I searched and found no fully symmetrical 17 clues problem.

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I searched and found no fully symmetrical 17 clues problem.

Postby jmehat » Wed Apr 26, 2006 1:59 pm

I searched all the fully symmetric dispositions of 17 givens on a 9x9 grid, with a program I wrote, and found no valid problem : every disposition of values had more than one solution. The search used the spare cycles of half a dozen of PCs for around three month.

It is not really a proof, as the validity of my search program is unproven. I, at least, am convinced this (negative) result is exact.

My 2 c.
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Postby tarek » Wed Apr 26, 2006 2:11 pm

I suppose you searched through 19s & 18s prior to your 3 month search started.......

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Re: I searched and found no fully symmetrical 17 clues probl

Postby gfroyle » Thu Apr 27, 2006 3:24 am

jmehat wrote:I searched all the fully symmetric dispositions of 17 givens on a 9x9 grid, with a program I wrote, and found no valid problem : every disposition of values had more than one solution. The search used the spare cycles of half a dozen of PCs for around three month.

It is not really a proof, as the validity of my search program is unproven. I, at least, am convinced this (negative) result is exact.

My 2 c.


Well done.... I am sure that you are correct...

Now for the puzzles with symmetry groups of order 4!

gordon
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Re: I searched and found no fully symmetrical 17 clues probl

Postby claudiarabia » Sun May 14, 2006 10:22 am

....all the fully symmetric dispositions of 17 givens on a 9x9 grid,....had more than one solution. .....[/quote]

As far as I know, none of the 17ers are symmetric. The 18ers are at least rotational symmetric and only with the 19ers the full mirror-symmetry begins. So you did everything correct.

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Postby ab » Sun May 14, 2006 1:14 pm

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Postby claudiarabia » Sat Jul 01, 2006 11:29 pm

ab wrote:there are 17s with diagonal symmetry:
http://forum.enjoysudoku.com/viewtopic.php?t=3570&highlight=symmetric


thank you, ab
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