is there a name for this rule

dukuso · Posted: Mon Sep 19, 2005 4:05 pm Post subject: is there a name for this rule

I'm not so familiar with the sudoku "rules" for solving.

I'm wondering, is there a name for this sudoku-rule, which
is called "hyper arc consistency" in constraint programming :

for every row r and every column c and every symbol s,
check whether there are valid candidates s1,s2,..,s9 for
positions (r,1),..,(r,9) [the places in that row, including c]
such that s_c=s and all the s_i are different.
If not, that (sub-) puzzle has no solution.

Same for columns, blocks.

Ruud · Site Admin

In Sudoku, it is called the only rule. Laughing

Ocean · Posted: Mon Sep 19, 2005 6:34 pm Post subject:

I found the paper "Sudoku as a Constraint Problem", where 'hyper arc consistency' (alldifferent) is mentioned. Later (final?) version of the paper in Modelling and Reformulating Constraint Satisfaction Problems. (Proceedings from the Fourth International Workshop. Sitges (Barcelona), Spain, 1 October 2005).

(After reading the latest version, I see that dukosu's magictour data set, and gordon's minimal sudokus are included as test sets - .)

dukuso · Posted: Tue Sep 20, 2005 2:55 pm Post subject:

I'm not so familiar with the sudoku "rules" for solving.

I'm wondering, is there a name for this sudoku-rule, which
is called "hyper arc consistency" in constraint programming :

for each cell x and each candidate s for x
check whether there are valid candidates s1,s2,..,s9 for
the other cells x1,..,x9 in that row,column,block
(including x, assuming x=xi)
such that s_i=s and all the s_j are different.
If not, then you can remove s as a candidate for x

Same for columns, blocks.

is this included by some other rules ?
does it imply some other rules ?

edit: I had got it wrong the first time, so I had to edit it
and reposted, else noone would have noticed ...

dukuso · Posted: Tue Sep 20, 2005 7:07 pm Post subject: