96 lines
3.2 KiB
C++
96 lines
3.2 KiB
C++
// Copyright 2010-2025 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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#include <stdlib.h>
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#include "absl/base/log_severity.h"
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#include "absl/log/globals.h"
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#include "absl/types/span.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/sat/cp_model.h"
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#include "ortools/sat/cp_model.pb.h"
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#include "ortools/sat/cp_model_solver.h"
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#include "ortools/sat/model.h"
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#include "ortools/sat/sat_parameters.pb.h"
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#include "ortools/util/sorted_interval_list.h"
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namespace operations_research {
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namespace sat {
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void StepFunctionSampleSat() {
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// Create the CP-SAT model.
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CpModelBuilder cp_model;
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// Declare our primary variable.
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const IntVar x = cp_model.NewIntVar({0, 20});
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// Create the expression variable and implement the step function
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// Note it is not defined for var == 2.
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//
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// - 3
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// -- -- --------- 2
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// 1
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// -- --- 0
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// 0 ================ 20
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//
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IntVar expr = cp_model.NewIntVar({0, 3});
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// expr == 0 on [5, 6] U [8, 10]
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BoolVar b0 = cp_model.NewBoolVar();
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cp_model.AddLinearConstraint(x, Domain::FromValues({5, 6, 8, 9, 10}))
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.OnlyEnforceIf(b0);
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cp_model.AddEquality(expr, 0).OnlyEnforceIf(b0);
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// expr == 2 on [0, 1] U [3, 4] U [11, 20]
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BoolVar b2 = cp_model.NewBoolVar();
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cp_model
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.AddLinearConstraint(x, Domain::FromIntervals({{0, 1}, {3, 4}, {11, 20}}))
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.OnlyEnforceIf(b2);
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cp_model.AddEquality(expr, 2).OnlyEnforceIf(b2);
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// expr == 3 when x = 7
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BoolVar b3 = cp_model.NewBoolVar();
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cp_model.AddEquality(x, 7).OnlyEnforceIf(b3);
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cp_model.AddEquality(expr, 3).OnlyEnforceIf(b3);
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// At least one bi is true. (we could use an exactly one constraint).
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cp_model.AddBoolOr({b0, b2, b3});
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// Search for x values in increasing order.
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cp_model.AddDecisionStrategy({x}, DecisionStrategyProto::CHOOSE_FIRST,
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DecisionStrategyProto::SELECT_MIN_VALUE);
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// Create a solver and solve with a fixed search.
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Model model;
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SatParameters parameters;
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parameters.set_search_branching(SatParameters::FIXED_SEARCH);
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parameters.set_enumerate_all_solutions(true);
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model.Add(NewSatParameters(parameters));
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model.Add(NewFeasibleSolutionObserver([&](const CpSolverResponse& r) {
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LOG(INFO) << "x=" << SolutionIntegerValue(r, x) << " expr"
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<< SolutionIntegerValue(r, expr);
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}));
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SolveCpModel(cp_model.Build(), &model);
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}
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} // namespace sat
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} // namespace operations_research
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int main(int argc, char* argv[]) {
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InitGoogle(argv[0], &argc, &argv, true);
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absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfo);
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operations_research::sat::StepFunctionSampleSat();
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return EXIT_SUCCESS;
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}
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