C++ Reference: class DualBoundStrengthening

This documentation is automatically generated.

This detects variables that can move freely in one direction, or that can move freely as long as their value do not cross a bound.

TODO(user): This is actually an important step to do before scaling as it can usually reduce really large bounds!
Method
CanFreelyDecreaseUntil

Return type: int64_t

Arguments: int ref

The given ref can always freely decrease until the returned value. Note that this does not take into account the domain of the variable.

CannotDecrease

Return type: void

Arguments: absl::Span<const int> refs, int ct_index = -1

All constraints should be mapped to one of more call to these functions.

CannotIncrease

Return type: void

Arguments: absl::Span<const int> refs, int ct_index = -1

CannotMove

Return type: void

Arguments: absl::Span<const int> refs

ProcessLinearConstraint

Return type: void

Arguments: bool is_objective, const PresolveContext& context, const LinearProto& linear, int64_t min_activity, int64_t max_activity

Reset

Return type: void

Arguments: int num_variables

Reset the class to a clean state. This must be called before processing the constraints.

Strengthen

Return type: bool

Arguments: PresolveContext* context

Once ALL constraints have been processed, call this to fix variables or reduce their domain if possible. Note that this also tighten some constraint that are the only one blocking in one direction. Currently we only do that for implication, so that if we have two Booleans such that a + b <= 1 we transform that to = 1 and we remove one variable since we have now an equivalence relation.