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sat_proto_solver.cc
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sat_proto_solver.cc
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// 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.
#include "ortools/linear_solver/sat_proto_solver.h"
#include <vector>
#include "ortools/linear_solver/linear_solver.pb.h"
#include "ortools/linear_solver/model_validator.h"
#include "ortools/linear_solver/sat_solver_utils.h"
#include "ortools/port/proto_utils.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/sat/cp_model_solver.h"
#include "ortools/sat/lp_utils.h"
#include "ortools/sat/sat_parameters.pb.h"
#include "ortools/util/time_limit.h"
namespace operations_research {
namespace {
#if defined(PROTOBUF_INTERNAL_IMPL)
using google::protobuf::Message;
#else
using google::protobuf::Message;
#endif
MPSolverResponseStatus ToMPSolverResponseStatus(sat::CpSolverStatus status,
bool has_objective) {
switch (status) {
case sat::CpSolverStatus::UNKNOWN:
return MPSOLVER_NOT_SOLVED;
case sat::CpSolverStatus::MODEL_INVALID:
return MPSOLVER_MODEL_INVALID;
case sat::CpSolverStatus::FEASIBLE:
return has_objective ? MPSOLVER_FEASIBLE : MPSOLVER_OPTIMAL;
case sat::CpSolverStatus::INFEASIBLE:
return MPSOLVER_INFEASIBLE;
case sat::CpSolverStatus::OPTIMAL:
return MPSOLVER_OPTIMAL;
default: {
}
}
return MPSOLVER_ABNORMAL;
}
} // namespace
util::StatusOr<MPSolutionResponse> SatSolveProto(
MPModelRequest request, std::atomic<bool>* interrupt_solve) {
// By default, we use 8 threads as it allows to try a good set of orthogonal
// parameters. This can be overridden by the user.
sat::SatParameters params;
params.set_num_search_workers(8);
params.set_log_search_progress(request.enable_internal_solver_output());
if (request.has_solver_specific_parameters()) {
// If code is compiled with proto-lite runtime, `solver_specific_parameters`
// should be encoded as non-human readable string from `SerializeAsString`.
if (!std::is_base_of<Message, sat::SatParameters>::value) {
CHECK(params.MergeFromString(request.solver_specific_parameters()));
} else {
ProtobufTextFormatMergeFromString(request.solver_specific_parameters(),
¶ms);
}
}
if (request.has_solver_time_limit_seconds()) {
params.set_max_time_in_seconds(
static_cast<double>(request.solver_time_limit_seconds()) / 1000.0);
}
MPSolutionResponse response;
if (!ExtractValidMPModelInPlaceOrPopulateResponseStatus(&request,
&response)) {
if (params.log_search_progress()) {
// This is needed for our benchmark scripts.
sat::CpSolverResponse cp_response;
cp_response.set_status(sat::CpSolverStatus::MODEL_INVALID);
LOG(INFO) << CpSolverResponseStats(cp_response);
}
return response;
}
MPModelProto* const mp_model = request.mutable_model();
std::unique_ptr<glop::ShiftVariableBoundsPreprocessor>
shift_bounds_preprocessor;
const auto status =
ApplyMipPresolveSteps(mp_model, &shift_bounds_preprocessor);
if (status == MPSolverResponseStatus::MPSOLVER_INFEASIBLE) {
if (params.log_search_progress()) {
// This is needed for our benchmark scripts.
sat::CpSolverResponse cp_response;
cp_response.set_status(sat::CpSolverStatus::INFEASIBLE);
LOG(INFO) << CpSolverResponseStats(cp_response);
}
response.set_status(MPSolverResponseStatus::MPSOLVER_INFEASIBLE);
response.set_status_str("Problem proven infeasible during MIP presolve");
return response;
}
const std::vector<double> var_scaling =
sat::ScaleContinuousVariables(params.mip_var_scaling(), mp_model);
sat::CpModelProto cp_model;
if (!ConvertMPModelProtoToCpModelProto(params, *mp_model, &cp_model)) {
if (params.log_search_progress()) {
// This is needed for our benchmark scripts.
sat::CpSolverResponse cp_response;
cp_response.set_status(sat::CpSolverStatus::MODEL_INVALID);
LOG(INFO) << CpSolverResponseStats(cp_response);
}
response.set_status(MPSOLVER_MODEL_INVALID);
response.set_status_str("Failed to convert model into CP-SAT model");
return response;
}
DCHECK_EQ(cp_model.variables().size(), var_scaling.size());
DCHECK_EQ(cp_model.variables().size(), mp_model->variable().size());
// Copy and scale the hint if there is one. Note that we need to shift it
// accordingly if we shifted the domains of the variables.
if (request.model().has_solution_hint()) {
auto* cp_model_hint = cp_model.mutable_solution_hint();
const int size = request.model().solution_hint().var_index().size();
glop::DenseRow offsets(glop::ColIndex(size), 0.0);
if (shift_bounds_preprocessor != nullptr) {
offsets = shift_bounds_preprocessor->offsets();
}
for (int i = 0; i < size; ++i) {
const int var = request.model().solution_hint().var_index(i);
if (var >= var_scaling.size()) continue;
cp_model_hint->add_vars(var);
cp_model_hint->add_values(static_cast<int64>(
std::round((request.model().solution_hint().var_value(i) -
offsets[glop::ColIndex(i)]) *
var_scaling[var])));
}
}
// We no longer need the request. Reclaim its memory.
const int num_vars = mp_model->variable_size();
request.Clear();
// Solve.
sat::Model sat_model;
sat_model.Add(NewSatParameters(params));
if (interrupt_solve != nullptr) {
sat_model.GetOrCreate<TimeLimit>()->RegisterExternalBooleanAsLimit(
interrupt_solve);
}
const sat::CpSolverResponse cp_response =
sat::SolveCpModel(cp_model, &sat_model);
// Convert the response.
//
// TODO(user): Implement the row and column status.
response.set_status(
ToMPSolverResponseStatus(cp_response.status(), cp_model.has_objective()));
if (response.status() == MPSOLVER_FEASIBLE ||
response.status() == MPSOLVER_OPTIMAL) {
response.set_objective_value(cp_response.objective_value());
response.set_best_objective_bound(cp_response.best_objective_bound());
// Postsolve the bound shift and scaling.
glop::ProblemSolution solution(glop::RowIndex(0), glop::ColIndex(num_vars));
for (int v = 0; v < num_vars; ++v) {
solution.primal_values[glop::ColIndex(v)] =
static_cast<double>(cp_response.solution(v)) / var_scaling[v];
}
if (shift_bounds_preprocessor) {
shift_bounds_preprocessor->RecoverSolution(&solution);
}
for (int v = 0; v < num_vars; ++v) {
response.add_variable_value(solution.primal_values[glop::ColIndex(v)]);
}
}
return response;
}
} // namespace operations_research