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
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
|
/********************* */
/*! \file bv_subtheory_algebraic.h
** \verbatim
** Top contributors (to current version):
** Liana Hadarean, Mathias Preiner, Tim King
** This file is part of the CVC4 project.
** Copyright (c) 2009-2018 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
**
** \brief Algebraic solver.
**
** Algebraic solver.
**/
#include "cvc4_private.h"
#pragma once
#include <unordered_map>
#include <unordered_set>
#include "theory/bv/bv_subtheory.h"
#include "theory/bv/slicer.h"
#include "theory/substitutions.h"
namespace CVC4 {
namespace theory {
namespace bv {
class AlgebraicSolver;
Node mergeExplanations(TNode expl1, TNode expl2);
Node mergeExplanations(const std::vector<Node>& expls);
/**
* Non-context dependent substitution with explanations.
*
*/
class SubstitutionEx {
struct SubstitutionElement {
Node to;
Node reason;
SubstitutionElement()
: to()
, reason()
{}
SubstitutionElement(TNode t, TNode r)
: to(t)
, reason(r)
{}
};
struct SubstitutionStackElement {
TNode node;
bool childrenAdded;
SubstitutionStackElement(TNode n, bool ca = false)
: node(n)
, childrenAdded(ca)
{}
};
typedef std::unordered_map<Node, SubstitutionElement, NodeHashFunction> Substitutions;
typedef std::unordered_map<Node, SubstitutionElement, NodeHashFunction> SubstitutionsCache;
Substitutions d_substitutions;
SubstitutionsCache d_cache;
bool d_cacheInvalid;
theory::SubstitutionMap* d_modelMap;
Node getReason(TNode node) const;
bool hasCache(TNode node) const;
Node getCache(TNode node) const;
void storeCache(TNode from, TNode to, Node rason);
Node internalApply(TNode node);
public:
SubstitutionEx(theory::SubstitutionMap* modelMap);
/**
* Returnst true if the substitution map did not contain from.
*
* @param from
* @param to
* @param reason
*
* @return
*/
bool addSubstitution(TNode from, TNode to, TNode reason);
Node apply(TNode node);
Node explain(TNode node) const;
};
/**
* In-processing worklist element, id keeps track of
* original assertion.
*
*/
struct WorklistElement {
Node node;
unsigned id;
WorklistElement(Node n, unsigned i) : node(n), id(i) {}
WorklistElement() : node(), id(-1) {}
};
typedef std::unordered_map<Node, Node, NodeHashFunction> NodeNodeMap;
typedef std::unordered_map<Node, unsigned, NodeHashFunction> NodeIdMap;
typedef std::unordered_set<TNode, TNodeHashFunction> TNodeSet;
class ExtractSkolemizer {
struct Extract {
unsigned high;
unsigned low;
Extract(unsigned h, unsigned l) : high(h), low(l) {}
};
struct ExtractList {
Base base;
std::vector<Extract> extracts;
ExtractList(unsigned bitwidth) : base(bitwidth), extracts() {}
ExtractList() : base(1), extracts() {}
void addExtract(Extract& e);
};
typedef std::unordered_map<Node, ExtractList, NodeHashFunction> VarExtractMap;
context::Context d_emptyContext;
VarExtractMap d_varToExtract;
theory::SubstitutionMap* d_modelMap;
theory::SubstitutionMap d_skolemSubst;
theory::SubstitutionMap d_skolemSubstRev;
void storeSkolem(TNode node, TNode skolem);
void storeExtract(TNode var, unsigned high, unsigned low);
void collectExtracts(TNode node, TNodeSet& seen);
Node skolemize(TNode);
Node unSkolemize(TNode);
Node mkSkolem(Node node);
public:
ExtractSkolemizer(theory::SubstitutionMap* modelMap);
void skolemize(std::vector<WorklistElement>&);
void unSkolemize(std::vector<WorklistElement>&);
~ExtractSkolemizer();
};
class BVQuickCheck;
class QuickXPlain;
/**
* AlgebraicSolver
*/
class AlgebraicSolver : public SubtheorySolver {
struct Statistics {
IntStat d_numCallstoCheck;
IntStat d_numSimplifiesToTrue;
IntStat d_numSimplifiesToFalse;
IntStat d_numUnsat;
IntStat d_numSat;
IntStat d_numUnknown;
TimerStat d_solveTime;
BackedStat<double> d_useHeuristic;
Statistics();
~Statistics();
};
std::unique_ptr<SubstitutionMap> d_modelMap;
std::unique_ptr<BVQuickCheck> d_quickSolver;
context::CDO<bool> d_isComplete;
context::CDO<bool> d_isDifficult; /**< flag to indicate whether the current assertions contain expensive BV operators */
unsigned long d_budget;
std::vector<Node> d_explanations; /**< explanations for assertions indexed by assertion id */
TNodeSet d_inputAssertions; /**< assertions in current context (for debugging purposes only) */
NodeIdMap d_ids; /**< map from assertions to ids */
uint64_t d_numSolved;
uint64_t d_numCalls;
/** separate quickXplain module as it can reuse the current SAT solver */
std::unique_ptr<QuickXPlain> d_quickXplain;
Statistics d_statistics;
bool useHeuristic();
void setConflict(TNode conflict);
bool isSubstitutableIn(TNode node, TNode in);
bool checkExplanation(TNode expl);
void storeExplanation(TNode expl);
void storeExplanation(unsigned id, TNode expl);
/**
* Apply substitutions and rewriting to the worklist assertions to a fixpoint.
* Subsitutions learned store in subst.
*
* @param worklist
* @param subst
*/
void processAssertions(std::vector<WorklistElement>& worklist, SubstitutionEx& subst);
/**
* Attempt to solve the equation in fact, and if successful
* add a substitution to subst.
*
* @param fact equation we are trying to solve
* @param reason the reason in terms of original assertions
* @param subst substitution map
*
* @return true if added a substitution to subst
*/
bool solve(TNode fact, TNode reason, SubstitutionEx& subst);
/**
* Run a SAT solver on the given facts with the given budget.
* Sets the isComplete flag and conflict accordingly.
*
* @param facts
*
* @return true if no conflict was detected.
*/
bool quickCheck(std::vector<Node>& facts);
public:
AlgebraicSolver(context::Context* c, TheoryBV* bv);
~AlgebraicSolver();
void preRegister(TNode node) override {}
bool check(Theory::Effort e) override;
void explain(TNode literal, std::vector<TNode>& assumptions) override
{
Unreachable("AlgebraicSolver does not propagate.\n");
}
EqualityStatus getEqualityStatus(TNode a, TNode b) override;
bool collectModelInfo(TheoryModel* m, bool fullModel) override;
Node getModelValue(TNode node) override;
bool isComplete() override;
void assertFact(TNode fact) override;
};
} // namespace bv
} // namespace theory
} // namespace CVC4
|
