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schedulers/tetrisched/include/tetrisched/GoogleCPSolver.hpp
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| #ifndef _TETRISCHED_GOOGLE_CP_SOLVER_HPP_ | ||
| #define _TETRISCHED_GOOGLE_CP_SOLVER_HPP_ | ||
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| #include <variant> | ||
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| #include "ortools/sat/cp_model.h" | ||
| #include "tetrisched/Solver.hpp" | ||
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| namespace tetrisched { | ||
| // Import the relevant names from the ORTools namespace. | ||
| using operations_research::sat::BoolVar; | ||
| using operations_research::sat::CpModelBuilder; | ||
| using operations_research::sat::IntVar; | ||
| using operations_research::sat::LinearExpr; | ||
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| class GoogleCPSolver : public Solver { | ||
| using GoogleCPVarType = std::variant<IntVar, BoolVar>; | ||
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| private: | ||
| /// The SolverModelPtr associated with this GoogleCPSolver. | ||
| SolverModelPtr solverModel; | ||
| /// The ORTools model associated with this GoogleCPSolver. | ||
| std::unique_ptr<CpModelBuilder> cpModel; | ||
| /// A map from the Variable ID to the ORTools variable. | ||
| std::unordered_map<uint32_t, GoogleCPVarType> cpVariables; | ||
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| /// Translates the VariablePtr into an IntVar / BoolVar. | ||
| GoogleCPVarType translateVariable(const VariablePtr& variable) const; | ||
| /// Translates the ConstraintPtr into a Constraint and adds it to the model. | ||
| operations_research::sat::Constraint translateConstraint( | ||
| const ConstraintPtr& constraint); | ||
| /// Translates the ObjectiveFunctionPtr into an Expression in Google OR-Tools. | ||
| LinearExpr translateObjectiveFunction( | ||
| const ObjectiveFunctionPtr& objectiveFunction) const; | ||
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| public: | ||
| /// Create a new CP-SAT solver. | ||
| GoogleCPSolver(); | ||
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| /// Retrieve a pointer to the SolverModel. | ||
| SolverModelPtr getModel() override; | ||
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| /// Translates the SolverModel into a CP-SAT model. | ||
| void translateModel() override; | ||
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| /// Export the constructed model to the given file. | ||
| void exportModel(const std::string& fileName) override; | ||
| }; | ||
| } // namespace tetrisched | ||
| #endif // _TETRISCHED_GOOGLE_CP_SOLVER_HPP_ |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,165 @@ | ||
| #include "tetrisched/GoogleCPSolver.hpp" | ||
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| namespace tetrisched { | ||
| GoogleCPSolver::GoogleCPSolver() : cpModel(new CpModelBuilder()) {} | ||
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| SolverModelPtr GoogleCPSolver::getModel() { | ||
| if (!solverModel) { | ||
| solverModel = std::shared_ptr<SolverModel>(new SolverModel()); | ||
| } | ||
| return solverModel; | ||
| } | ||
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| GoogleCPSolver::GoogleCPVarType GoogleCPSolver::translateVariable( | ||
| const VariablePtr& variable) const { | ||
| // Check that a continuous variable is not passed in. | ||
| if (variable->variableType == VariableType::VAR_CONTINUOUS) { | ||
| throw exceptions::SolverException( | ||
| "Cannot construct a continuous variable in ORTools."); | ||
| } else if (variable->variableType == VariableType::VAR_INTEGER) { | ||
| // Check that the Variable has been given both a lower and an upper bound. | ||
| // This is required to set a Domain in ORTools. | ||
| if (!(variable->lowerBound.has_value() && | ||
| variable->upperBound.has_value())) { | ||
| throw exceptions::SolverException( | ||
| "Cannot construct a variable without a lower and upper bound in " | ||
| "ORTools: " + | ||
| variable->toString()); | ||
| } | ||
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| // Construct the domain for the variable. | ||
| const operations_research::Domain domain(variable->lowerBound.value(), | ||
| variable->upperBound.value()); | ||
| return cpModel->NewIntVar(domain).WithName(variable->variableName); | ||
| } else if (variable->variableType == VariableType::VAR_INDICATOR) { | ||
| // Construct the Indicator variable. | ||
| return cpModel->NewBoolVar().WithName(variable->variableName); | ||
| } else { | ||
| throw exceptions::SolverException("Cannot construct a variable of type " + | ||
| std::to_string(variable->variableType) + | ||
| " in ORTools."); | ||
| } | ||
| } | ||
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| operations_research::sat::Constraint GoogleCPSolver::translateConstraint( | ||
| const ConstraintPtr& constraint) { | ||
| // TODO (Sukrit): We are currently assuming that all constraints and | ||
| // objectives are linear. We may need to support quadratic constraints. | ||
| operations_research::sat::LinearExpr constraintExpr; | ||
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| // Construct all the terms. | ||
| for (const auto& [coefficient, variable] : constraint->terms) { | ||
| if (variable) { | ||
| switch (variable->variableType) { | ||
| case VariableType::VAR_INTEGER: | ||
| constraintExpr += | ||
| coefficient * std::get<IntVar>(cpVariables.at(variable->getId())); | ||
| break; | ||
| case VariableType::VAR_INDICATOR: | ||
| constraintExpr += | ||
| coefficient * | ||
| std::get<BoolVar>(cpVariables.at(variable->getId())); | ||
| break; | ||
| default: | ||
| throw exceptions::SolverException( | ||
| "Cannot construct a constraint with a variable of type " + | ||
| std::to_string(variable->variableType) + " in ORTools."); | ||
| } | ||
| } else { | ||
| constraintExpr += coefficient; | ||
| } | ||
| } | ||
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| // Translate the constraint. | ||
| switch (constraint->constraintType) { | ||
| case ConstraintType::CONSTR_EQ: | ||
| return cpModel->AddEquality(constraintExpr, constraint->rightHandSide) | ||
| .WithName(constraint->getName()); | ||
| case ConstraintType::CONSTR_GE: | ||
| return cpModel | ||
| ->AddGreaterOrEqual(constraintExpr, constraint->rightHandSide) | ||
| .WithName(constraint->getName()); | ||
| case ConstraintType::CONSTR_LE: | ||
| return cpModel->AddLessOrEqual(constraintExpr, constraint->rightHandSide) | ||
| .WithName(constraint->getName()); | ||
| default: | ||
| throw exceptions::SolverException( | ||
| "Invalid constraint type: " + | ||
| std::to_string(constraint->constraintType)); | ||
| } | ||
| } | ||
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| LinearExpr GoogleCPSolver::translateObjectiveFunction( | ||
| const ObjectiveFunctionPtr& objectiveFunction) const { | ||
| LinearExpr objectiveExpr; | ||
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| // Construct all the terms. | ||
| for (const auto& [coefficient, variable] : objectiveFunction->terms) { | ||
| if (variable) { | ||
| switch (variable->variableType) { | ||
| case VariableType::VAR_INTEGER: | ||
| objectiveExpr += | ||
| coefficient * std::get<IntVar>(cpVariables.at(variable->getId())); | ||
| break; | ||
| case VariableType::VAR_INDICATOR: | ||
| objectiveExpr += coefficient * | ||
| std::get<BoolVar>(cpVariables.at(variable->getId())); | ||
| break; | ||
| default: | ||
| throw exceptions::SolverException( | ||
| "Cannot construct an objective function with a variable of " | ||
| "type " + | ||
| std::to_string(variable->variableType) + " in ORTools."); | ||
| } | ||
| } else { | ||
| objectiveExpr += coefficient; | ||
| } | ||
| } | ||
| return objectiveExpr; | ||
| } | ||
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| void GoogleCPSolver::translateModel() { | ||
| if (!solverModel) { | ||
| throw tetrisched::exceptions::SolverException( | ||
| "Empty SolverModel for GurobiSolver. Nothing to translate!"); | ||
| } | ||
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| // Generate all the variables and keep a cache of the variable indices | ||
| // to the ORTools variables. | ||
| for (const auto& [variableId, variable] : solverModel->variables) { | ||
| TETRISCHED_DEBUG("Adding variable " << variable->getName() << "(" | ||
| << variable->getId() | ||
| << ") to ORTools model."); | ||
| cpVariables[variableId] = translateVariable(variable); | ||
| } | ||
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| // Generate all the constraints. | ||
| for (const auto& [constraintId, constraint] : solverModel->constraints) { | ||
| TETRISCHED_DEBUG("Adding constraint " << constraint->getName() << "(" | ||
| << constraint->getId() | ||
| << ") to ORTools model."); | ||
| auto _ = translateConstraint(constraint); | ||
| } | ||
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| // Translate the objective function. | ||
| auto objectiveExpr = | ||
| translateObjectiveFunction(solverModel->objectiveFunction); | ||
| switch (solverModel->objectiveFunction->objectiveType) { | ||
| case ObjectiveType::OBJ_MINIMIZE: | ||
| cpModel->Minimize(objectiveExpr); | ||
| break; | ||
| case ObjectiveType::OBJ_MAXIMIZE: | ||
| cpModel->Maximize(objectiveExpr); | ||
| break; | ||
| default: | ||
| throw exceptions::SolverException( | ||
| "Invalid objective type: " + | ||
| std::to_string(solverModel->objectiveFunction->objectiveType)); | ||
| } | ||
| } | ||
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| void GoogleCPSolver::exportModel(const std::string& fileName) { | ||
| cpModel->ExportToFile(fileName); | ||
| } | ||
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| } // namespace tetrisched |
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