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/********************* */
/*! \file sygus_inference.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2017 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_inference
**/
#include "theory/quantifiers/sygus_inference.h"
#include "theory/quantifiers/quantifiers_attributes.h"
#include "theory/quantifiers/quantifiers_rewriter.h"
using namespace CVC4::kind;
namespace CVC4 {
namespace theory {
namespace quantifiers {
SygusInference::SygusInference() {}
bool SygusInference::simplify(std::vector<Node>& assertions)
{
Trace("sygus-infer") << "Run sygus inference..." << std::endl;
if (assertions.empty())
{
Trace("sygus-infer") << "...fail: empty assertions." << std::endl;
return false;
}
NodeManager* nm = NodeManager::currentNM();
// collect free variables in all assertions
std::vector<Node> qvars;
std::map<TypeNode, std::vector<Node> > qtvars;
std::vector<Node> free_functions;
std::vector<TNode> visit;
std::unordered_set<TNode, TNodeHashFunction> visited;
// add top-level conjuncts to eassertions
std::vector<Node> assertions_proc = assertions;
std::vector<Node> eassertions;
unsigned index = 0;
while (index < assertions_proc.size())
{
Node ca = assertions_proc[index];
if (ca.getKind() == AND)
{
for (const Node& ai : ca)
{
assertions_proc.push_back(ai);
}
}
else
{
eassertions.push_back(ca);
}
index++;
}
// process eassertions
std::vector<Node> processed_assertions;
for (const Node& as : eassertions)
{
// substitution for this assertion
std::vector<Node> vars;
std::vector<Node> subs;
std::map<TypeNode, unsigned> type_count;
Node pas = as;
// rewrite
pas = Rewriter::rewrite(pas);
Trace("sygus-infer") << "assertion : " << pas << std::endl;
if (pas.getKind() == FORALL)
{
// preprocess the quantified formula
pas = quantifiers::QuantifiersRewriter::preprocess(pas);
Trace("sygus-infer-debug") << " ...preprocessed to " << pas << std::endl;
}
if (pas.getKind() == FORALL)
{
// infer prefix
for (const Node& v : pas[0])
{
TypeNode tnv = v.getType();
unsigned vnum = type_count[tnv];
type_count[tnv]++;
if (vnum < qtvars[tnv].size())
{
vars.push_back(v);
subs.push_back(qtvars[tnv][vnum]);
}
else
{
Assert(vnum == qtvars[tnv].size());
qtvars[tnv].push_back(v);
qvars.push_back(v);
}
}
pas = pas[1];
if (!vars.empty())
{
pas =
pas.substitute(vars.begin(), vars.end(), subs.begin(), subs.end());
}
}
Trace("sygus-infer-debug") << " ...substituted to " << pas << std::endl;
// collect free functions, ensure no quantified formulas
TNode cur = pas;
// compute free variables
visit.push_back(cur);
do
{
cur = visit.back();
visit.pop_back();
if (visited.find(cur) == visited.end())
{
visited.insert(cur);
if (cur.getKind() == APPLY_UF)
{
Node op = cur.getOperator();
if (std::find(free_functions.begin(), free_functions.end(), op)
== free_functions.end())
{
free_functions.push_back(op);
}
}
else if (cur.getKind() == FORALL)
{
Trace("sygus-infer")
<< "...fail: non-top-level quantifier." << std::endl;
return false;
}
for (const TNode& cn : cur)
{
visit.push_back(cn);
}
}
} while (!visit.empty());
processed_assertions.push_back(pas);
}
// if no free function symbols, there is no use changing into SyGuS
if (free_functions.empty())
{
Trace("sygus-infer") << "...fail: no free function symbols." << std::endl;
return false;
}
Assert(!processed_assertions.empty());
// conjunction of the assertions
Trace("sygus-infer") << "Construct body..." << std::endl;
Node body;
if (processed_assertions.size() == 1)
{
body = processed_assertions[0];
}
else
{
body = nm->mkNode(AND, processed_assertions);
}
// for each free function symbol, make a bound variable of the same type
Trace("sygus-infer") << "Do free function substitution..." << std::endl;
std::vector<Node> ff_vars;
for (const Node& ff : free_functions)
{
Node ffv = nm->mkBoundVar(ff.getType());
ff_vars.push_back(ffv);
}
// substitute free functions -> variables
body = body.substitute(free_functions.begin(),
free_functions.end(),
ff_vars.begin(),
ff_vars.end());
Trace("sygus-infer-debug") << "...got : " << body << std::endl;
// quantify the body
Trace("sygus-infer") << "Make inner sygus conjecture..." << std::endl;
if (!qvars.empty())
{
Node bvl = nm->mkNode(BOUND_VAR_LIST, qvars);
body = nm->mkNode(EXISTS, bvl, body.negate());
}
// sygus attribute to mark the conjecture as a sygus conjecture
Trace("sygus-infer") << "Make outer sygus conjecture..." << std::endl;
Node sygusVar = nm->mkBoundVar("sygus", nm->booleanType());
SygusAttribute ca;
sygusVar.setAttribute(ca, true);
Node instAttr = nm->mkNode(INST_ATTRIBUTE, sygusVar);
Node instAttrList = nm->mkNode(INST_PATTERN_LIST, instAttr);
Node fbvl = nm->mkNode(BOUND_VAR_LIST, ff_vars);
body = nm->mkNode(FORALL, fbvl, body, instAttrList);
Trace("sygus-infer") << "*** Return sygus inference : " << body << std::endl;
// replace all assertions except the first with true
Node truen = nm->mkConst(true);
for (unsigned i = 0, size = assertions.size(); i < size; i++)
{
if (i == 0)
{
assertions[i] = body;
}
else
{
assertions[i] = truen;
}
}
return true;
}
} /* CVC4::theory::quantifiers namespace */
} /* CVC4::theory namespace */
} /* CVC4 namespace */
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