The New Sudoku Players' Forum

[Luke]

Everyone refers to difficulty ratings as "ER 8.5" or "SE 8.9" etc. What do these acronyms stand for?

I have "Sudoku Explainer" (SE?) but when I enter a puzzle I do not find a function that will display the puzzle's rating (as in, say, the "grader" in Sudoku Solver.)

"ER" remains a mystery. What's that story? And why are these ratings so universally accepted? (Pardon my backwardness....it took me months to figure out what "SSTS" meant!)

[udosuk]

I think "SE" and "ER" both refers to the "Sudoku Explainer Rating". Just a different preference for different solvers. I'm sure there is a selection from the menu to display the rating, but I don't use it so can't tell you how. (It seems each step has a rating itself and the rating for the whole puzzle is the hardest step necessary. )

See these links:
http://www.sudopedia.org/wiki/Sudoku_Explainer
http://diuf.unifr.ch/people/juillera/Sudoku/Sudoku.html

On the other hand, "SSTS" was coined by yours truly.

See these links:
http://www.sudopedia.org/wiki/SSTS
http://forum.enjoysudoku.com/viewtopic.php?p=34620#p34620

[Pat]

I have Sudoku Explainer
but when I enter a puzzle I do not find a function that will display the puzzle's rating

menu -- Tools -- Analyze

or just press F9

[Luke]

Thanks, Pat. That does the trick.

udosuk: So you're the culprit, eh? I appreciate the links/history lesson.

[Luke]

Haven't used the rating feature much, but something's awry in the way I'm using the program. Every puzzle I ask SE to analyze comes back with a difficulty rating of 7.2. I reloaded the program and got the same result. It's as if this version (1.2.1) maxes out at 7.2. Easier puzzles seem to yield various ratings. Here's three somewhat difficult puzzles. I'm wondering what ratings others get when they ask SE to analyze them:

Code: Select all

007260001300007600000900003409500000010000030000008204200005000006100005100076800
000080000001706800060502030047000310100000006085000720030901040009803200000050000
071000430800400002400005090000001900040902060003700000060500008200003009084000510

As far as the analysis itself is concerned, the solver seems to rely on what it calls "Forcing Chains." Maybe a forcing chain expert (Dan?) could verify that these are not forcing chains but discontinuous nice loops. In fact, it appears that every "forcing chain" the solver reveals is a weak discontinuous nice loop. By "weak" I mean it starts on a weak link rather than a strong, like this example:

Code: Select all

If we assume that R1C9 contains the value 9, it follows, through a Forcing Chain, that R1C9 cannot contain the value 9. Therefore we can conclude that R1C9 does not contain the value 9.

Most human solvers (around here, anyway) seem to rely more heavily on chains that start with a strong link. I've never seen SE come up with a chain that begins, "If we assume that R1C9 does not contain the value 9, it follows..."

[ronk]

I'm wondering what ratings others get when they ask SE to analyze them:

Code: Select all

007260001300007600000900003409500000010000030000008204200005000006100005100076800
000080000001706800060502030047000310100000006085000720030901040009803200000050000
071000430800400002400005090000001900040902060003700000060500008200003009084000510

All do have a 7.2 rating. Try this ...

Code: Select all

..1..2..3....4....2..5..4....6..1..7.3.....2.7..3..5....8..6..1....9....5..4..8..  #SE=8.3

I've never seen SE come up with a chain that begins, "If we assume that R1C9 does not contain the value 9, it follows..."

Neither have I.