Cull SCEs.

[Børge]

Very Moderate

500080007000009000098000000900030800000005600000006070005300720002000000000200000
020000003400002000010300004009000040100009708000027000070530090000700000056000000
000700900004000000063200085000008003008500600300070090450020806000005200800000000
700000000003005000050290031006300050800500900020000004407901500200000000000000000
000040080000000500586900100090005700007200006800000400030650000008002000000000000
420006000700000004000700800009002008300800005001005090034108720005000000000060000
000502000200000000900008070409020050000300008000900006008046000000000500047000000
000000000000000806000864000003000007000000501870140000000920005300001000057000920
020509300000000000700040005600900070805300006000006010306000000009100000000000000



Moderate

000004080400000300609080000000000000002000600043610050007002015000701000000000000
009000060000600000600020005006008009000000600005230007520003700001000003000000010
000800000506007000004006503000003000007000400240570600402009001000005900000000000
007093008005008100000000700000005040000001007209070010086400000000002800030000090
700000000000001000000508401000000030009807005100050090020700950600300007000000000
000001270000000000190040060009000003000006000601300800908600001000000000002009000
500100700200000000000007043001039000005000004000000600000372000306000000007000000
000005300007000000590300001200057004000000006070040800006402007003000000000100000
060000000007006005400530071000800007004000300570040010000407100001000000000000000



Moderate

000007050000400000173060200000102400000000500426070000004019300000008000300000080
380100000005000000000209006000001009000003000001800520010035060406000200000000800
003000000005000200700409010000900607000300000100007000308010470400000005000000000
000400000209006001000001008000100000005000007300240060030050020002800006008000900
005906000000000208100020090000050000004000002500304000800039005000000700000000010
000004800600500000000030001100000000000000400900046007000000005000000900519800000
050084600000500000900000008012000000400009800000700061020030907000000000001000040
009800607100003000000500040500002014700000000090300000060700200008000000000000008
000400501002000007070350000068074000001000000000000652300002706800700000007009000



Barely Extra Hard

000007050000400000173060200000102400000000500426070000004019300000008000300000080
380100000005000000000209306000001009000003000001800520010005060406000200000000800
003000000005000000700409010000900607000300000100007000308010470400000005000000000
000400000209006001000001008000000000005000007300240060030050020002800006008000900
005906000000000208100020090000050000004000002500304000800039005000000700000000010
000004800600500000000030001100000000000000400900046007000000005000000900519800000
050004600000500000900000008012000000400009800000700061020030907000000000001000040
009800607100003000000500040500002014700000000090300000060700200008000000000000008
000400001002000000070350000068000000001000000000000652300002706800700100007009000

[JLynn]

Good stuff! Worked through the Barely Extra Hard. Would've been easier had I realized initially that the Clueless puzzle was also Center-dot!

Which begs the question: Are the clueless puzzles in all your Explosions center-dot? To my recollection, all of Ruud's Explosions that I solved never were. If so, cool. If not, then I guess that's just something to keep us guessing.

[Børge]

jsmif and JLynn, thanks for your kind comments.

Which begs the question: Are the clueless puzzles in all your Explosions center-dot? To my recollection, all of Ruud's Explosions that I solved never were. If so, cool. If not, then I guess that's just something to keep us guessing.

I have not yet solved the Barely Extra Hard myself, so I cannot comment on this puzzle specifically. My generation method does not guarantee that a Clueless Explosion puzzle requires Center-Dot solving techniques. But if it does I personally think that this is a bonus. I can also not remember any of Ruud’s CEs actually being Center-Dot.

For SCE #6, the reason for the discrepancy between the rating based on the required solving techniques, and my personal rating based on actual solving, is that this puzzles either requires Center-Dot solving techniques or very advanced techniques like Almost Locked Sets or Medusa Colouring (I just undid my solving back to the point where Center-Dot is necessary to continue using basic techniques only, and checked with SudoCue).
This puzzle is 100% generated by JSudoku, so absolutely all credit for this puzzle (which I personally found very enjoyable) goes to Jean-Christophe. If all CEs generated by JSudoku actually require Center-Dot solving techniques, presumably only JC can answer. I hope he tunes in and lets us know.

Before posting SCE #6 I had not solved it myself. On Friday I decided to solve it during my lunch break, and assumed that it would be a relaxing walk in the park. After approx an hour of solving without nailing a single solution for the last half an hour, some perspiration was showing on my face. Then I remembered that each outer grid actually is a Center-Dot Sudoku, and then I was able to continue and solve it using the required solving techniques only. It’s a long time since I had such a long and enjoyable lunch break.

Good stuff! Worked through the Barely Extra Hard. Would've been easier had I realized initially that the Clueless puzzle was also Center-dot!

It’s soothing to know that I am not the only one that had forgotten that all the outer grids in a CE actually are Center-Dot.

Hope that others also have forgotten this and had as much struggle with SCE #6 as I had

[Jean-Christophe]

Which begs the question: Are the clueless puzzles in all your Explosions center-dot? To my recollection, all of Ruud's Explosions that I solved never were.

All 9 Sudokus in Clueless Explosions are center-dot by definition. As Ruud explains here (bold text second paragraph )

But AFAIK, the Clueless itself is not center dot, only the 9 regular Sudokus are.

[Børge]

JC, I think that there are some misunderstandings here, respectively some unfortunate phrasing.

No one disputes that all the 9 outer grids in a Clueless Explosion are Center-Dot and that the 10th Clueless grid is NOT Center-Dot. The point is: do you to solve a CE need to take into account that each outer grid is Center-Dot? As far as I can remember I did not have to take this into account for the Ruud CEs I have solved (I have not solved all 85). For all Ruud CEs I have solved, I solved all the outer grids as vanilla Sudokus using basic solving techniques only, and not using any of the special techniques applicable to a Center-Dot Sudoku (only). For instance: that in each outer grid all the 9 clueless cells must have a different value.

Below an example. Here I have highlighted (yellow) all the clueless cells having a pencil 8. Since each of the columns 2, 5, 7 and 8 in the clueless grid must have an 8 somewhere, all pencils 8 in the corresponding columns in the outer grids can be eliminated (the pink coloured cells). Without taking this into account this CE cannot be solved using basic techniques only.

My question to you was: Does JSudoku always generate CEs that require Center-Dot Sudoku techniques for solving?

[Børge]

After having examined the solution to the Barely Extra Hard puzzle, I realised that the 10th Clueless grid actually is Center-Dot, i.e. that the 9 cells

g10:r2c2   g10:r2c5   g10:r2c8
g10:r5c2   g10:r5c5   g10:r5c8
g10:r8c2   g10:r8c5   g10:r8c8

have different values.

This is absolute accidentally and not true for the first two cull SCEs. Since my generation method starts with the solution to the 10th Clueless grid I could actually decide to make the Clueless grid Center-Dot. Let’s see what I can think of for the next SCE.

JLynn,
I am sorry if I have misunderstood you, which I probably have.

[jsmif]

I was using center dot techniques for SCE#6 all along. Using Jsudoku as a solver (and seeing all grids simultaneously) makes this an intuitive technique, as once you have identified an intersection in the clueless grid (in the example above, '8' is locked in the middle column of the third nonet of the clueless), the obvious step is to eliminate '8' for the rest of the middle column in BOTH the clueless and outer grids.

[Jean-Christophe]

JC, I think that there are some misunderstandings here, respectively some unfortunate phrasing

Sorry, I misunderstood the question.

My question to you was: Does JSudoku always generate CEs that require Center-Dot Sudoku techniques for solving?

No, it does not.

Indeed the generator and recursive solver are unrelated to logical techniques. It's just using brute force and does not "know" what switching between subgrids and clueless means. It does not even "know" logical techniques like locked candidates, naked or hidden subsets... The recursive solver makes absolutly no difference between a naked pair, a hidden pair or an X-Wing which are all considered equally "hard" by the recursive solver, wherever they are: outer grid or clueless. These are all susbsets of size 2 which all count for one guess.

The only way to rate a puzzle is to solve it yourself. Examining JSudoku's log may help here. FYI, intersections (locked candidates) naked or hidden subsets and most techniques look first in "compact" houses before looking in "sparse" houses: nonets in outer grids first, then rows and columns in outer grids. Finally, if no useful pattern was found in the outer grids, it will test rows, columns and nonets in the clueless grid. So, if the log list some locked candidate or naked subset involving the clueless, it probably requires switching between outer grids and clueless.

Hope this clarify a bit...

[JLynn]

Indeed I guess I have to make myself more clear. I though when I had mentioned the "Clueless puzzle" I was referring to the 10th puzzle. No worries about misunderstanding.

[Børge]

I though when I had mentioned the "Clueless puzzle" I was referring to the 10th puzzle. No worries about misunderstanding.

Due to people having and using different terminologies, misunderstandings happen. As long as it eventually can be figured out it is not a real problem.

Under Clueless Puzzle I personally understand a complete clueless puzzle like a Clueless Explosion, Clueless Special or a similar complete Sudoku puzzle. Personally I use "The (10th) Clueless Grid" to reference the Clueless Grid alone, and "Outer Grid N" (1<= N <= 9) for referencing any of the other grids in a Clueless Explosion or Clueless Special. But that’s just my personal preference.

I find different terminologies a small annoyance when using different solvers.

[Børge]

Which begs the question: Is the clueless grid in all your Explosions center-dot? To my recollection, all of Ruud's Explosions that I solved never were.

As Ruud explains here, in his first 40? Clueless Explosion puzzles the 10th clueless grid was also center-dot.

My generation method does not guarantee that the 10th Clueless grid is Center-Dot.
Since my generation method starts with the solution to the 10th Clueless grid I could actually decide to make the Clueless grid Center-Dot.

So I could make a Clueless Special where the 10th clueless grid is center-dot:





A more extreme version would be a Clueless Explosion Special with 11 grids. The 10th and 11th clueless grids not necessarily being center-dot.

[JLynn]

Which might be cool for an occasional challenge, but there comes a point where it gets ridiculous. Ruud's MOAG and DOAG puzzles, for example. Or your proposed 8-ring monster. Not to say I wouldn't mind seeing it, but darned if I could actually solve such a thing.

[Sarah]

But perhaps once every month or 2 - looks like much fun. I'd definitely be interested in trying at least one. Thanks for all the efforts you are making.

[Pete]

I never knew the 10th puzzle was center dot

I guess I'll try a fey of the old ones and see.

Its kinda obvious that the component1-9 puzzles must be center dot and thats very usefull at times.

Thanks again for All the puzzles Borge,

It seems like even the easy versions are a bit harder than Ruud's

[Børge]

JLynn, Sarah and Pete, thanks for your feedback.

Pete,
Was Substitute Samurai #2 to your liking?

It seems like even the easy versions are a bit harder than Ruud's

I wonder if my Clueless Explosions are more Center-Dot demanding than Ruuds'? Anyone having an opinion on this?