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# alldifferent_matrix(+Matrix)

Constrain the rows and columns of Matrix to be different values
*Matrix*
- A two dimensional square matrix of Variables or integer

## Description

This constraint is a matrix version of alldifferent. Matrix is a two
dimensional square (NxN) matrix, and the constraint ensures that the
elements in each row and column of the matrix are different. The same
value can occur in different rows and columns. It is logically
equivalent to imposing 2N alldifferent constraints, on each row and column,
but it allows more reasoning because it consider the rows and columns
together. This version uses alldifferent from lib(ic_global_gac), but the
extra inferences performed between the rows and columns themselves may be not
fully domain consistent. The maximum propagation occurs when the
variables' domains also have N values.

This is currently a prototype -- the constraint has not been tested
very extensively and little effort has been spent to optimise performance.
We welcome any feedback on using this constraint.

This constraint is described in J.-C. Regin and C. Gomes,
'The Cardinality Matrix Constraint', CP 2004.

## See Also

alldifferent / 1, fd_global : alldifferent_matrix / 1, ic_global : alldifferent_matrix / 1, fd_global_gac : alldifferent_matrix / 1