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
|
/********************* */
/*! \file sygus_abduct.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** 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
**
** \brief Implementation of sygus abduction preprocessing pass, which
** transforms an arbitrary input into an abduction problem.
**/
#include "preprocessing/passes/sygus_abduct.h"
#include "expr/node_algorithm.h"
#include "smt/smt_engine.h"
#include "smt/smt_engine_scope.h"
#include "smt/smt_statistics_registry.h"
#include "theory/quantifiers/quantifiers_attributes.h"
#include "theory/quantifiers/quantifiers_rewriter.h"
#include "theory/quantifiers/term_util.h"
#include "theory/rewriter.h"
using namespace std;
using namespace CVC4::kind;
namespace CVC4 {
namespace preprocessing {
namespace passes {
SygusAbduct::SygusAbduct(PreprocessingPassContext* preprocContext)
: PreprocessingPass(preprocContext, "sygus-abduct"){};
PreprocessingPassResult SygusAbduct::applyInternal(
AssertionPipeline* assertionsToPreprocess)
{
NodeManager* nm = NodeManager::currentNM();
Trace("sygus-abduct") << "Run sygus abduct..." << std::endl;
Trace("sygus-abduct-debug") << "Collect symbols..." << std::endl;
std::unordered_set<Node, NodeHashFunction> symset;
std::vector<Node>& asserts = assertionsToPreprocess->ref();
// do we have any assumptions, e.g. via check-sat-assuming?
bool usingAssumptions = (assertionsToPreprocess->getNumAssumptions() > 0);
// The following is our set of "axioms". We construct this set only when the
// usingAssumptions (above) is true. In this case, our input formula is
// partitioned into Fa ^ Fc as described in the header of this class, where:
// - The conjunction of assertions marked as assumptions are the negated
// conjecture Fc, and
// - The conjunction of all other assertions are the axioms Fa.
std::vector<Node> axioms;
for (size_t i = 0, size = asserts.size(); i < size; i++)
{
expr::getSymbols(asserts[i], symset);
// if we are not an assumption, add it to the set of axioms
if (usingAssumptions && i < assertionsToPreprocess->getAssumptionsStart())
{
axioms.push_back(asserts[i]);
}
}
Trace("sygus-abduct-debug")
<< "...finish, got " << symset.size() << " symbols." << std::endl;
Trace("sygus-abduct-debug") << "Setup symbols..." << std::endl;
std::vector<Node> syms;
std::vector<Node> vars;
std::vector<Node> varlist;
std::vector<TypeNode> varlistTypes;
for (const Node& s : symset)
{
TypeNode tn = s.getType();
if (tn.isFirstClass())
{
std::stringstream ss;
ss << s;
Node var = nm->mkBoundVar(tn);
syms.push_back(s);
vars.push_back(var);
Node vlv = nm->mkBoundVar(ss.str(), tn);
varlist.push_back(vlv);
varlistTypes.push_back(tn);
}
}
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make abduction predicate..." << std::endl;
// make the abduction predicate to synthesize
TypeNode abdType = varlistTypes.empty() ? nm->booleanType()
: nm->mkPredicateType(varlistTypes);
Node abd = nm->mkBoundVar("A", abdType);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make abduction predicate app..." << std::endl;
std::vector<Node> achildren;
achildren.push_back(abd);
achildren.insert(achildren.end(), vars.begin(), vars.end());
Node abdApp = vars.empty() ? abd : nm->mkNode(APPLY_UF, achildren);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Set attributes..." << std::endl;
// set the sygus bound variable list
Node abvl = nm->mkNode(BOUND_VAR_LIST, varlist);
abd.setAttribute(theory::SygusSynthFunVarListAttribute(), abvl);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make conjecture body..." << std::endl;
Node input = asserts.size() == 1 ? asserts[0] : nm->mkNode(AND, asserts);
input = input.substitute(syms.begin(), syms.end(), vars.begin(), vars.end());
// A(x) => ~input( x )
input = nm->mkNode(OR, abdApp.negate(), input.negate());
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make conjecture..." << std::endl;
Node res = input.negate();
if (!vars.empty())
{
Node bvl = nm->mkNode(BOUND_VAR_LIST, vars);
// exists x. ~( A( x ) => ~input( x ) )
res = nm->mkNode(EXISTS, bvl, res);
}
// sygus attribute
Node sygusVar = nm->mkSkolem("sygus", nm->booleanType());
theory::SygusAttribute ca;
sygusVar.setAttribute(ca, true);
Node instAttr = nm->mkNode(INST_ATTRIBUTE, sygusVar);
std::vector<Node> iplc;
iplc.push_back(instAttr);
if (!axioms.empty())
{
Node aconj = axioms.size() == 1 ? axioms[0] : nm->mkNode(AND, axioms);
aconj =
aconj.substitute(syms.begin(), syms.end(), vars.begin(), vars.end());
Trace("sygus-abduct") << "---> Assumptions: " << aconj << std::endl;
Node sc = nm->mkNode(AND, aconj, abdApp);
Node vbvl = nm->mkNode(BOUND_VAR_LIST, vars);
sc = nm->mkNode(EXISTS, vbvl, sc);
Node sygusScVar = nm->mkSkolem("sygus_sc", nm->booleanType());
sygusScVar.setAttribute(theory::SygusSideConditionAttribute(), sc);
instAttr = nm->mkNode(INST_ATTRIBUTE, sygusScVar);
// build in the side condition
// exists x. A( x ) ^ input_axioms( x )
// as an additional annotation on the sygus conjecture. In other words,
// the abducts A we procedure must be consistent with our axioms.
iplc.push_back(instAttr);
}
Node instAttrList = nm->mkNode(INST_PATTERN_LIST, iplc);
Node fbvl = nm->mkNode(BOUND_VAR_LIST, abd);
// forall A. exists x. ~( A( x ) => ~input( x ) )
res = nm->mkNode(FORALL, fbvl, res, instAttrList);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
res = theory::Rewriter::rewrite(res);
Trace("sygus-abduct") << "Generate: " << res << std::endl;
Node trueNode = nm->mkConst(true);
assertionsToPreprocess->replace(0, res);
for (size_t i = 1, size = assertionsToPreprocess->size(); i < size; ++i)
{
assertionsToPreprocess->replace(i, trueNode);
}
return PreprocessingPassResult::NO_CONFLICT;
}
} // namespace passes
} // namespace preprocessing
} // namespace CVC4
|
