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
|
/********************* */
/*! \file sygus_abduct.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2020 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 Sygus abduction utility, which transforms an arbitrary input into an
** abduction problem.
**/
#ifndef CVC4__THEORY__QUANTIFIERS__SYGUS_ABDUCT_H
#define CVC4__THEORY__QUANTIFIERS__SYGUS_ABDUCT_H
#include <string>
#include <vector>
#include "expr/node.h"
#include "expr/type.h"
namespace CVC4 {
namespace theory {
namespace quantifiers {
/** SygusAbduct
*
* A utility that turns a set of quantifier-free assertions into
* a sygus conjecture that encodes an abduction problem. In detail, if our
* input formula is F( x ) for free symbols x, then we construct the sygus
* conjecture:
*
* exists A. forall x. ( A( x ) => ~F( x ) )
*
* where A( x ) is a predicate over the free symbols of our input. In other
* words, A( x ) is a sufficient condition for showing ~F( x ).
*
* Another way to view this is A( x ) is any condition such that A( x ) ^ F( x )
* is unsatisfiable.
*
* A common use case is to find the weakest such A that meets the above
* specification. We do this by streaming solutions (sygus-stream) for A
* while filtering stronger solutions (sygus-filter-sol=strong). These options
* are enabled by default when this preprocessing class is used (sygus-abduct).
*
* If the input F( x ) is partitioned into axioms Fa and negated conjecture Fc
* Fa( x ) ^ Fc( x ), then the sygus conjecture we construct is:
*
* exists A. ( exists y. A( y ) ^ Fa( y ) ) ^ forall x. ( A( x ) => ~F( x ) )
*
* In other words, A( y ) must be consistent with our axioms Fa and imply
* ~F( x ). We encode this conjecture using SygusSideConditionAttribute.
*/
class SygusAbduct
{
public:
SygusAbduct();
/**
* Returns the sygus conjecture corresponding to the abduction problem for
* input problem (F above) given by asserts, and axioms (Fa above) given by
* axioms. Note that axioms is expected to be a subset of asserts.
*
* The argument name is the name for the abduct-to-synthesize.
*
* The type abdGType (if non-null) is a sygus datatype type that encodes the
* grammar that should be used for solutions of the abduction conjecture.
*
* The relationship between the free variables of asserts and the formal
* rgument list of the abduct-to-synthesize are tracked by the attribute
* SygusVarToTermAttribute.
*
* In particular, solutions to the synthesis conjecture will be in the form
* of a closed term (lambda varlist. t). The intended solution, which is a
* term whose free variables are a subset of asserts, is the term
* t * { varlist -> SygusVarToTermAttribute(varlist) }.
*/
static Node mkAbductionConjecture(const std::string& name,
const std::vector<Node>& asserts,
const std::vector<Node>& axioms,
TypeNode abdGType);
};
} // namespace quantifiers
} // namespace theory
} // namespace CVC4
#endif /* CVC4__THEORY__QUANTIFIERS__SYGUS_ABDUCT_H */
|
