Welcome to Systematic Sudoku. The blog is about “human engineered Sudoku solving”. This means practical and efficient ways for humans to solve Sudoku puzzles. And I mean humans, not computers. It’s about taking advantage of human abilities to discover the completed grid that is dictated by a set of given clues, without resorting to thousands to millions of organized stabs in the dark, which is the way computers are coded to do it, in many different ways.
Originally written on a weekly posting schedule, the posts have been left in the dated order, but revised to incorporate what I have learned as I have explored the principles that inspired me to start blogging. Just so you know, the update you are reading was done in September 2016.
I’m happy to report that, in all this time, my original concepts about human solving have held their ground. I have been able to demonstrate, not only that native human intelligence and vision can conquer Sudoku puzzles of all levels, but exactly how these ordinary abilities can accomplish that, when properly supported by – guess what – computers.
The “post and revise” nature of this blog means there is more than one best way to absorb it. Reading straight through by date, you get the narrative as I was originally able to conceive of what I was doing. As you go along, you hit many detours, to be taken if you are going to follow something called the Sysudoku Order of Battle. That is the recommended “when to do what”, designed to fit a puzzle of any level. The flowchart road map of the SOB is linked on the main menu above. Follow the posted detours if you are more interested in becoming an expert solver yourself.
If you came here from one of my much later posts with your head swimming, you can relax. You don’t need to get into all that to add a healthy dose of Sudoku to your life. Say you’d just like to do those daily newspaper puzzles or the armchair friendly puzzle books Dagwood’s wife Blonde likes. No problem. By the time you get through 2011 and try out Sysudoku basic solving on the original copies of your puzzles, you are there!
If you are an expert solver already, then just take in my second post, revised to announce innovations introduced or productively discussed throughout this blog. Then browse, making use of the Find It page linked above. Except for one thing. I’m not listening to anything you have to say, unless you have read through the basic solving posts of 2011 that follow, and understand slink marking, and the advanced solving topics of the next post.
I have to be clear also on what I mean by “Sudoku solving”. To me, making an arbitrary guess here and there, and stumbling on a solution is not solving. At the end, this effort has revealed nothing about the puzzle. The “solver” might as well have used the solution as a guide to the guesses. The solution itself is actually of no inherent interest. And nobody will care that you guessed the cell value, or that it was a cell value that collapsed the puzzle.
My continuing readers I salute with the label “sysudokies”. A sysudokie solves a puzzle by identifying a sequence of logical inferences that force the solution numbers into the cells of the puzzle. That sequence is an answer to the questions of “What is in this puzzle?” or “How tough is this puzzle?”
In this definition I’ve been careful to say “a sequence”, not “the sequence”. The solution can often be forced in more than one way. And besides that, the techniques for human solving are definitely not completely known, even in 2016.
But that’s not all. In order to communicate evaluations of puzzles and human solving accomplishment, the solving methods need to be applied in a reasonable order shared by the communicators. And in each stage, the process should be reasonably exhaustive. That is to say, when a puzzle falls by a particular method, it’s expected that it would not have been solved by an, easier and more efficient method of an earlier stage, because that should have been discovered. But we are human, and it happens.
In all this, I’m talking about direct human solving, as opposed to developing computer codes that find the solutions of Sudoku puzzles. That is just as legitimate as a human accomplishment. It’s just not of interest in this blog, outside of a computer algorithm being adapted to human solving. I’m even opposed to using computer codes for finding all candidates, or other solving tasks thought to be less than creative, or too much effort.
In my reviews, the “experts” I really go after in this blog are the computer coders who foist their organized stabbing algorithms on the unsuspecting public as human solving advice. They tend to forget that people are not computers.
Computers are very useful in Sudoku solving, however. My laptop and its standard office software archives puzzle collections and solving stages, and makes the visual displays that enlist the amazing visual abilities of the mind. WordPress, a nonprofit organization supporting bloggers worldwide, built the engine of this blog. I’m very grateful to this organization, and to Microsoft Office, excepting the dodo that ordered the replacement of the Brush Script font, with one of a different size.
Also, there is nothing here about composing puzzles. I use puzzles composed by expert composers. Computer codes play a large role in this, by following millions of pathways to determine if a partially composed puzzle still has a solution, and only one solution. That’s what computer do, but they don’t have any fun. Don’t be a computer.
So by “Systematic” I’m referring to a system used by a community of Sudoku solvers, the sysudokies. We shorten “Systematic Sudoku” to “Sysudoku”. Why a system? The fact is, to accomplish most with the abilities they have, humans have to be systematic, juggling the 6 or 7 thought items we can handle at once to cover tasks requiring much more. We’re not into searching through millions of possibilities. That is the primary ability of the computer. The essence of Sysudoku is replacing search by focused construction of simple logical entities that have small, manageable numbers of consequences. This blog explains how to recognize the opportunities for such constructions, exactly how to do them, and exactly why they work. Then it goes on to compare this system to every other approach I can find, and to measure how successful it is in available collections of puzzles.
If you aren’t yet a regular Sudoku solver, the Beginner’s Page is the place to go before the next post. The blog assumes nothing beyond that and builds from the very beginning into the current Sysudoku in which monster puzzles are solved, and the most difficult puzzle collections are reviewed. The solution process is documented by intermediate diagrams, and by text traces allowing the reader to follow each step if desired. This transparency remains unique in the Sudoku world, I kid you not.
Going from post to post, you will have the learning advantage of “homework”. You are often invited to do a next step, usually for the upcoming post, to be expected on Tuesday afternoon, 2 PM EST. A “checkpoint” in that post is provided for your detailed comparison.
With the detailed nature of the blog, and the conventions and jargon that comes with this detail, even experts may need to skim the posts and pages to get on board. The next post is primarily for them, going into what they can expect to find along the way. It’s no secret, and much of the jargon is decoded on the page labeled “Sysudoku Speak”. But really, there’s no need to look up any part of it. Just come back to this second post for perspective whenever you like.
Comments are welcome on the blog. I have to filter out scads of spam; that comes with the territory. So if you’d like for your comment to be published, don’t make it look like spam. Something else to know about comments is this. For readers, the comment remains with the post where you entered the comment. There’s an entry box on every post. So pick the right post to enter the comment.
Also, no matter how pleased I am with your comment, if it does not bring up something of interest to my readers, I don’t publish it. Corrective comments are especially welcome. I make mistakes, no big deal. I fix the post, and acknowledge the comment with a reply to your credit.
Negative comments are OK, but if you don’t like something, you must state why. Readers can learn something from that, and I will reply if I can contribute. However, your personal preferences and way of doing things belong in your blog, not mine.
Welcome to my blog.