eleven wrote:Andrew Stuarts Nishio consists of 2 multidigit forcing chains showing a contradiction.
What they have in common is, that they start with a single digit, setting it one time true and one time false.
Actually, I think in Stuart's solver that's a Digit Forcing Chain. His Nishio only uses a true assumption but forms two branches with that.
In both cases i cannot see any reason, why they stop their chains somewhere in the grid (where their contradiction arises), instead of continuing, until they get a contradition in the starting cell.
Me neither. Well, I can really only agree about Stuart's case, because I don't know anything about the Explainer's implementation (but I trust you).
Once again let me say that AIC's ARE NO PATTERNS, but an ASSUMPTIVE TRIAL & ERROR technique.
That's quite assumptive itself
A pattern is something, which has a structure, you can optically recognize in a grid. Examples are the patterns, which show you the hidden singles, many fish and wings, unique rectangles, deadly patterns and so forth. But no one can identify any non trivial AIC optically without following the chain.
I don't claim that I do - yet - but I don't consider it impossible. If you have a system that visualizes most kinds of strong links clearly, and your brain is very used to interpreting those visuals, I bet you start seeing full or at least partial chains without having to follow every link one at a time. I know I'm improving in that all the time, and many chain patterns are starting to stand out from the grid. It's like learning to read. At first you can process only one letter at a time, then a syllable, then a word, then a sentence, then a paragraph, and I guess some can even process a whole page with one glance. At first it's a strictly linear process, but with enough experience it starts happening so quickly that it appears almost parallel (or maybe it is, who knows how the brain really work).
And to follow it, you have to make the assumption, that a digit is true or false, just as you do with the nishios above.
No. To see the chain doesn't require following it, because it's built from recognizable parts -- strong links at both ends which are connected by alternating links. It's like connecting components that have well-defined interfaces. If you have a correctly built chain, you don't have to follow it to know what an assumption at one end produces in the other. Of course, it would be quite risky not to test your chain with an assumption, but it's not strictly necessary when building it in your mind. It just requires a paradigm shift in thinking and looking at things. I'm not quite there yet but I don't think it's impossible.
(Talking about paradigm shifts --I think this is very similar to why long-time procedural programmers often have a hard time learning object-oriented programming. It also requires a different way of looking at things, and incidentally quite similar to this.)
To get the AIC "(6)r9c13 = (6-2)r7c2 = r9c3 - r9c9 = (2-6)r8c9 = (6)r8c45 => -6 r9c4" SpAce had to make the assumption, that 6r7c2 is true. So it is just nonsense to claim "That is an unassumptive pattern-based elimination".
No. See what David said about that. I never had to make any assumption about the eventual elimination. It's not part of the chain.
This is my last attempt to make that clear here. If people don't want to accept the truth, it makes no sense, trying to explain it. At the end you are just lying to yourselves.
I'm not a big fan of lying to myself, and I gratefully accept wake-up calls if someone catches me doing it. I'm not yet convinced that I need to wake up from this. I usually agree with you, but I think you may be looking at this from a bit narrow window.
