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#1: Twillis (twillis) on Feb 1, 2009 [HINT] [SPOILER]

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I agree, Twillis...my only niggling doubt is...I have a sneaking suspicion that what we call "edge logic" is actually "guessing", albeit very logical guessing...I'd call it "elimination guessing" for want of a better term. Does anyone at all see what I mean and why?...and why I consider it guessing as opposed to a puzzle "completely solvable without guessing"?

It takes a skilled(and patient)puzzlemaker indeed to compose a puzzle that one can solve without having to use a random "elimination" tactic(no matter how logically implemented)to make it solvable.

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I understand ozymoe's comments, and agree that it's more elimination guessing. Ah well either way it's a cute small puzzle that was a quick solve. Thank you!

Logical elimination.

Ditto #s 1, 5, 6. My question is.... why did the helper only get 1 single blue dot of the row of 4, yet not give the option of marking this as "requires guessing?" Not that I would have marked it that way, but still the option should be there.

There are two different programs that solve puzzles on this site. The one that runs when you push the "helper" button is a little Javascript program. I was looking back at it the other day and was really quite impressed with myself. It's only about 30 lines of code, smaller than the program that runs when you click "bigger" but it manages to solve many puzzles. However, it is really very stupid about multicolor puzzles, it can hardly do "color logic" at all, and when it gets stuck it just stops.

The one that runs when you submit a new puzzle is called the "checker" or "pbnsolve". This is a much, much bigger and more complex program that is written in C and runs on the webpbn server instead of your computer. It's a full blown AI thing. It's brilliant about color logic, probably better at it than most humans, and when it gets stuck it can make sensible guesses, explore them and back them out again if they don't work out. Pbnsolve can solve many puzzles that the helper can't, especially multicolor puzzles. Someday, when I have some time on my hands, I'll teach it edge logic too.

The pbnsolve program is the one that declares for nearly all puzzles if they have multiple solutions or not, and for many puzzles declares them to be logically solvable.

In this case, however, pbnsolve did not decide that the puzzle was logically solvable. I was the one who ruled that it was logically solvable.

Thanks for the explanation, Jan.

A suggestion to consider? Could the puzzles needing edge logic be marked in some unique way - so that we know to at least try that approach? Not with a question mark but some other symbol?

Thanks for the explanation about the two different solvers.

I'd thought of flagging puzzles that can be solved by line logic alone. I'd want to totally automate that though, making pbnsolve just a bit smarter so that it can reliably flag such cases. Maybe someday.

Some day is good enough for me - I appreciate all the effort you invested to make this website. My thanks.

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LOL Thanks!

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