1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
/********************* */
/*! \file array_proof_reconstruction.cpp
** \verbatim
** Top contributors (to current version):
** Guy Katz, Tim King
** This file is part of the CVC4 project.
** Copyright (c) 2009-2019 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** [[ Add lengthier description here ]]
** \todo document this file
**/
#include "theory/arrays/array_proof_reconstruction.h"
#include <memory>
namespace CVC4 {
namespace theory {
namespace arrays {
ArrayProofReconstruction::ArrayProofReconstruction(const eq::EqualityEngine* equalityEngine)
: d_equalityEngine(equalityEngine) {
}
void ArrayProofReconstruction::setRowMergeTag(unsigned tag) {
d_reasonRow = tag;
}
void ArrayProofReconstruction::setRow1MergeTag(unsigned tag) {
d_reasonRow1 = tag;
}
void ArrayProofReconstruction::setExtMergeTag(unsigned tag) {
d_reasonExt = tag;
}
void ArrayProofReconstruction::notify(
unsigned reasonType, Node reason, Node a, Node b,
std::vector<TNode>& equalities, eq::EqProof* proof) const {
Debug("pf::array") << "ArrayProofReconstruction::notify( "
<< reason << ", " << a << ", " << b << std::endl;
if (reasonType == d_reasonExt) {
if (proof) {
// Todo: here we assume that a=b is an assertion. We should probably call
// explain() recursively, to explain this.
std::shared_ptr<eq::EqProof> childProof = std::make_shared<eq::EqProof>();
childProof->d_node = reason;
proof->d_children.push_back(childProof);
}
}
else if (reasonType == d_reasonRow) {
// ROW rules mean that (i==k) OR ((a[i]:=t)[k] == a[k])
// The equality here will be either (i == k) because ((a[i]:=t)[k] != a[k]),
// or ((a[i]:=t)[k] == a[k]) because (i != k).
if (proof) {
if (a.getKind() == kind::SELECT) {
// This is the case of ((a[i]:=t)[k] == a[k]) because (i != k).
// The edge is ((a[i]:=t)[k], a[k]), or (a[k], (a[i]:=t)[k]). This flag should be
// false in the first case and true in the second case.
bool currentNodeIsUnchangedArray;
Assert(a.getNumChildren() == 2);
Assert(b.getNumChildren() == 2);
if (a[0].getKind() == kind::VARIABLE || a[0].getKind() == kind::SKOLEM) {
currentNodeIsUnchangedArray = true;
} else if (b[0].getKind() == kind::VARIABLE || b[0].getKind() == kind::SKOLEM) {
currentNodeIsUnchangedArray = false;
} else {
Assert(a[0].getKind() == kind::STORE);
Assert(b[0].getKind() == kind::STORE);
if (a[0][0] == b[0]) {
currentNodeIsUnchangedArray = false;
} else if (b[0][0] == a[0]) {
currentNodeIsUnchangedArray = true;
} else {
Unreachable();
}
}
Node indexOne = currentNodeIsUnchangedArray ? a[1] : a[0][1];
Node indexTwo = currentNodeIsUnchangedArray ? b[0][1] : b[1];
// Some assertions to ensure that the theory of arrays behaves as expected
Assert(a[1] == b[1]);
if (currentNodeIsUnchangedArray) {
Assert(a[0] == b[0][0]);
} else {
Assert(a[0][0] == b[0]);
}
Debug("pf::ee") << "Getting explanation for ROW guard: "
<< indexOne << " != " << indexTwo << std::endl;
std::shared_ptr<eq::EqProof> childProof =
std::make_shared<eq::EqProof>();
d_equalityEngine->explainEquality(indexOne, indexTwo, false, equalities,
childProof.get());
// It could be that the guard condition is a constant disequality. In
// this case, we need to change it to a different format.
bool haveNegChild = false;
for (unsigned i = 0; i < childProof->d_children.size(); ++i) {
if (childProof->d_children[i]->d_node.getKind() == kind::NOT)
haveNegChild = true;
}
if ((childProof->d_children.size() != 0) &&
(childProof->d_id == theory::eq::MERGED_THROUGH_CONSTANTS || !haveNegChild)) {
// The proof has two children, explaining why each index is a (different) constant.
Assert(childProof->d_children.size() == 2);
Node constantOne, constantTwo;
// Each subproof explains why one of the indices is constant.
if (childProof->d_children[0]->d_id == theory::eq::MERGED_THROUGH_REFLEXIVITY) {
constantOne = childProof->d_children[0]->d_node;
} else {
Assert(childProof->d_children[0]->d_node.getKind() == kind::EQUAL);
if ((childProof->d_children[0]->d_node[0] == indexOne) ||
(childProof->d_children[0]->d_node[0] == indexTwo)) {
constantOne = childProof->d_children[0]->d_node[1];
} else {
constantOne = childProof->d_children[0]->d_node[0];
}
}
if (childProof->d_children[1]->d_id == theory::eq::MERGED_THROUGH_REFLEXIVITY) {
constantTwo = childProof->d_children[1]->d_node;
} else {
Assert(childProof->d_children[1]->d_node.getKind() == kind::EQUAL);
if ((childProof->d_children[1]->d_node[0] == indexOne) ||
(childProof->d_children[1]->d_node[0] == indexTwo)) {
constantTwo = childProof->d_children[1]->d_node[1];
} else {
constantTwo = childProof->d_children[1]->d_node[0];
}
}
std::shared_ptr<eq::EqProof> constantDisequalityProof =
std::make_shared<eq::EqProof>();
constantDisequalityProof->d_id = theory::eq::MERGED_THROUGH_CONSTANTS;
constantDisequalityProof->d_node =
NodeManager::currentNM()->mkNode(kind::EQUAL, constantOne, constantTwo).negate();
// Middle is where we need to insert the new disequality
std::vector<std::shared_ptr<eq::EqProof>>::iterator middle =
childProof->d_children.begin();
++middle;
childProof->d_children.insert(middle, constantDisequalityProof);
childProof->d_id = theory::eq::MERGED_THROUGH_TRANS;
childProof->d_node =
NodeManager::currentNM()->mkNode(kind::EQUAL, indexOne, indexTwo).negate();
}
proof->d_children.push_back(childProof);
} else {
// This is the case of (i == k) because ((a[i]:=t)[k] != a[k]),
Node indexOne = a;
Node indexTwo = b;
Debug("pf::ee") << "The two indices are: " << indexOne << ", " << indexTwo << std::endl
<< "The reason for the edge is: " << reason << std::endl;
Assert(reason.getNumChildren() == 2);
Debug("pf::ee") << "Getting explanation for ROW guard: " << reason[1] << std::endl;
std::shared_ptr<eq::EqProof> childProof =
std::make_shared<eq::EqProof>();
d_equalityEngine->explainEquality(reason[1][0], reason[1][1], false,
equalities, childProof.get());
proof->d_children.push_back(childProof);
}
}
}
else if (reasonType == d_reasonRow1) {
// No special handling required at this time
}
}
}/* CVC4::theory::arrays namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
|
