Add AddHint to cpp and csharp, port hinting samples

makefiles/Makefile.cpp.mk

@@ -401,6 +401,7 @@ test_cc_sat_samples: \
  rcc_reified_sample_sat \
  rcc_search_for_all_solutions_sample_sat \
  rcc_simple_sat_program \
+ rcc_solution_hinting_sample_sat \
  rcc_solve_and_print_intermediate_solutions_sample_sat \
  rcc_solve_with_time_limit_sample_sat \
  rcc_step_function_sample_sat \

makefiles/Makefile.dotnet.mk

@@ -520,6 +520,7 @@ test_dotnet_sat_samples:
 	$(MAKE) run SOURCE=ortools/sat/samples/ReifiedSampleSat.cs
 	$(MAKE) run SOURCE=ortools/sat/samples/SearchForAllSolutionsSampleSat.cs
 	$(MAKE) run SOURCE=ortools/sat/samples/SimpleSatProgram.cs
+	$(MAKE) run SOURCE=ortools/sat/samples/SolutionHintingSampleSat.cs
 	$(MAKE) run SOURCE=ortools/sat/samples/SolveAndPrintIntermediateSolutionsSampleSat.cs
 	$(MAKE) run SOURCE=ortools/sat/samples/SolveWithTimeLimitSampleSat.cs
 	$(MAKE) run SOURCE=ortools/sat/samples/StepFunctionSampleSat.cs

ortools/sat/cp_model.cc

@@ -733,6 +733,11 @@ void CpModelBuilder::AddDecisionStrategy(
   proto->set_domain_reduction_strategy(domain_strategy);
 }
 
+void CpModelBuilder::AddHint(IntVar var, int64 value) {
+  cp_model_.mutable_solution_hint()->add_vars(GetOrCreateIntegerIndex(var.index_));
+  cp_model_.mutable_solution_hint()->add_values(value);
+}
+
 int64 SolutionIntegerValue(const CpSolverResponse& r, const LinearExpr& expr) {
   int64 result = expr.constant();
   for (int i = 0; i < expr.variables().size(); ++i) {

ortools/sat/cp_model.h

@@ -798,6 +798,9 @@ class CpModelBuilder {
       DecisionStrategyProto::VariableSelectionStrategy var_strategy,
       DecisionStrategyProto::DomainReductionStrategy domain_strategy);
 
+  /// Adds hinting to a variable.
+  void AddHint(IntVar var, int64 value);
+
   // TODO(user) : add MapDomain?
 
   const CpModelProto& Build() const { return Proto(); }

ortools/sat/csharp/CpModel.cs

@@ -635,6 +635,15 @@ namespace Google.OrTools.Sat
       model_.SearchStrategy.Add(ds);
     }
 
+    public void AddHint(IntVar var, long value)
+    {
+      if (model_.SolutionHint == null) {
+          model_.SolutionHint = new PartialVariableAssignment();
+      }
+      model_.SolutionHint.Vars.Add(var.GetIndex());
+      model_.SolutionHint.Values.Add(value);
+    }
+
     // Internal methods.
 
     void SetObjective(LinearExpr obj, bool minimize)

ortools/sat/samples/SolutionHintingSampleSat.cs

@@ -0,0 +1,91 @@
+// Copyright 2010-2018 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.
+
+// [START program]
+using System;
+using Google.OrTools.Sat;
+
+// [START print_solution]
+public class VarArraySolutionPrinter : CpSolverSolutionCallback
+{
+  public VarArraySolutionPrinter(IntVar[] variables)
+  {
+    variables_ = variables;
+  }
+
+  public override void OnSolutionCallback()
+  {
+    {
+      Console.WriteLine(String.Format("Solution #{0}: time = {1:F2} s",
+                                      solution_count_, WallTime()));
+      foreach (IntVar v in variables_)
+      {
+        Console.WriteLine(
+            String.Format("  {0} = {1}", v.ShortString(), Value(v)));
+      }
+      solution_count_++;
+    }
+  }
+
+  public int SolutionCount()
+  {
+    return solution_count_;
+  }
+
+  private int solution_count_;
+  private IntVar[] variables_;
+}
+// [END print_solution]
+
+public class SolutionHintingSampleSat
+{
+  static void Main()
+  {
+    // Creates the model.
+    // [START model]
+    CpModel model = new CpModel();
+    // [END model]
+
+    // Creates the variables.
+    // [START variables]
+    int num_vals = 3;
+
+    IntVar x = model.NewIntVar(0, num_vals - 1, "x");
+    IntVar y = model.NewIntVar(0, num_vals - 1, "y");
+    IntVar z = model.NewIntVar(0, num_vals - 1, "z");
+    // [END variables]
+
+    // Creates the constraints.
+    // [START constraints]
+    model.Add(x != y);
+    // [END constraints]
+
+    // Solution hinting: x <- 1, y <- 2
+    model.AddHint(x, 1);
+    model.AddHint(y, 2);
+
+    // [START objective]
+    model.Maximize(LinearExpr.ScalProd(new IntVar[] {x, y, z}, new int[] {1, 2, 3}));
+    // [END objective]
+
+    // Creates a solver and solves the model.
+    // [START solve]
+    CpSolver solver = new CpSolver();
+    VarArraySolutionPrinter cb =
+        new VarArraySolutionPrinter(new IntVar[] { x, y, z });
+    CpSolverStatus status = solver.SolveWithSolutionCallback(model, cb);
+    // [END solve]
+
+  }
+}
+// [END program]

ortools/sat/samples/SolutionHintingSampleSat.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <LangVersion>7.3</LangVersion>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <EnableDefaultItems>false</EnableDefaultItems>
+    <RestoreSources>../../../packages;$(RestoreSources);https://api.nuget.org/v3/index.json</RestoreSources>
+    <AssemblyName>Google.OrTools.SolutionHintingSampleSat</AssemblyName>
+    <IsPackable>true</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugType>full</DebugType>
+    <Optimize>true</Optimize>
+    <GenerateTailCalls>true</GenerateTailCalls>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="SolutionHintingSampleSat.cs" />
+    <PackageReference Include="Google.OrTools" Version="7.4.*" />
+  </ItemGroup>
+</Project>

ortools/sat/samples/solution_hinting_sample_sat.cc

@@ -0,0 +1,73 @@
+// Copyright 2010-2018 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.
+
+// [START program]
+#include "ortools/sat/cp_model.h"
+#include "ortools/sat/model.h"
+
+namespace operations_research {
+namespace sat {
+
+void SolutionHintingSampleSat() {
+  // [START model]
+  CpModelBuilder cp_model;
+  // [END model]
+
+  // [START variables]
+  const Domain domain(0, 2);
+  const IntVar x = cp_model.NewIntVar(domain).WithName("x");
+  const IntVar y = cp_model.NewIntVar(domain).WithName("y");
+  const IntVar z = cp_model.NewIntVar(domain).WithName("z");
+  // [END variables]
+
+  // [START constraints]
+  cp_model.AddNotEqual(x, y);
+  // [END constraints]
+
+  // [START objective]
+  cp_model.Maximize(LinearExpr::ScalProd({x, y, z}, {1, 2, 3}));
+  // [END objective]
+
+  // Solution hinting: x <- 1, y <- 2
+  cp_model.AddHint(x, 1);
+  cp_model.AddHint(y, 2);
+
+  // [START print_solution]
+  Model model;
+
+  int num_solutions = 0;
+  model.Add(NewFeasibleSolutionObserver([&](const CpSolverResponse& r) {
+    LOG(INFO) << "Solution " << num_solutions;
+    LOG(INFO) << "  x = " << SolutionIntegerValue(r, x);
+    LOG(INFO) << "  y = " << SolutionIntegerValue(r, y);
+    LOG(INFO) << "  z = " << SolutionIntegerValue(r, z);
+    num_solutions++;
+  }));
+  // [END print_solution]
+
+  // Solving part.
+  // [START solve]
+  const CpSolverResponse response = SolveCpModel(cp_model.Build(), &model);
+  LOG(INFO) << CpSolverResponseStats(response);
+  // [END solve]
+}
+
+}  // namespace sat
+}  // namespace operations_research
+
+int main() {
+  operations_research::sat::SolutionHintingSampleSat();
+
+  return EXIT_SUCCESS;
+}
+// [END program]