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/******************************************************************************
* Top contributors (to current version):
* Andrew Reynolds, Aina Niemetz
*
* This file is part of the cvc5 project.
*
* Copyright (c) 2009-2021 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.
* ****************************************************************************
*
* Implementation of sygus abduction utility, which transforms an arbitrary
* input into an abduction problem.
*/
#include "theory/quantifiers/sygus/sygus_abduct.h"
#include <sstream>
#include "expr/dtype.h"
#include "expr/node_algorithm.h"
#include "expr/skolem_manager.h"
#include "expr/sygus_datatype.h"
#include "theory/datatypes/sygus_datatype_utils.h"
#include "theory/quantifiers/quantifiers_attributes.h"
#include "theory/quantifiers/quantifiers_rewriter.h"
#include "theory/quantifiers/sygus/sygus_grammar_cons.h"
#include "theory/quantifiers/sygus/sygus_utils.h"
#include "theory/quantifiers/term_util.h"
#include "theory/rewriter.h"
using namespace std;
using namespace cvc5::kind;
namespace cvc5 {
namespace theory {
namespace quantifiers {
SygusAbduct::SygusAbduct() {}
Node SygusAbduct::mkAbductionConjecture(const std::string& name,
const std::vector<Node>& asserts,
const std::vector<Node>& axioms,
TypeNode abdGType)
{
NodeManager* nm = NodeManager::currentNM();
SkolemManager* sm = nm->getSkolemManager();
std::unordered_set<Node, NodeHashFunction> symset;
for (size_t i = 0, size = asserts.size(); i < size; i++)
{
expr::getSymbols(asserts[i], symset);
}
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.isConstructor() || tn.isSelector() || tn.isTester())
{
// datatype symbols should be considered interpreted symbols here, not
// (higher-order) variables.
continue;
}
// Notice that we allow for non-first class (e.g. function) variables here.
// This is applicable to the case where we are doing get-abduct in a logic
// with UF.
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);
// set that this variable encodes the term s
SygusVarToTermAttribute sta;
vlv.setAttribute(sta, s);
}
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(name.c_str(), abdType);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
// the sygus variable list
Node abvl;
// if provided, we will associate the provide sygus datatype type with the
// function-to-synthesize. However, we must convert it so that its
// free symbols are universally quantified.
if (!abdGType.isNull())
{
Assert(abdGType.isDatatype() && abdGType.getDType().isSygus());
Trace("sygus-abduct-debug") << "Process abduction type:" << std::endl;
Trace("sygus-abduct-debug") << abdGType.getDType().getName() << std::endl;
// substitute the free symbols of the grammar with variables corresponding
// to the formal argument list of the new sygus datatype type.
TypeNode abdGTypeS = datatypes::utils::substituteAndGeneralizeSygusType(
abdGType, syms, varlist);
Assert(abdGTypeS.isDatatype() && abdGTypeS.getDType().isSygus());
Trace("sygus-abduct-debug")
<< "Make sygus grammar attribute..." << std::endl;
Node sym = nm->mkBoundVar("sfproxy_abduct", abdGTypeS);
// Set the sygus grammar attribute to indicate that abdGTypeS encodes the
// grammar for abd.
theory::SygusSynthGrammarAttribute ssg;
abd.setAttribute(ssg, sym);
Trace("sygus-abduct-debug") << "Finished setting up grammar." << std::endl;
// use the bound variable list from the new substituted grammar type
const DType& agtsd = abdGTypeS.getDType();
abvl = agtsd.getSygusVarList();
Assert(!abvl.isNull() && abvl.getKind() == BOUND_VAR_LIST);
}
else if (!varlist.empty())
{
// the bound variable list of the abduct-to-synthesize is determined by
// the variable list above
abvl = nm->mkNode(BOUND_VAR_LIST, varlist);
// We do not set a grammar type for abd (SygusSynthGrammarAttribute).
// Its grammar will be constructed internally in the default way
}
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
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 aconj = axioms.size() == 0
? nm->mkConst(true)
: (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);
if (!vars.empty())
{
Node vbvl = nm->mkNode(BOUND_VAR_LIST, vars);
sc = nm->mkNode(EXISTS, vbvl, sc);
}
Node sygusScVar = sm->mkDummySkolem("sygus_sc", nm->booleanType());
sygusScVar.setAttribute(theory::SygusSideConditionAttribute(), sc);
Node 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.
// forall A. exists x. ~( A( x ) => ~input( x ) )
res = SygusUtils::mkSygusConjecture({abd}, res, {instAttr});
Trace("sygus-abduct-debug") << "...finish" << std::endl;
res = theory::Rewriter::rewrite(res);
Trace("sygus-abduct") << "Generate: " << res << std::endl;
return res;
}
} // namespace quantifiers
} // namespace theory
} // namespace cvc5
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