the secondary adjective, and thereby changing "hidden naked pair" into "hidden pair".

"Hidden" does occupy 75% of the total adjectival space...
You wouldn't disagree with the term "hidden sets" as an general description ?
Just to anchor the hidden naked/hidden hidden distinction, there is a good example in Draco's recent sudoku

Code: Select all

*--------------------------------------------------------------------*
 | 28     236    268    | 2369   4      5      | 7      1      289    |
 | 2458   23456  1      | 2369   239    7      | 3469   3489   2489   |
 | 9      23467  2467   | 1      8      36     | 346    5      24     |
 |----------------------+----------------------+----------------------|
 | 6      1      478    | 5      379    3489   | 2      3489   489    |
 | 3      247    9      | 24     127    148    | 5      48     6      |
 | 248    24     5      | 23469  239    34689  | 349    7      1      |
 |----------------------+----------------------+----------------------|
 | 7      8      46     | 49     5      2      | 1      469    3      |
 | 124    2469   246    | 7      139    1349   | 8      2469   5      |
 | 1245   2459   3      | 8      6      149    | 49     249    7      |
 *--------------------------------------------------------------------*


13r8c56=1r9c6 : 2 candidates (13) 3 cells (r8c56+r9c6) : hidden hidden pair (ttt's move)
49(r7c4+r9c6)=1r9c6 : 3 candidates (149) 2 cells (r7c4+r9c6) : hidden naked pair

[Steve K]

My rapidly diminishing 2 cents worth:
A naked set is derived by looking at the contents of cells. It relies upon the sudoku truth: there must be at least one candidate in each cell.

A hidden set is derived by looking at the potential locations of candidates. It relies upon one of the following sudoku truths: there must be at least one location for a particular candidate in (row, column, box).

Some may be confused by the weak inferences also used in the derivations of each. However, it is the native strong inference sets that determine the "nakedness" or "hiddenness".

Thus, following the convention of which sis are being considered seems natural when using the terms, "hidden" and "naked" in chains.

[DonM]

My rapidly diminishing 2 cents worth:

Seems as if the recession is affecting everything!

(Nice to hear from you Steve).

[ronk]

On using Eureka!/AIC notation.
01: (hp38=2)r67c5-(2)r9c56=(2)r9c7-(2)r1c7=(2)r1c56-(2=8)r2c6 => r3c5<>8
02: (hp25=6)r13c5-(6)r2c4=(6-2)r2c8=(2)r7c8 => r7c5<>2

ttt, how are those hidden pairs?

I don’t know… , I follow the name that Steve used.

Take a look at your two usages of "hp" in the 2nd AIC here. It's a different usage, so which actually follows Steve Kurzhal's usage?

But first, please state your name for the jury. Now, please raise your hand and say after me 'The testimony I will give in these proceedings is the truth, the whole truth and nothing but the truth, so help me God.'

Now that ttt and Steve K have "testified" ... have you made a decision in this case

[DonM]

On using Eureka!/AIC notation.
01: (hp38=2)r67c5-(2)r9c56=(2)r9c7-(2)r1c7=(2)r1c56-(2=8)r2c6 => r3c5<>8
02: (hp25=6)r13c5-(6)r2c4=(6-2)r2c8=(2)r7c8 => r7c5<>2

ttt, how are those hidden pairs?

I don’t know… , I follow the name that Steve used.

Take a look at your two usages of "hp" in the 2nd AIC here. It's a different usage, so which actually follows Steve Kurzhal's usage?

But first, please state your name for the jury. Now, please raise your hand and say after me 'The testimony I will give in these proceedings is the truth, the whole truth and nothing but the truth, so help me God.'

Now that ttt and Steve K have "testified" ... have you made a decision in this case

(Intro all in the name of good humor & nothing more )

Largely asked and answered counsellor, but I'll make a summation:



Broad view already stated previously:

The way I see it, labels are more of a personal form of expression depending on one's concepts and thus, allow for more flexibility. Therefore, the 'why one uses a particular label' should be more in the line of interest value rather than judgment value. And that is why I don't think there is an absolute right or wrong here. I may prefer to use 'als' for patterns that others use 'hp' for. I might prefer to use 'hp' where some might use 'ahp'.

My specific preference at the moment (subject to change as my thoughts on the matter evolve just as my solving evolves):

It is based on my looking at sudoku solving as that of mainly recognizing patterns. The labels I use try to maintain a consistency based on the relationship of the strong/weak links in the pattern and the original description of the solving patterns they are derived from.

Take the description of the Almost Locked Set: Can be used as a strong inference between participating candidates. When all candidates of a single digit within the set are connected with a weak input link, the remaining candidates are locked in the set. The candidates for any of the remaining digits can therefore be used in a subsequent weak output link. Thus, if the pattern has an 'internal' strong link and the chain uses the 'external' output weak link, then I use the label 'als' regardless of whether a pair is involved. When describing an ALS Chain, no distinction is made when sets have pairs so neither do I.

Now take the description of Hidden Subset: Candidates are eliminated from the cells that hold the subset. This technique is very similar to naked subsets, but instead of affecting other cells with the same row, column or block, candidates are eliminated from the cells that hold the subset. Thus, I use the label 'hp' when the pattern makes use of 'internal weak link(s)' that exist between the hidden pair and the other candidates. Fwiw, I don't use 'ahp' because the hp label is placed after the incoming strong link although the overall technique being used is that of an 'almost hp'.

(The above assumes pairs for the sake of discussion at the moment.)

[ronk]

DonM, I'm sorry you felt the need to write a short story, as I sure didn't mean for you to spend that much time. And because of poor phrasing of my question, it really didn't get answered. So let me rephrase the question, so you can answer with a single sentence.

On using Eureka!/AIC notation.
01: (hp38=2)r67c5-(2)r9c56=(2)r9c7-(2)r1c7=(2)r1c56-(2=8)r2c6 => r3c5<>8
02: (hp25=6)r13c5-(6)r2c4=(6-2)r2c8=(2)r7c8 => r7c5<>2

I know you avoid the 'ahp' and 'anp' terms. I also know you prefer to use the 'als' term but, if you did not, would you use 'hp' or 'np' in the above?

[DonM]

DonM, I'm sorry you felt the need to write a short story, as I sure didn't mean for you to spend that much time.

More a precis than a short story, although summations are never short ;). Besides, much of it is for general consumption in case the subject arises again. However, henceforth answers here will be short.

And because of poor phrasing of my question, it really didn't get answered. So let me rephrase the question, so you can answer with a single sentence.

On using Eureka!/AIC notation.
01: (hp38=2)r67c5-(2)r9c56=(2)r9c7-(2)r1c7=(2)r1c56-(2=8)r2c6 => r3c5<>8
02: (hp25=6)r13c5-(6)r2c4=(6-2)r2c8=(2)r7c8 => r7c5<>2

I know you avoid the 'ahp' and 'anp' terms. I also know you prefer to use the 'als' term but, if you did not, would you use 'hp' or 'np' in the above?

np

[aran]

Don, Ronk
To that same question, I would have answered "no, neither".
I rarely use letters in my chains : : which I find unnecessary (eg 12=3 speaks for itself) and worse unpleasing to the eye.