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## Re: [Help-glpk] Help GLPK

**From**: |
Andrew Makhorin |

**Subject**: |
Re: [Help-glpk] Help GLPK |

**Date**: |
Wed, 19 Dec 2012 15:38:26 +0400 |

>* Does anybody have tried to solve a Sudoko instance with a BigM method*
>* (to say "all of the digits of a line must be different").*
Using integer variables (like 0 <= x[i,j] <= 9) to model sudoku
solutions together with "all different" constraints leads to a poor
formulation which is hard to solve with b&b. Much more efficient
formulation can be obtained by using binary variables x[i,j,k] that
model a mapping from the grid to {0,...,9}. See an example model
included in the glpk distribution (examples/sudoku.mod).
>* There is solution without this method.*
>* How can someone know where and when GLPK is "able" or not (actually*
>* the Simplex method used) to solve such problems. Any help on this*
>* would be appreciable.*
>* *