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/********************* */
/*! \file let_binding.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 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.\endverbatim
**
** \brief A let binding utility
**/
#include "printer/let_binding.h"
#include <sstream>
namespace CVC5 {
LetBinding::LetBinding(uint32_t thresh)
: d_thresh(thresh),
d_context(),
d_visitList(&d_context),
d_count(&d_context),
d_letList(&d_context),
d_letMap(&d_context)
{
}
uint32_t LetBinding::getThreshold() const { return d_thresh; }
void LetBinding::process(Node n)
{
if (n.isNull() || d_thresh == 0)
{
// value of 0 means do not introduce let
return;
}
// update the count of occurrences
updateCounts(n);
}
void LetBinding::letify(Node n, std::vector<Node>& letList)
{
// first, push the context
pushScope();
// process the node
process(n);
// now, letify
letify(letList);
}
void LetBinding::letify(std::vector<Node>& letList)
{
size_t prevSize = d_letList.size();
// populate the d_letList and d_letMap
convertCountToLet();
// add the new entries to the letList
letList.insert(letList.end(), d_letList.begin() + prevSize, d_letList.end());
}
void LetBinding::pushScope() { d_context.push(); }
void LetBinding::popScope() { d_context.pop(); }
uint32_t LetBinding::getId(Node n) const
{
NodeIdMap::const_iterator it = d_letMap.find(n);
if (it == d_letMap.end())
{
return 0;
}
return (*it).second;
}
Node LetBinding::convert(Node n, const std::string& prefix, bool letTop) const
{
if (d_letMap.empty())
{
return n;
}
NodeManager* nm = NodeManager::currentNM();
std::unordered_map<TNode, Node, TNodeHashFunction> visited;
std::unordered_map<TNode, Node, TNodeHashFunction>::iterator it;
std::vector<TNode> visit;
TNode cur;
visit.push_back(n);
do
{
cur = visit.back();
visit.pop_back();
it = visited.find(cur);
if (it == visited.end())
{
uint32_t id = getId(cur);
// do not letify id 0, or n itself if letTop is false
if (id > 0 && (cur != n || letTop))
{
// make the let variable
std::stringstream ss;
ss << prefix << id;
visited[cur] = nm->mkBoundVar(ss.str(), cur.getType());
}
else if (cur.isClosure())
{
// do not convert beneath quantifiers
visited[cur] = cur;
}
else
{
visited[cur] = Node::null();
visit.push_back(cur);
visit.insert(visit.end(), cur.begin(), cur.end());
}
}
else if (it->second.isNull())
{
Node ret = cur;
bool childChanged = false;
std::vector<Node> children;
if (cur.getMetaKind() == kind::metakind::PARAMETERIZED)
{
children.push_back(cur.getOperator());
}
for (const Node& cn : cur)
{
it = visited.find(cn);
Assert(it != visited.end());
Assert(!it->second.isNull());
childChanged = childChanged || cn != it->second;
children.push_back(it->second);
}
if (childChanged)
{
ret = nm->mkNode(cur.getKind(), children);
}
visited[cur] = ret;
}
} while (!visit.empty());
Assert(visited.find(n) != visited.end());
Assert(!visited.find(n)->second.isNull());
return visited[n];
}
void LetBinding::updateCounts(Node n)
{
NodeIdMap::iterator it;
std::vector<Node> visit;
TNode cur;
visit.push_back(n);
do
{
cur = visit.back();
it = d_count.find(cur);
if (it == d_count.end())
{
// do not traverse beneath quantifiers
if (cur.getNumChildren() == 0 || cur.isClosure())
{
d_visitList.push_back(cur);
d_count[cur] = 1;
visit.pop_back();
}
else
{
d_count[cur] = 0;
visit.insert(visit.end(), cur.begin(), cur.end());
}
}
else
{
if ((*it).second == 0)
{
d_visitList.push_back(cur);
}
d_count[cur] = (*it).second + 1;
visit.pop_back();
}
} while (!visit.empty());
}
void LetBinding::convertCountToLet()
{
Assert(d_thresh > 0);
// Assign ids for those whose d_count is >= d_thresh, traverse in d_visitList
// in order so that deeper nodes are assigned lower identifiers, which
// ensures the let list can be printed.
NodeIdMap::const_iterator itc;
for (const Node& n : d_visitList)
{
if (n.getNumChildren() == 0)
{
// do not letify terms with no children
continue;
}
else if (d_letMap.find(n) != d_letMap.end())
{
// already letified, perhaps at a lower context
continue;
}
itc = d_count.find(n);
Assert(itc != d_count.end());
if ((*itc).second >= d_thresh)
{
d_letList.push_back(n);
// start with id 1
size_t id = d_letMap.size() + 1;
d_letMap[n] = id;
}
}
}
} // namespace CVC5
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