cp_model_objective.h

// Copyright 2010-2018 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef OR_TOOLS_SAT_CP_MODEL_OBJECTIVE_H_
#define OR_TOOLS_SAT_CP_MODEL_OBJECTIVE_H_

#include "ortools/sat/cp_model.pb.h"

namespace operations_research {
namespace sat {

// If the objective contains more than one term, a new integer variable will be
// created and an equality constraint will be added to the model to force
// this new variable to be equal to the old linear combinaison defining the
// objective.
//
// If the objective contains only one term, we canonicalize it so that its
// coefficient is one. If there is no objecitve, this has no effect.
//
// The main raison to do that is that the objective can be preprocessed like
// any linear constraint before beeing "extracted" again.
//
// TODO(user): Add only a >= constraint? Not sure it is useful to do that before
// presolve, we can always do this optimization just before solving the model.
void EncodeObjectiveAsSingleVariable(CpModelProto* cp_model);

}  // namespace sat
}  // namespace operations_research

#endif  // OR_TOOLS_SAT_CP_MODEL_OBJECTIVE_H_