Sorry, I'm coming late in this thread.
Phil wrote:Are SDC and double ALS measuring the same thing?
For Phil's fifth and Leren's first (counter)-example, it has been proved
yes.
Note for Leren's puzzle, that yzfwsf has found a SDC matching Leren's ALS-XZ Rule Loop, but the reverse was also possible (find an ALS-XZ Rule Loop matching Leren's SDC):
- Code: Select all
*-----------------------------------------------------*
| 3 2 9 |P168 P1478 P1678 | 5 14 14678 |
| 458 48 17 |B1368 35-1478 P1678 | 168 2 9 |
| 458 6 17 |B189 259-1478 29-178 | 18 3 1478 |
|-----------+------------------------+----------------|
| 9 3 4 | 2 18 18 | 7 6 5 |
| 7 1 6 |P39 39 5 | 4 8 2 |
| 2 5 8 | 7 6 4 | 19 19 3 |
|-----------+------------------------+----------------|
| 468 7 3 | 168-9 1289 12689 | 1289 5 148 |
| 1 9 5 | 4 28 3 | 268 7 68 |
| 468 48 2 | 5 1789 16789 | 3 149 148 |
*-----------------------------------------------------*
Sue de Coq: Base Cells r23c4 {13689} Pincer Cells r5c4 {39} + r1c456, r2c6 {14678}
With the same cells: ALS XZ Rule Loop : ALS 1 r5c4; ALS 2 r1c456, r2c46, r3c4; Z = 3 & 9 => same eliminations as SDC
As regards Leren's second counter-example:
Leren wrote:The main difference is that, with the SDC you can get - 47 r7c6. With double ALS I can't see how you can get it, even though there were a number of double ALS moves available.
Leren, you are comparing an ALS-XZ Rule Loop in a set of cells that is not the Sue de Coq's.
Not surprising you find a different list of eliminations.
I assume that there is a typo when you write:
Sue de Coq: Base Cells r23c6 {24678} Pincer Cells r45c6 {247} + r1c45 {168} => - 1 r2c5, - 6 r3c4, - 8 r3c5, -47 r7c6, - 7 r9c6; stte
Should read Sue de Coq: Base Cells r23c6 {
124678} Pincer Cells r45c6 {247} + r1c45 {168}
The SDC Base is an AAAALS: 6 digits, 2 cells -> freedom degree 4 !!!
So each Pincer ALS must be linked to the base by
six restricted commons, in total (which is the case: r45c6 is linked by RCs 247, ric45 by RCs 168)
Consider the same cells, broken down into A, B (PM below): A is an ALS, but B is an AALS. They are triply linked, so you can consider the rank-0 logic: A -(168)- B => - 1 r2c5, - 6 r3c4, - 8 r3c5, -47 r7c6, - 7 r9c6; stte
- Code: Select all
*---------------------------------------------------------*
| 3 1568 568 |A16 A18 9 | 7 4 2 |
| 2479 1279 247 | 5 347-1 B1247 | 6 8 39 |
| 246789 26789 24678 | 2347-6 347-8 B24678 | 39 1 5 |
|---------------------+----------------------+------------|
| 2478 23578 234578 | 2479 4579 B247 | 2389 6 1 |
| 1 2357 9 | 8 6 B247 | 23 57 34 |
| 24678 25678 245678 | 12479 14579 3 | 289 57 49 |
|---------------------+----------------------+------------|
| 789 789 1 | 479 2 8-47 | 5 3 6 |
| 268 4 2368 | 36 38 5 | 1 9 7 |
| 5 3679 367 | 13679 1379 16-7 | 4 2 8 |
*---------------------------------------------------------*
"ALS/AALS XZ Rule" Loop : ALS 1 r1c45; AALS 2 r2345c6; Z = 1 & 6 & 8 => - 8 r1c23, - 1 r2c5, - 6 r3c4, - 8 r3c5, - 8 r8c5, - 7 r9c6; stte
AIC for this loop: (1247=6|8)r2345c6 - (68=1)r1c45 loop =>same eliminations.
This example brings to light the needed adjustments when transposing an extended SDC to an equivalent ALS XZ rule (notably adjusting the number of links and the freedom degree of ALS's)
Phil wrote:Are SDC and double ALS measuring the same thing? I had in mind the following:
(2=3)r2c1 - (3=2)r2c79, r13c8 - loop => same eliminations as Leren's SDC.
Are they ever non-equivalent? (I removed SDC from my solver because I thought they were)
eleven wrote:I thought so either, but don't know, if it is proved. What i like is, that there are rather different ways to spot it, as shown here.
Note that in Phil's fifth puzzle, as well as in Leren first counter-example, the ALS-XZ doubly linked were equivalent because it was possible to merge the SDC base with the ALS initially triply linked, to form the new "big ALS"
marek stefanik wrote:Obviously, there are cases of doubly-linked ALSs that SDC doesn't cover, since it's limited to one line and one box and therefore cannot detect for example doubly-linked ALSs in two rows.
Clearly, the answer to Phil's question depends upon the definition given to the SDC pattern.
When the pattern was invented by Sue de Coq, it was limited to
one line and one box, as stated by Marek. When I learned the pattern (in a document in French, around 2008) this limitation was not mentionned. Therefore, to me, the case considered by Marek, of "doubly-linked ALSs in two rows", was a Sue de Coq. It was clearly stated
here. Now, see the puzzle in
this thread: I have been tarred and feathered for that
.
However the extension makes sense; the limitation to one box and one line brings nothing from the logical point of view, only the links between subsets do. See also a more recent puzzle
here.
So, extending SDC base up to an AAAALS seems accepted without any doubt, but extending SDC location to a pair of sectors other than (box, line) or to a triplet of sectors seems still too much transgressive.
Frankly speaking, I'm lost.
But no matter, this is just a naming question. It doesn't change anything in the logic of the patterns.
Are SDC and double ALS measuring the same thing?
To me the answer to Phil's question is YES, in all cases, provided
consistent extended definitions of each term (SDC and double ALS) are accepted.
Nothing else than MHO.