Jerry's Blog  1.4.210
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Version 3
Sudoku Analyzer v. 3.0 released
Wed October 7 2020  2:29pmSudoku

When you press the buttons 'Analyze', 'Hint', 'Peek', or 'Solve', the Sudoku Analyzer sends a small Ajax packet to the server. The 'X' in A.J.A.X. in this case stands for 'executable', a program that runs on the hosting server at cyberjerry.info as a native BSD excutable or binary. The binary performs the requested task and sends another small packet back to your computer to complete the Ajax transaction. This program is written in C and assembly, compiled on the server using gcc, for maximum execution speed. (Sudoku analysis would run way too slowly in a scripting language.) The original and core part of the program, written in assembly, solves the Sudoku by means of simple and fast bitwise AND, OR, and XOR instructions in tightly coded repetitive loops. Its task is to solve the Sudoku grid, or exhaust all possibilities in trying to solve it. Upon finding one solution, it continues to repetitively loop, looking for additional solutions. It can thus report back to the C program whether the particular grid has one solution, multiple solutions, or no solution. Its secondary task is to construct the array used to make the Elimination Grid.

This simple but efficient assembly solver routine could (almost always) perform its task very quickly. Given an empty or nearly empty grid, even the fastest binary program would take too much time to try all possibilities, but it could continue to generate multiple solutions (as many as a million or more per second) until the calling C program said, "Enough!". When given a grid with several cells filled in and therefore fewer cells to solve, it could exhaust all possibilities in exponentially less time. Where it would take several days to find all the solutions for an empty grid, it could do the same in a couple seconds - less than one second on a fast web server - for a grid that had 60 or fewer empty cells. It could then report definitively to the C program that the grid had exactly one solution, multiple solutions, or no solution. The C program could then use this information to begin to analyze the grid and, in the case of a single solution Sudoku, could help the human operator with step by step hints. Thus was born the Sudoku Analyzer.

The middle range was a bit problematic, where the grid had between 8 and 20 cells filled in. Depending upon how the 8 to 20 cells were configured, they might in some cases prevent the assembly routine from generating solutions quickly. At the same time, so many unsolved cells meant that the assembly routine would repetitively loop exponentially more times trying to exhaust all possibilities, and the server would likely kill the program for taking too much processor time. None of the problematic grids tested were valid single-solution Sudokus; they either had no solution or multiple solutions. Or so I thought. So, a few years ago, to avoid the server timeout error, I added a loop counter, telling the assembly routine to quit if it had found no solution after 120 million loops, at which point the C program would report that the grid had "no solution, or too many to analyze."

This assembly solver routine has been the focus of my attention for the past several weeks. Written about 15 years ago, it was the first part of what eventually became the online Sudoku Analyzer. In the interim years I continued to make improvements and fix bugs in the interactive web page, and the server-side C program's analysis and hint logic, but the assembly routine remained mostly unchanged. Then, as noted in the previous blog article, Señor Manuel Navarro De La Hoz of Colombia sent me something I had never found: a single-solution Sudoku with only 17 cells filled in. For the reasons mentioned above, my assembly routine could not solve it nor exhaust all possibilities within the loop limit constraints. And I knew what I had to do: I had to go back to the beginning, and make the assembly language solver routine run smarter and faster.

The new assembly routine is more complex and more analytical than the old one. Rather than trying to solve every grid the same simple way, it examines the grid and ranks its unsolved cells and groups of cells according their possible valid contents. Similarly, rather than always trying the digits 1 through 9 in numerical order, it ranks the digits in an order more likely to produce valid results quickly. Finally, upon testing my new logic, it became apparent that extending the loop limit beyond a few million loops had very little impact. So my new routine tries to complete its work in under 8 million loops. If it fails, it might try a different order of digits and cells, then another, then another. 99.77% of the time it now does all its work with less than 20,000 loops, and should never make more than 20 million loops, even in worst cases, so the server should never complain that it is consuming too much processor time.

Since the above involves radical changes to the core assembly routine, this marks a major new release number for the Sudoku Analyzer, version 3.0.000. At this same version level, there are a few minor changes to the C portion of the server-side binary and to the client-side interface. One new feature you may notice is that, above the Elimination Grid, you may now click 'Stats' to see how many loops and how much time the binary is taking each time it is called. The overall Ajax time is there for reference; the new changes affect only the speed and efficiency of the server-side binary. I have no control over the Ajax process, which depends upon your connection speed and that of all the servers that pass the small Ajax packet back and forth between your computer and the server at cyberjerry.info.

Now, with all due respect to Señor Navarro, and with humble gratitude for his astute and successful answer to my Challenge, I am in no way relinquishing my Sudoku Analyzer's claim to be the best on the web. It was already the best, and now, thanks to Señor Navarro, it is even better. The website where he found the Sudoku that had my Analyzer (temporarily) stumped was nothing more than a collection of canned Sudoku grids and their final solutions. No step by step hints, no analysis, nothing.

As I compose this blog article, am also running a program on my home computer to generate Sudokus in various configurations of filled and empty cells, to continue testing my new logic. At this moment, this program has generated around 90 million grids, all of which the new logic is handling without failing, and without taking too much time. That's not to say that the Sudoku Analyzer is now without flaws, nor that 3.0.000 will be its final version. But if you find a problem, or if you ever come across another analyzer that performs like my Sudoku Analyzer, be sure to let me know.

 
Successful Challenger
The first successful Sudoku Challenge respondent
Sun August 23 2020  10:09amSudoku

A few days ago, an astute visitor* to the CyberJerry Sudoku page successfully responded to the Sudoku Challenge, the first CyberJerry visitor to do so. He found the Sudoku grid pictured which the Analyzer couldn't solve, and told me (in Spanish) how to solve it:

este sudoku lo saque de la pagina https://www.sudoku-online.org de categoria sudoku extremo #717, y su analizar dice que no tiene una solución, sin embargo por metodo analitico encuentro que F6 = 4 debido al 4 de E3 y el 4 de G5, tambien encuentro que I9 = 5 debido al 5 de D8 y al 5 de H4, al colocar estos dos números, ahora si dice que tiene solución única lo anterior esta pasando por que su analizador no está realizando el método más sencillo que es de eliminación directa o único número de la caja, mira la celda I1 = 8 se obtiene por ese método
translated to English:
this sudoku is taken from webpage https://www.sudoku-online.org category extreme sudoku #717, and your analyzer says it has no solution, however by an analytic method I find that F6 = 4 due to the 4 in E3 and the 4 in G5, also I find that I9 = 5 due to the 5 in D8 and the 5 in H4, upon placing these two numbers, now it says that it has one unique solution the above is happening because your analyzer isn't executing the simplest method which is direct elimination or the cell's only number, see how cell I1 = 8 is obtained by this method

*The Challenger is:

Manuel Navarro De La Hoz
birthplace: Galapa del departamento de Atlántico, país Colombia
his YouTube channel: Mr cocogames

I have reviewed the Sudoku in question and have confirmed that my Analyzer does indeed fail to solve it, and that Señor Navarro has described a correct method for solving it. As promised, I am hereby acknowledging the success and superior Sudoku skills of Sr Navarro, and am also working at correcting the problem in the Analyzer.

Congratulations and thanks to Sr Navarro!

  2 comments
rev. Sat Aug 29  8:31am
 
Ordinariate
How a pilgrim Church might emerge
Wed August 5 2020  5:09pmFaith/Philosophy

It would be unreasonable and unjust to expect priests and bishops in 2020 to forsake their lifestyle and social status and become poor homeless pilgrims. Likewise, the vast majority of Catholic homes of today are incapable of becoming true domestic churches, with the husband assuming the role of pastor and priest. This will take time, probably several generations. But there are a few who could begin, and here's one way it could possibly play out:

A single bishop somewhere might request permission to form an ordinariate (see box). Or a priest could request to do so, and then request ordination as bishop, so as to be able to ordain men to the priesthood. The by-laws of this ordinariate (read article)

 
Amateur Priests
Dream of a Church without property
Thu July 30 2020  7:53pmFaith/Philosophy

There are Christian communities that have no denominational name, no church buildings, none of the usual ecclesial trappings. Their weekly home meetings are punctuated at intervals by pastoral visits from an elder or 'bishop'. The elder has a clearly defined territory within which he moves in circuit-rider fashion, preaching, teaching, counseling, and accepting such food and lodging as are offered him. He has no home of his own, and so is unmarried. He is allowed to own only what clothes, books and personal items he can carry in a single large suitcase.

Why shouldn't the Catholic norm be similar? The local group is the family; the husband and father being also an ordained Catholic (read article)

  1 comment
 
Doctrines, Canons, Buildings
Radical thoughts about Church property
Thu July 23 2020  4:26pmFaith/Philosophy

Full-tilt panic over covid-19 has reached Nicaragua, following months of ministerial hand-wringing. To my knowledge, no outright church closings here, but that may be mostly because Ortega has not provided the desired cover of government mandates. Daily Masses discontinued at my parish. The main door barred and locked even during the single Sunday Mass; die-hard parishioners must enter and exit through the small side chapel and through quasi-barriers of shoe and hand disinfectants. Those who come forward for Communion must submit to a second alcohol hand cleansing, with Communion on the tongue disallowed. (Of course, some die-hards still bring their dogs to Mass, without face masks; am (read article)

  1 comment
 
4 Sudoku Challenges
Solve one of these four to win
Mon July 6 2020  12:39pmSudoku

Now that it's more and more difficult to find Sudoku grids that the CyberJerry Sudoku Analyzer (the 'Analyzer') can't analyze step by step, the great Sudoku Challenge is also becoming more difficult. To help out a bit, below are four Sudoku grids that the Analyzer can't analyze step by step. You just have to figure out how to solve one of these analytically (no guesswork) to qualify as a successful Sudoku Challenger. Click on any of the grids to bring it up in the Analyzer. Both it and you should be able to solve several cells. But at some point, the Analyzer gets stuck and can't give a hint. Can your brain keep analyzing beyond that point, and solve the puzzle? If so, click on the (read article)

  0 comments
rev. Fri Jul 17  7:49pm
 
Unavoidable Rectangle
When the Unique Rectangle technique is unavoidable
Fri June 19 2020  9:24pmSudoku

A recent round of minor enhancements and corrections has made the CyberJerry Sudoku Analyzer capable of analyzing increasingly tough Sudokus. Two results: the "New Puzzle" control now offers a "Genius" level, and the "Hint" feature may offer extremely complex hints, containing many interdependent sub-steps of a variety of advanced strategies. The added focus on complex Sudokus has had another unforeseen result: the possibility of encountering what I call the "Unavoidable Avoidable Rectangle". (Not being able to find any mention of the phenomenon in any other website, I claim the right to assign this name to it.) Let me explain: (read article)

  0 comments
rev. Thu Jun 25  7:40pm
The greatest destroyer of peace is abortion.
- Mother Teresa

Articles
All  
Faith/Philosophy
Sudoku
Computer
Misc.
10/7/20Version 3
8/23/20Successful Challenger 2
8/5/20Ordinariate
7/30/20Amateur Priests 1
7/23/20Doctrines, Canons, Buildings 1
7/6/204 Sudoku Challenges
6/19/20Unavoidable Rectangle
6/1/20Sudoku Challenge (2) 1
4/7/20Fear of Death 3
2/14/20Heads Up
1/11/20Billionth Birthsecond 1
12/31/19Versus-2 1
12/18/19Versus
12/3/19Copyright/left 2
10/24/19DePyper 1
7/19/19Schizophrenia 4
7/11/19New Math 1
6/2/19Times and Seasons 4
11/29/18Data Security 1
10/2/18Until 7
9/15/18Empty Chair 11
8/28/18Riddle me this 6
8/1/18Sudoku Challenge Answered 3
7/4/18Unrest in Nicaragua 7
5/9/18Some Specifics
4/20/18Crisis of Authority 4
3/17/18Theocracy 2
3/1/18Self abnegation 1
12/14/17Sudoku Challenge
12/2/17Blog End
11/16/17Meta Blog 6
Copyright (c) 2017-2020 Gerald DePyper - Jinotega, Nicaragua, C.A.
rev. 2020.09.23