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/******************************************************************************
* Top contributors (to current version):
* Andrew Reynolds
*
* 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.
* ****************************************************************************
*
* Skolem definition manager.
*/
#include "prop/skolem_def_manager.h"
#include "expr/attribute.h"
namespace cvc5 {
namespace prop {
SkolemDefManager::SkolemDefManager(context::Context* context,
context::UserContext* userContext)
: d_skDefs(userContext), d_skActive(context)
{
}
SkolemDefManager::~SkolemDefManager() {}
void SkolemDefManager::notifySkolemDefinition(TNode skolem, Node def)
{
// Notice that skolem may have kind SKOLEM or BOOLEAN_TERM_VARIABLE
Trace("sk-defs") << "notifySkolemDefinition: " << def << " for " << skolem
<< std::endl;
// in very rare cases, a skolem may be generated twice for terms that are
// equivalent up to purification
if (d_skDefs.find(skolem) == d_skDefs.end())
{
d_skDefs.insert(skolem, def);
}
}
TNode SkolemDefManager::getDefinitionForSkolem(TNode skolem) const
{
NodeNodeMap::const_iterator it = d_skDefs.find(skolem);
Assert(it != d_skDefs.end()) << "No skolem def for " << skolem;
return it->second;
}
void SkolemDefManager::notifyAsserted(TNode literal,
std::vector<TNode>& activatedSkolems,
bool useDefs)
{
std::unordered_set<Node, NodeHashFunction> skolems;
getSkolems(literal, skolems);
for (const Node& k : skolems)
{
if (d_skActive.find(k) != d_skActive.end())
{
// already active
continue;
}
d_skActive.insert(k);
if (useDefs)
{
// add its definition to the activated list
NodeNodeMap::const_iterator it = d_skDefs.find(k);
Assert(it != d_skDefs.end());
activatedSkolems.push_back(it->second);
}
else
{
// add to the activated list
activatedSkolems.push_back(k);
}
}
}
struct HasSkolemTag
{
};
struct HasSkolemComputedTag
{
};
/** Attribute true for nodes with skolems in them */
typedef expr::Attribute<HasSkolemTag, bool> HasSkolemAttr;
/** Attribute true for nodes where we have computed the above attribute */
typedef expr::Attribute<HasSkolemComputedTag, bool> HasSkolemComputedAttr;
bool SkolemDefManager::hasSkolems(TNode n) const
{
std::unordered_set<TNode, TNodeHashFunction> visited;
std::unordered_set<TNode, TNodeHashFunction>::iterator it;
std::vector<TNode> visit;
TNode cur;
visit.push_back(n);
do
{
cur = visit.back();
if (cur.getAttribute(HasSkolemComputedAttr()))
{
visit.pop_back();
// already computed
continue;
}
it = visited.find(cur);
if (it == visited.end())
{
visited.insert(cur);
if (cur.getNumChildren() == 0)
{
visit.pop_back();
bool hasSkolem = false;
if (cur.isVar())
{
hasSkolem = (d_skDefs.find(cur) != d_skDefs.end());
}
cur.setAttribute(HasSkolemAttr(), hasSkolem);
cur.setAttribute(HasSkolemComputedAttr(), true);
}
else
{
visit.insert(visit.end(), cur.begin(), cur.end());
}
}
else
{
visit.pop_back();
bool hasSkolem = false;
for (TNode i : cur)
{
Assert(i.getAttribute(HasSkolemComputedAttr()));
if (i.getAttribute(HasSkolemAttr()))
{
hasSkolem = true;
break;
}
}
cur.setAttribute(HasSkolemAttr(), hasSkolem);
cur.setAttribute(HasSkolemComputedAttr(), true);
}
} while (!visit.empty());
Assert(n.getAttribute(HasSkolemComputedAttr()));
return n.getAttribute(HasSkolemAttr());
}
void SkolemDefManager::getSkolems(
TNode n, std::unordered_set<Node, NodeHashFunction>& skolems) const
{
std::unordered_set<TNode, TNodeHashFunction> visited;
std::unordered_set<TNode, TNodeHashFunction>::iterator it;
std::vector<TNode> visit;
TNode cur;
visit.push_back(n);
do
{
cur = visit.back();
visit.pop_back();
if (!hasSkolems(cur))
{
// does not have skolems, continue
continue;
}
it = visited.find(cur);
if (it == visited.end())
{
visited.insert(cur);
if (cur.isVar())
{
if (d_skDefs.find(cur) != d_skDefs.end())
{
skolems.insert(cur);
}
}
else
{
visit.insert(visit.end(), cur.begin(), cur.end());
}
}
} while (!visit.empty());
}
} // namespace prop
} // namespace cvc5
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