An Update on the Slink Marking Bypass


This first post of 2015 updates sysudokies on the slink marking bypass, a preliminary stage of box marking introduced in late 2014. Experience now warrants that the bypass, as it will now be referred to, be accorded a permanent starting position in the Order of Battle. Earlier assessments of its worth, as opposed to going immediately into full slink marking, are revised. An outstanding example from this week’s Sunday 5-star by Dave Green shows off the bypass at its best.

I had decided give myself a break, and put Dave’s Sunday Sudoku on the template for a relaxing hour, before doing the last minute editing of this very post on the Gordon Guide review. I soon discovered I had stumbled on a much better start for the bang up 2015 blog year I have for you.

green bypassIn case you don’t get the paper with Dave’s Sunday 5-stars, and would like to take your own shot at it before reading further, here it is:

To review the brief history of the bypass, it started just last October as an adaptation of Peter Gordon’s basic solving process, to be used in timed Sudoku solving contests. Peter was using the double line exclusion (dublex) and cross hatching to find clues, then doing a full number scan for candidates. Sysudoku basic finds candidates much more efficiently, but I thought it even better, under a time control, to bypass writing in marks in the search for clues. In contests you thus avoid wasting time filling in candidates that never get used. Our Akron Tournament is all about doing basic solving fast.

The bypass makes one exception to “no pencil marks”. We mark naked pairs as Sysudoku slink marks. I suppose if I actually find other subsets in the process, I would mark them too. The point is, to put aside closed cells and concentrate on still open ones.

At the October bypass introduction, I already had the Fiendish review posts on Wayne Gould’s “no pencil marks” (NPM) in the can. I was rather hard on him for pretending that hard puzzles could be logically solved, not guessed through, without them. The bypass did very well on the Fiendish review puzzles, but I thought the puzzles were probably tailored to make NPM look good. Now I know better. Sorry, Wayne. Now the sysudokie way is to start without most pencil marks, and add them as required.

In the meantime, I’ve concluded that starting box marking with a separate slide for the bypass takes no more box marking time. If anything, I get more total clues, which must mean that I see more. And the kicker is, that I look forward to that opening bypass stage. At this stage, 2-stars, 5-stars and monsters are treated the same. I now plan to make revisions in my early posts, to steer beginners into the bypass as they get sufficient experience with regular box marking, and can follow a chain of unwritten slink marks.

So if you took advantage of my beginning offer, and have now bypassed your way into Dave Green’s Sunday 5-star, you either need a checkpoint, or you don’t. The following trace continues past all the uncertainties. If you didn’t try it, and you are absolutely new, then review the first Sysudoku posts of 2011 to get up to speed on regular box marking first, then looking at the trace page as necessary, follow the trace on this one. It will open your eyes.

green bypass trYes, a 5-star solved by the bypass, but that doesn’t mean it isn’t a 5-star. Your trace can be very different, yet lead to the solution easily. My traces have to follow the sysudokie 2-D tracing rules, so that readers who follow those rules get a matching checkpoint.

Next we return to the Gordon Guide review for a few more posts. I’ll be glad when it’s over, and I think you will be too.

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About Sudent

My real name is John Welch. I'm a happily married, retired professor (computer engineering), timeshare traveling, marathon running father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. The blog is about Sudoku solving. It covers how to start, basic solving to find candidates efficiently, and advanced solving methods in an efficient order of battle. It is about human solving methods, not computer solving.
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