basic_example.py

#!/usr/bin/env python3
# Copyright 2010-2022 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.
"""Minimal example to call the GLOP solver."""
# [START program]
# [START import]
from ortools.linear_solver import pywraplp
from ortools.init import pywrapinit
# [END import]


def main():
    # [START solver]
    # Create the linear solver with the GLOP backend.
    solver = pywraplp.Solver.CreateSolver('GLOP')
    if not solver:
        return
    # [END solver]

    # [START variables]
    # Create the variables x and y.
    x = solver.NumVar(0, 1, 'x')
    y = solver.NumVar(0, 2, 'y')

    print('Number of variables =', solver.NumVariables())
    # [END variables]

    # [START constraints]
    # Create a linear constraint, 0 <= x + y <= 2.
    ct = solver.Constraint(0, 2, 'ct')
    ct.SetCoefficient(x, 1)
    ct.SetCoefficient(y, 1)

    print('Number of constraints =', solver.NumConstraints())
    # [END constraints]

    # [START objective]
    # Create the objective function, 3 * x + y.
    objective = solver.Objective()
    objective.SetCoefficient(x, 3)
    objective.SetCoefficient(y, 1)
    objective.SetMaximization()
    # [END objective]

    # [START solve]
    solver.Solve()
    # [END solve]

    # [START print_solution]
    print('Solution:')
    print('Objective value =', objective.Value())
    print('x =', x.solution_value())
    print('y =', y.solution_value())
    # [END print_solution]


if __name__ == '__main__':
    pywrapinit.CppBridge.InitLogging('basic_example.py')
    cpp_flags = pywrapinit.CppFlags()
    cpp_flags.logtostderr = True
    cpp_flags.log_prefix = False
    pywrapinit.CppBridge.SetFlags(cpp_flags)

    main()
# [END program]