variable_and_expressions.cc

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// Copyright 2010-2025 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.
 
#include "ortools/math_opt/cpp/variable_and_expressions.h"
 
#include <cmath>
#include <limits>
#include <ostream>
#include <utility>
#include <vector>
 
#include "absl/base/attributes.h"
#include "ortools/base/logging.h"
#include "ortools/base/map_util.h"
#include "ortools/base/strong_int.h"
#include "ortools/math_opt/cpp/formatters.h"
#ifdef MATH_OPT_USE_EXPRESSION_COUNTERS
#include "ortools/math_opt/storage/model_storage_item.h"
#endif  // MATH_OPT_USE_EXPRESSION_COUNTERS
#include "ortools/util/fp_roundtrip_conv.h"
 
namespace operations_research {
namespace math_opt {
 
constexpr double kInf = std::numeric_limits<double>::infinity();
 
#ifdef MATH_OPT_USE_EXPRESSION_COUNTERS
LinearExpression::LinearExpression() { ++num_calls_default_constructor_; }
 
LinearExpression::LinearExpression(const LinearExpression& other)
    : ModelStorageItemContainer(other.storage()),
      terms_(other.terms_),
      offset_(other.offset_) {
  ++num_calls_copy_constructor_;
}
 
ABSL_CONST_INIT thread_local int
    LinearExpression::num_calls_default_constructor_ = 0;
ABSL_CONST_INIT thread_local int LinearExpression::num_calls_copy_constructor_ =
    0;
ABSL_CONST_INIT thread_local int LinearExpression::num_calls_move_constructor_ =
    0;
ABSL_CONST_INIT thread_local int
    LinearExpression::num_calls_initializer_list_constructor_ = 0;
 
void LinearExpression::ResetCounters() {
  num_calls_default_constructor_ = 0;
  num_calls_copy_constructor_ = 0;
  num_calls_move_constructor_ = 0;
  num_calls_initializer_list_constructor_ = 0;
}
#endif  // MATH_OPT_USE_EXPRESSION_COUNTERS
 
double LinearExpression::Evaluate(
    const VariableMap<double>& variable_values) const {
  double result = offset_;
  for (const auto& variable : SortedKeys(terms_)) {
    const auto found = variable_values.find(variable);
    CHECK(found != variable_values.end())
        << internal::kObjectsFromOtherModelStorage;
    result += terms_.at(variable) * found->second;
  }
  return result;
}
 
double LinearExpression::EvaluateWithDefaultZero(
    const VariableMap<double>& variable_values) const {
  double result = offset_;
  for (const auto& variable : SortedKeys(terms_)) {
    result +=
        terms_.at(variable) * gtl::FindWithDefault(variable_values, variable);
  }
  return result;
}
 
std::ostream& operator<<(std::ostream& ostr,
                         const LinearExpression& expression) {
  // TODO(b/169415597): improve linear expression format:
  //  - make sure to quote the variable name so that we support:
  //    * variable names contains +, -, ...
  //    * variable names resembling anonymous variable names.
  const std::vector<Variable> sorted_variables = SortedKeys(expression.terms_);
  bool first = true;
  for (const auto v : sorted_variables) {
    const double coeff = expression.terms_.at(v);
    if (coeff != 0) {
      ostr << LeadingCoefficientFormatter(coeff, first) << v;
      first = false;
    }
  }
  ostr << ConstantFormatter(expression.offset(), first);
 
  return ostr;
}
 
std::ostream& operator<<(std::ostream& ostr,
                         const BoundedLinearExpression& bounded_expression) {
  const double lb = bounded_expression.lower_bound;
  const double ub = bounded_expression.upper_bound;
  if (lb == ub) {
    ostr << bounded_expression.expression << " = " << RoundTripDoubleFormat(lb);
  } else if (lb == -kInf) {
    ostr << bounded_expression.expression << " ≤ " << RoundTripDoubleFormat(ub);
  } else if (ub == kInf) {
    ostr << bounded_expression.expression << " ≥ " << RoundTripDoubleFormat(lb);
  } else {
    ostr << RoundTripDoubleFormat(lb) << " ≤ " << bounded_expression.expression
         << " ≤ " << RoundTripDoubleFormat(ub);
  }
  return ostr;
}
 
double QuadraticExpression::Evaluate(
    const VariableMap<double>& variable_values) const {
  double result = offset();
  for (const auto& variable : SortedKeys(linear_terms_)) {
    const auto found = variable_values.find(variable);
    CHECK(found != variable_values.end())
        << internal::kObjectsFromOtherModelStorage;
    result += linear_terms_.at(variable) * found->second;
  }
  for (const auto& variables : SortedKeys(quadratic_terms_)) {
    const auto found_first = variable_values.find(variables.first());
    CHECK(found_first != variable_values.end())
        << internal::kObjectsFromOtherModelStorage;
    const auto found_second = variable_values.find(variables.second());
    CHECK(found_second != variable_values.end())
        << internal::kObjectsFromOtherModelStorage;
    result += quadratic_terms_.at(variables) * found_first->second *
              found_second->second;
  }
  return result;
}
 
double QuadraticExpression::EvaluateWithDefaultZero(
    const VariableMap<double>& variable_values) const {
  double result = offset();
  for (const auto& variable : SortedKeys(linear_terms_)) {
    result += linear_terms_.at(variable) *
              gtl::FindWithDefault(variable_values, variable);
  }
  for (const auto& variables : SortedKeys(quadratic_terms_)) {
    result += quadratic_terms_.at(variables) *
              gtl::FindWithDefault(variable_values, variables.first()) *
              gtl::FindWithDefault(variable_values, variables.second());
  }
  return result;
}
 
std::ostream& operator<<(std::ostream& ostr, const QuadraticExpression& expr) {
  // TODO(b/169415597): improve quadratic expression formatting. See b/170991498
  // for desired improvements for LinearExpression streaming which are also
  // applicable here.
  bool first = true;
  for (const auto vs : SortedKeys(expr.quadratic_terms())) {
    const double coeff = expr.quadratic_terms().at(vs);
    if (coeff != 0) {
      ostr << LeadingCoefficientFormatter(coeff, first);
      first = false;
    }
    const Variable first_variable = vs.first();
    const Variable second_variable = vs.second();
    if (first_variable == second_variable) {
      ostr << first_variable << "²";
    } else {
      ostr << first_variable << "*" << second_variable;
    }
  }
  for (const auto v : SortedKeys(expr.linear_terms())) {
    const double coeff = expr.linear_terms().at(v);
    if (coeff != 0) {
      ostr << LeadingCoefficientFormatter(coeff, first) << v;
      first = false;
    }
  }
  ostr << ConstantFormatter(expr.offset(), first);
  return ostr;
}
 
std::ostream& operator<<(std::ostream& ostr,
                         const BoundedQuadraticExpression& bounded_expression) {
  const double lb = bounded_expression.lower_bound;
  const double ub = bounded_expression.upper_bound;
  if (lb == ub) {
    ostr << bounded_expression.expression << " = " << RoundTripDoubleFormat(lb);
  } else if (lb == -kInf) {
    ostr << bounded_expression.expression << " ≤ " << RoundTripDoubleFormat(ub);
  } else if (ub == kInf) {
    ostr << bounded_expression.expression << " ≥ " << RoundTripDoubleFormat(lb);
  } else {
    ostr << RoundTripDoubleFormat(lb) << " ≤ " << bounded_expression.expression
         << " ≤ " << RoundTripDoubleFormat(ub);
  }
  return ostr;
}
 
#ifdef MATH_OPT_USE_EXPRESSION_COUNTERS
QuadraticExpression::QuadraticExpression() { ++num_calls_default_constructor_; }
 
QuadraticExpression::QuadraticExpression(const QuadraticExpression& other)
    : ModelStorageItemContainer(other),
      quadratic_terms_(other.quadratic_terms_),
      linear_terms_(other.linear_terms_),
      offset_(other.offset_) {
  ++num_calls_copy_constructor_;
}
 
ABSL_CONST_INIT thread_local int
    QuadraticExpression::num_calls_default_constructor_ = 0;
ABSL_CONST_INIT thread_local int
    QuadraticExpression::num_calls_copy_constructor_ = 0;
ABSL_CONST_INIT thread_local int
    QuadraticExpression::num_calls_move_constructor_ = 0;
ABSL_CONST_INIT thread_local int
    QuadraticExpression::num_calls_initializer_list_constructor_ = 0;
ABSL_CONST_INIT thread_local int
    QuadraticExpression::num_calls_linear_expression_constructor_ = 0;
 
void QuadraticExpression::ResetCounters() {
  num_calls_default_constructor_ = 0;
  num_calls_copy_constructor_ = 0;
  num_calls_move_constructor_ = 0;
  num_calls_initializer_list_constructor_ = 0;
  num_calls_linear_expression_constructor_ = 0;
}
#endif  // MATH_OPT_USE_EXPRESSION_COUNTERS
 
}  // namespace math_opt
}  // namespace operations_research