93 lines
2.9 KiB
C++
93 lines
2.9 KiB
C++
// Copyright 2010-2021 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Simple linear programming example
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#include <iostream>
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#include <limits>
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#include <string>
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#include <vector>
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#include "absl/status/statusor.h"
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#include "absl/strings/str_cat.h"
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#include "absl/strings/str_join.h"
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#include "absl/time/time.h"
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#include "ortools/base/init_google.h"
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#include "ortools/base/logging.h"
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#include "ortools/base/status_builder.h"
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#include "ortools/base/status_macros.h"
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#include "ortools/math_opt/cpp/math_opt.h"
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namespace {
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namespace math_opt = ::operations_research::math_opt;
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constexpr double kInf = std::numeric_limits<double>::infinity();
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// Model and solve the problem:
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// max 10 * x0 + 6 * x1 + 4 * x2
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// s.t. 10 * x0 + 4 * x1 + 5 * x2 <= 600
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// 2 * x0 + 2 * x1 + 6 * x2 <= 300
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// x0 + x1 + x2 <= 100
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// x0 in [0, infinity)
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// x1 in [0, infinity)
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// x2 in [0, infinity)
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//
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absl::Status Main() {
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math_opt::Model model("Linear programming example");
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// Variables
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std::vector<math_opt::Variable> x;
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for (int j = 0; j < 3; j++) {
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x.push_back(model.AddContinuousVariable(0.0, kInf, absl::StrCat("x", j)));
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}
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// Constraints
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std::vector<math_opt::LinearConstraint> constraints;
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constraints.push_back(
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model.AddLinearConstraint(10 * x[0] + 4 * x[1] + 5 * x[2] <= 600, "c1"));
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constraints.push_back(
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model.AddLinearConstraint(2 * x[0] + 2 * x[1] + 6 * x[2] <= 300, "c2"));
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// sum(x[i]) <= 100
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constraints.push_back(model.AddLinearConstraint(Sum(x) <= 100, "c3"));
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// Objective
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model.Maximize(10 * x[0] + 6 * x[1] + 4 * x[2]);
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ASSIGN_OR_RETURN(const math_opt::SolveResult result,
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Solve(model, math_opt::SolverType::kGlop));
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if (result.termination.reason != math_opt::TerminationReason::kOptimal) {
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return util::InternalErrorBuilder()
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<< "model failed to solve to optimality" << result.termination;
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}
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std::cout << "Problem solved in " << result.solve_time() << std::endl;
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std::cout << "Objective value: " << result.objective_value() << std::endl;
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std::cout << "Variable values: ["
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<< absl::StrJoin(result.variable_values().Values(x), ", ") << "]"
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<< std::endl;
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return absl::OkStatus();
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}
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} // namespace
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int main(int argc, char** argv) {
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InitGoogle(argv[0], &argc, &argv, true);
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const absl::Status status = Main();
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if (!status.ok()) {
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LOG(QFATAL) << status;
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}
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return 0;
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}
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