C++ Reference: class PresolveContext

Note: This documentation is automatically generated.

Wrap the CpModelProto we are presolving with extra data structure like the in-memory domain of each variables and the constraint variable graph.

Method
AddImplication	Return type: void Arguments: int a, int b a => b.
AddImplyInDomain	Return type: void Arguments: int b, int x, const Domain& domain b => x in [lb, ub].
AddLiteralToObjective	Return type: void Arguments: int ref, int64_t value
AddToObjective	Return type: void Arguments: int var, int64_t value
AddToObjectiveOffset	Return type: void Arguments: int64_t delta
AffineRelationDebugString	Return type: std::string Arguments: int ref
CanBeUsedAsLiteral	Return type: bool Arguments: int ref
CanonicalizeAffineVariable	Return type: bool Arguments: int ref, int64_t coeff, int64_t mod, int64_t rhs Given the relation (X * coeff % mod = rhs % mod), this creates a new variable so that X = mod * Y + cte. This requires mod != 0 and coeff != 0. Note that the new variable will have a canonical domain (i.e. min == 0). We also do not create anything if this fixes the given variable or the relation simplifies. Returns false if the model is infeasible.
CanonicalizeDomainOfSizeTwo	Return type: void Arguments: int var If not already done, adds a Boolean to represent any integer variables that take only two values. Make sure all the relevant affine and encoding relations are updated. Note that this might create a new Boolean variable.
CanonicalizeObjective	Return type: ABSL_MUST_USE_RESULT bool Arguments: bool simplify_domain = true
CanonicalizeOneObjectiveVariable	Return type: ABSL_MUST_USE_RESULT bool Arguments: int var
CanonicalizeVariable	Return type: void Arguments: int ref A "canonical domain" always have a MinOf() equal to zero. If needed we introduce a new variable with such canonical domain and add the relation X = Y + offset. This is useful in some corner case to avoid overflow. TODO(user): When we can always get rid of affine relation, it might be good to do a final pass to canonicalize all domains in a model after presolve.
ClearPrecedenceCache	Return type: void Clear the precedence cache.
ClearStats	Return type: void Clears the "rules" statistics.
ConstraintIsInactive	Return type: bool Arguments: int ct_index Checks if a constraint contains an enforcement literal set to false, or if it has been cleared.
ConstraintIsOptional	Return type: bool Arguments: int ct_ref Checks if a constraint contains an enforcement literal not fixed, and no enforcement literals set to false.
ConstraintToVars	Return type: const std::vector<int>& Arguments: int c
ConstraintVariableGraphIsUpToDate	Return type: bool At the beginning of the presolve, we delay the costly creation of this "graph" until we at least ran some basic presolve. This is because during a LNS neighbhorhood, many constraints will be reduced significantly by this "simple" presolve.
ConstraintVariableUsageIsConsistent	Return type: bool Returns true if our current constraints <-> variables graph is ok. This is meant to be used in DEBUG mode only.
DomainContains	Return type: bool Arguments: int ref, int64_t value
DomainContains	Return type: bool Arguments: const LinearExpressionProto& expr, int64_t value This methods only works for affine expressions (checked).
DomainIsEmpty	Return type: bool Arguments: int ref Helpers to query the current domain of a variable.
DomainOf	Return type: Domain Arguments: int ref
DomainOfVarIsIncludedIn	Return type: bool Arguments: int var, const Domain& domain This function takes a positive variable reference.
DomainSuperSetOf	Return type: Domain Arguments: const LinearExpressionProto& expr Return a super-set of the domain of the linear expression.
EndMax	Return type: int64_t Arguments: int ct_ref
EndMin	Return type: int64_t Arguments: int ct_ref
ExploitExactlyOneInObjective	Return type: bool Arguments: absl::Span<const int> exactly_one Checks if the given exactly_one is included in the objective, and simplify the objective by adding a constant value to all the exactly one terms. Returns true if a simplification was done.
ExpressionIsAffineBoolean	Return type: bool Arguments: const LinearExpressionProto& expr Returns true iff the expr is of the form a * literal + b. The other function can be used to get the literal that achieve MaxOf().
ExpressionIsALiteral	Return type: bool Arguments: const LinearExpressionProto& expr, int* literal = nullptr Returns true iff the expr is a literal (x or not(x)).
ExpressionIsSingleVariable	Return type: bool Arguments: const LinearExpressionProto& expr Returns true iff the expr is of the form 1 * var + 0.
FixedValue	Return type: int64_t Arguments: int ref
FixedValue	Return type: int64_t Arguments: const LinearExpressionProto& expr
GetAbsRelation	Return type: bool Arguments: int target_ref, int* ref
GetAffineRelation	Return type: AffineRelation::Relation Arguments: int ref Returns the representative of ref under the affine relations.
GetFalseLiteral	Return type: int
GetLiteralRepresentative	Return type: int Arguments: int ref Returns the representative of a literal.
GetOrCreateAffineValueEncoding	Return type: int Arguments: const LinearExpressionProto& expr, int64_t value Gets the associated literal if it is already created. Otherwise create it, add the corresponding constraints and returns it. Important: This does not update the constraint<->variable graph, so ConstraintVariableGraphIsUpToDate() will be false until UpdateNewConstraintsVariableUsage() is called.
GetOrCreateReifiedPrecedenceLiteral	Return type: int Arguments: const LinearExpressionProto& time_i, const LinearExpressionProto& time_j, int active_i, int active_j The following helper adds the following constraint: result <=> (time_i <= time_j && active_i is true && active_j is true) and returns the (cached) literal result. Note that this cache should just be used temporarily and then cleared with ClearPrecedenceCache() because there is no mechanism to update the cached literals when literal equivalence are detected.
GetOrCreateVarValueEncoding	Return type: int Arguments: int ref, int64_t value Gets the associated literal if it is already created. Otherwise create it, add the corresponding constraints and returns it. Important: This does not update the constraint<->variable graph, so ConstraintVariableGraphIsUpToDate() will be false until UpdateNewConstraintsVariableUsage() is called.
GetReifiedPrecedenceKey	Arguments: const LinearExpressionProto& time_i, const LinearExpressionProto& time_j, int active_i, int active_j
GetTrueLiteral	Return type: int Some expansion code use constant literal to be simpler to write. This will create a NewBoolVar() the first time, but later call will just returns it.
GetVariableRepresentative	Return type: int Arguments: int ref Returns another reference with exactly the same value.
HasVarValueEncoding	Return type: bool Arguments: int ref, int64_t value, int* literal = nullptr Returns true if a literal attached to ref == var exists. It assigns the corresponding to `literal` if non null.
InitializeNewDomains	Return type: void Creates the internal structure for any new variables in working_model.
InsertVarValueEncoding	Return type: bool Arguments: int literal, int ref, int64_t value Inserts the given literal to encode ref == value. If an encoding already exists, it adds the two implications between the previous encoding and the new encoding. Important: This does not update the constraint<->variable graph, so ConstraintVariableGraphIsUpToDate() will be false until UpdateNewConstraintsVariableUsage() is called. Returns false if the model become UNSAT. TODO(user): This function is not always correct if !context->DomainOf(ref).contains(value), we could make it correct but it might be a bit expansive to do so. For now we just have a DCHECK().
IntersectDomainWith	Return type: ABSL_MUST_USE_RESULT bool Arguments: int ref, const Domain& domain, bool* domain_modified = nullptr Returns false if the new domain is empty. Sets 'domain_modified' (if provided) to true iff the domain is modified otherwise does not change it.
IntersectDomainWith	Return type: ABSL_MUST_USE_RESULT bool Arguments: const LinearExpressionProto& expr, const Domain& domain, bool* domain_modified = nullptr Same as IntersectDomainWith() but take a linear expression as input. If this expression if of size > 1, this does nothing for now, so it will only propagates for constant and affine expression.
IntervalDebugString	Return type: std::string Arguments: int ct_ref
IntervalIsConstant	Return type: bool Arguments: int ct_ref Helper to query the state of an interval.
IntervalUsage	Return type: int Arguments: int c
IsFixed	Return type: bool Arguments: int ref
IsFixed	Return type: bool Arguments: const LinearExpressionProto& expr
IsFullyEncoded	Return type: bool Arguments: int ref Returns true if we have literal <=> var = value for all values of var. TODO(user): If the domain was shrunk, we can have a false positive. Still it means that the number of values removed is greater than the number of values not encoded.
IsFullyEncoded	Return type: bool Arguments: const LinearExpressionProto& expr This methods only works for affine expressions (checked). It returns true iff the expression is constant or its one variable is full encoded.
LiteralForExpressionMax	Return type: int Arguments: const LinearExpressionProto& expr
LiteralIsFalse	Return type: bool Arguments: int lit
LiteralIsTrue	Return type: bool Arguments: int lit
logger	Return type: SolverLogger*
LogInfo	Return type: void Logs stats to the logger.
MarkVariableAsRemoved	Return type: void Arguments: int ref Functions to make sure that once we remove a variable, we no longer reuse it.
MaxOf	Return type: int64_t Arguments: int ref
MaxOf	Return type: int64_t Arguments: const LinearExpressionProto& expr
MinOf	Return type: int64_t Arguments: int ref
MinOf	Return type: int64_t Arguments: const LinearExpressionProto& expr Helpers to query the current domain of a linear expression. This doesn't check for integer overflow, but our linear expression should be such that this cannot happen (tested at validation).
ModelIsExpanded	Return type: bool The "expansion" phase should be done once and allow to transform complex constraints into basic ones (see cp_model_expand.h). Some presolve rules need to know if the expansion was ran before beeing applied.
ModelIsUnsat	Return type: bool
NewBoolVar	Return type: int
NewIntVar	Return type: int Arguments: const Domain& domain Helpers to adds new variables to the presolved model. TODO(user): We should control more how this is called so we can update a solution hint accordingly.
NotifyThatModelIsExpanded	Return type: void
NotifyThatModelIsUnsat	Return type: ABSL_MUST_USE_RESULT bool Arguments: const std::string& message = "" This function always return false. It is just a way to make a little bit more sure that we abort right away when infeasibility is detected.
NumAffineRelations	Return type: int Used for statistics.
ObjectiveCoeff	Return type: int64_t Arguments: int var
ObjectiveDomain	Return type: const Domain& Objective getters.
ObjectiveDomainIsConstraining	Return type: bool
ObjectiveMap	Return type: const absl::flat_hash_map<int, int64_t>&
params	Return type: const SatParameters&
PresolveContext	Arguments: Model* model, CpModelProto* cp_model, CpModelProto* mapping
PropagateAffineRelation	Return type: bool Arguments: int ref Makes sure the domain of ref and of its representative are in sync. Returns false on unsat.
random	Return type: ModelRandomGenerator*
ReadObjectiveFromProto	Return type: void Objective handling functions. We load it at the beginning so that during presolve we can work on the more efficient hash_map representation. Note that ReadObjectiveFromProto() makes sure that var_to_constraints of all the variable that appear in the objective contains -1. This is later enforced by all the functions modifying the objective. Note(user): Because we process affine relation only on CanonicalizeObjective(), it is possible that when processing a canonicalized linear constraint, we don't detect that a variable in affine relation is in the objective. For now this is fine, because when this is the case, we also have an affine linear constraint, so we can't really do anything with that variable since it appear in at least two constraints.
RecomputeSingletonObjectiveDomain	Return type: bool When the objective is singleton, we can always restrict the domain of var so that the current objective domain is non-constraining. Returns false on UNSAT.
RefDebugString	Return type: std::string Arguments: int ref To facilitate debugging.
RegisterVariablesUsedInAssumptions	Return type: void Make sure we never delete an "assumption" literal by using a special constraint for that.
RemoveAllVariablesFromAffineRelationConstraint	Return type: void
RemoveVariableFromAffineRelation	Return type: void Arguments: int var Advanced usage. This should be called when a variable can be removed from the problem, so we don't count it as part of an affine relation anymore.
RemoveVariableFromObjective	Return type: void Arguments: int ref Allows to manipulate the objective coefficients.
ScaleFloatingPointObjective	Return type: ABSL_MUST_USE_RESULT bool
SetLiteralToFalse	Return type: ABSL_MUST_USE_RESULT bool Arguments: int lit Returns false if the 'lit' doesn't have the desired value in the domain.
SetLiteralToTrue	Return type: ABSL_MUST_USE_RESULT bool Arguments: int lit
ShiftCostInExactlyOne	Return type: void Arguments: absl::Span<const int> exactly_one, int64_t shift
SizeMax	Return type: int64_t Arguments: int ct_ref
SizeMin	Return type: int64_t Arguments: int ct_ref
StartMax	Return type: int64_t Arguments: int ct_ref
StartMin	Return type: int64_t Arguments: int ct_ref
StoreAbsRelation	Return type: bool Arguments: int target_ref, int ref Stores/Get the relation target_ref = abs(ref); The first function returns false if it already exist and the second false if it is not present.
StoreAffineRelation	Return type: bool Arguments: int ref_x, int ref_y, int64_t coeff, int64_t offset, bool debug_no_recursion = false Adds the relation (ref_x = coeff * ref_y + offset) to the repository. Returns false if we detect infeasability because of this. Once the relation is added, it doesn't need to be enforced by a constraint in the model proto, since we will propagate such relation directly and add them to the proto at the end of the presolve. Note that this should always add a relation, even though it might need to create a new representative for both ref_x and ref_y in some cases. Like if x = 3z and y = 5t are already added, if we add x = 2y, we have 3z = 10t and can only resolve this by creating a new variable r such that z = 10r and t = 3r. All involved variables will be marked to appear in the special kAffineRelationConstraint. This will allow to identify when a variable is no longer needed (only appear there and is not a representative).
StoreBooleanEqualityRelation	Return type: bool Arguments: int ref_a, int ref_b Adds the fact that ref_a == ref_b using StoreAffineRelation() above. Returns false if this makes the problem infeasible.
StoreLiteralImpliesVarEqValue	Return type: bool Arguments: int literal, int var, int64_t value Stores the fact that literal implies var == value. It returns true if that information is new.
StoreLiteralImpliesVarNEqValue	Return type: bool Arguments: int literal, int var, int64_t value Stores the fact that literal implies var != value. It returns true if that information is new.
SubstituteVariableInObjective	Return type: ABSL_MUST_USE_RESULT bool Arguments: int var_in_equality, int64_t coeff_in_equality, const ConstraintProto& equality, std::vector<int>* new_vars_in_objective = nullptr Given a variable defined by the given inequality that also appear in the objective, remove it from the objective by transferring its cost to other variables in the equality. If new_vars_in_objective is not nullptr, it will be filled with "new" variables that where not in the objective before and are after substitution. Returns false, if the substitution cannot be done. This is the case if the model become UNSAT or if doing it will result in an objective that do not satisfy our overflow preconditions. Note that this can only happen if the substitued variable is not implied free (i.e. if its domain is smaller than the implied domain from the equality).
time_limit	Return type: TimeLimit*
UpdateConstraintVariableUsage	Return type: void Arguments: int c Updates the constraints <-> variables graph. This needs to be called each time a constraint is modified.
UpdateNewConstraintsVariableUsage	Return type: void Calls UpdateConstraintVariableUsage() on all newly created constraints.
UpdateRuleStats	Return type: void Arguments: const std::string& name, int num_times = 1 Stores a description of a rule that was just applied to have a summary of what the presolve did at the end.
VariableIsNotUsedAnymore	Return type: bool Arguments: int ref Returns true if this ref no longer appears in the model.
VariableIsOnlyUsedInEncodingAndMaybeInObjective	Return type: bool Arguments: int ref Returns true if an integer variable is only appearing in the rhs of constraints of the form lit => var in domain. When this is the case, then we can usually remove this variable and replace these constraints with the proper constraints on the enforcement literals.
VariableIsUniqueAndRemovable	Return type: bool Arguments: int ref Returns true if this ref only appear in one constraint.
VariableWasRemoved	Return type: bool Arguments: int ref
VariableWithCostIsUnique	Return type: bool Arguments: int ref Same as VariableIsUniqueAndRemovable() except that in this case the variable also appear in the objective in addition to a single constraint.
VariableWithCostIsUniqueAndRemovable	Return type: bool Arguments: int ref
VarToConstraints	Return type: const absl::flat_hash_set<int>& Arguments: int var
WriteObjectiveToProto	Return type: void
WriteVariableDomainsToProto	Return type: void Some function need the domain to be up to date in the proto. This make sures our in-memory domain are writted back to the proto.