- Origin
CHIP
- Constraint
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- Arguments
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- Restrictions
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- Purpose
Consider a digraph described by the
collection.
is the number of circuits for covering
in such a way that each vertex belongs to a single circuit.
In addition the following constraint must also hold: on each
set of consecutive distinct vertices of each final
circuit, the number of vertices for which the attribute colour
takes his value in the collection of values should
be located within the range .
- Example
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The constraint holds since
the vertices of the collection correspond to a set
of disjoint circuits and since, for each set of 3 (i.e.,Β )
consecutive vertices, colour 1 (i.e.,Β the value provided by the collection)
occurs at least once (i.e.,Β ) and at most twice (i.e.,Β ).
- Typical
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- Symmetries
Items of are permutable.
An occurrence of a value of that belongs to (resp. does not belong to ) can be replaced by any other value in (resp. not in ).
can be decreased to any value .
can be increased.
Items of are permutable.
- Usage
Assume that the vertices of are partitioned into
the following two categories:
Using the constraint we can
express a constraint like: after visiting three consecutive
clients we should visit a depot. This is typically not possible
with the constraint since we do not know in
advance the set of variables involved in the
constraint.
- Remark
This constraint is a special case of the parameter
of the constraint of
CHIPΒ [Bourreau99].
- See also
common keyword:
Β (graph partitioning constraint).
used in graph description:
.
- Keywords
characteristic of a constraint:
coloured.
combinatorial object:
sequence.
constraint type:
graph constraint,
graph partitioning constraint,
sliding sequence constraint.
final graph structure:
connected component,
one_succ.