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// Copyright Artelys for RTE.
// 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.
// This example that shows how to use Xpress Solver.
#include <cstdlib>
#include "ortools/base/commandlineflags.h"
#include "ortools/base/init_google.h"
#include "ortools/base/logging.h"
#include "ortools/linear_solver/linear_solver.h"
using namespace operations_research;
/**
* This method shows two ways to initialize a Xpress solver instance.
* Two environment variables are used to specify the Xpress installation paths:
* * XPRESSDIR : Path to the Xpress root directory containing bin and lib
* folders
* * XPRESS : Path to the directory containing Xpress license
*/
void useXpressSolver(bool solveAsMip, bool useFactory) {
std::unique_ptr<MPSolver> solver = nullptr;
if (useFactory) {
/* This is the preferred way as the program won't stop if anything went
wrong. In such a case, `solver` will take value `nullptr` */
std::string xpressName = (solveAsMip ? "XPRESS" : "XPRESS_LP");
solver.reset(MPSolver::CreateSolver(xpressName));
} else {
MPSolver::OptimizationProblemType problemType =
(solveAsMip ? MPSolver::XPRESS_MIXED_INTEGER_PROGRAMMING
: MPSolver::XPRESS_LINEAR_PROGRAMMING);
/* MPSolver::SupportsProblemType(problem_type) will test if Xpress is
correctly loaded and has a valid license. This check is important to keep
the program running if Xpress is not correctly installed. With the
constructor usage, if Xpress is badly loaded or if there is a problem
with the license, the program will abort (SIGABRT)
*/
if (MPSolver::SupportsProblemType(problemType)) {
solver.reset(new MPSolver("IntegerProgrammingExample", problemType));
}
}
if (solver == nullptr) {
LOG(WARNING) << "Xpress solver is not available";
return;
}
// Use the solver
/*
max -100 x1 + 10 x2
s.t. x2 <= 20 x1;
30 x1 + 3.5 x2 <= 350
0 <= x1 <= 5
0 <= x2
*/
const double infinity = MPSolver::infinity();
const MPVariable* x1 = solver->MakeIntVar(0, 5, "x1");
const MPVariable* x2 = solver->MakeNumVar(0.0, infinity, "x2");
MPObjective* const objective = solver->MutableObjective();
objective->SetCoefficient(x1, -100);
objective->SetCoefficient(x2, 10);
objective->SetMaximization();
MPConstraint* const c0 = solver->MakeRowConstraint(-infinity, 0.0);
c0->SetCoefficient(x1, -20.0);
c0->SetCoefficient(x2, 1);
MPConstraint* const c1 = solver->MakeRowConstraint(-infinity, 350.0);
c1->SetCoefficient(x1, 30.0);
c1->SetCoefficient(x2, 3.5);
const MPSolver::ResultStatus result_status = solver->Solve();
// Check that the problem has an optimal solution.
if (result_status != MPSolver::OPTIMAL) {
LOG(FATAL) << "Solver returned with non-optimal status.";
} else {
LOG(WARNING) << "Optimal solution found: obj=" << objective->Value();
}
}
#define ABSL_MIN_LOG_LEVEL INFO;
int main(int argc, char** argv) {
absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfo);
InitGoogle(argv[0], &argc, &argv, true);
std::cout << "start\n";
LOG(WARNING) << "start";
for (bool solveAsMip : {true, false}) {
for (bool useFactory : {true, false}) {
useXpressSolver(solveAsMip, useFactory);
}
}
return EXIT_SUCCESS;
}