1 // Copyright 2010-2021 Google LLC
2 // Licensed under the Apache License, Version 2.0 (the "License");
3 // you may not use this file except in compliance with the License.
4 // You may obtain a copy of the License at
5 //
6 // http://www.apache.org/licenses/LICENSE-2.0
7 //
8 // Unless required by applicable law or agreed to in writing, software
9 // distributed under the License is distributed on an "AS IS" BASIS,
10 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11 // See the License for the specific language governing permissions and
12 // limitations under the License.
13
14 #include "ortools/sat/drat_proof_handler.h"
15
16 #include <algorithm>
17
18 #include "absl/memory/memory.h"
19 #include "ortools/base/int_type.h"
20 #include "ortools/base/logging.h"
21 #include "ortools/base/strong_vector.h"
22
23 namespace operations_research {
24 namespace sat {
25
DratProofHandler()26 DratProofHandler::DratProofHandler()
27 : variable_index_(0), drat_checker_(new DratChecker()) {}
28
DratProofHandler(bool in_binary_format,File * output,bool check)29 DratProofHandler::DratProofHandler(bool in_binary_format, File* output,
30 bool check)
31 : variable_index_(0),
32 drat_writer_(new DratWriter(in_binary_format, output)) {
33 if (check) {
34 drat_checker_ = absl::make_unique<DratChecker>();
35 }
36 }
37
ApplyMapping(const absl::StrongVector<BooleanVariable,BooleanVariable> & mapping)38 void DratProofHandler::ApplyMapping(
39 const absl::StrongVector<BooleanVariable, BooleanVariable>& mapping) {
40 absl::StrongVector<BooleanVariable, BooleanVariable> new_mapping;
41 for (BooleanVariable v(0); v < mapping.size(); ++v) {
42 const BooleanVariable image = mapping[v];
43 if (image != kNoBooleanVariable) {
44 if (image >= new_mapping.size())
45 new_mapping.resize(image.value() + 1, kNoBooleanVariable);
46 CHECK_EQ(new_mapping[image], kNoBooleanVariable);
47 new_mapping[image] =
48 v < reverse_mapping_.size() ? reverse_mapping_[v] : v;
49 CHECK_NE(new_mapping[image], kNoBooleanVariable);
50 }
51 }
52 std::swap(new_mapping, reverse_mapping_);
53 }
54
SetNumVariables(int num_variables)55 void DratProofHandler::SetNumVariables(int num_variables) {
56 CHECK_GE(num_variables, reverse_mapping_.size());
57 while (reverse_mapping_.size() < num_variables) {
58 reverse_mapping_.push_back(BooleanVariable(variable_index_++));
59 }
60 }
61
AddOneVariable()62 void DratProofHandler::AddOneVariable() {
63 reverse_mapping_.push_back(BooleanVariable(variable_index_++));
64 }
65
AddProblemClause(absl::Span<const Literal> clause)66 void DratProofHandler::AddProblemClause(absl::Span<const Literal> clause) {
67 if (drat_checker_ != nullptr) {
68 drat_checker_->AddProblemClause(clause);
69 }
70 }
71
AddClause(absl::Span<const Literal> clause)72 void DratProofHandler::AddClause(absl::Span<const Literal> clause) {
73 MapClause(clause);
74 if (drat_checker_ != nullptr) {
75 drat_checker_->AddInferedClause(values_);
76 }
77 if (drat_writer_ != nullptr) {
78 drat_writer_->AddClause(values_);
79 }
80 }
81
DeleteClause(absl::Span<const Literal> clause)82 void DratProofHandler::DeleteClause(absl::Span<const Literal> clause) {
83 MapClause(clause);
84 if (drat_checker_ != nullptr) {
85 drat_checker_->DeleteClause(values_);
86 }
87 if (drat_writer_ != nullptr) {
88 drat_writer_->DeleteClause(values_);
89 }
90 }
91
Check(double max_time_in_seconds)92 DratChecker::Status DratProofHandler::Check(double max_time_in_seconds) {
93 if (drat_checker_ != nullptr) {
94 // The empty clause is not explicitly added by the solver.
95 drat_checker_->AddInferedClause({});
96 return drat_checker_->Check(max_time_in_seconds);
97 }
98 return DratChecker::Status::UNKNOWN;
99 }
100
MapClause(absl::Span<const Literal> clause)101 void DratProofHandler::MapClause(absl::Span<const Literal> clause) {
102 values_.clear();
103 for (const Literal l : clause) {
104 CHECK_LT(l.Variable(), reverse_mapping_.size());
105 const Literal original_literal =
106 Literal(reverse_mapping_[l.Variable()], l.IsPositive());
107 values_.push_back(original_literal);
108 }
109
110 // The sorting is such that new variables appear first. This is important for
111 // BVA since DRAT-trim only check the RAT property with respect to the first
112 // variable of the clause.
113 std::sort(values_.begin(), values_.end(), [](Literal a, Literal b) {
114 return std::abs(a.SignedValue()) > std::abs(b.SignedValue());
115 });
116 }
117
118 } // namespace sat
119 } // namespace operations_research
120