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/********************* */
/*! \file union_find.h
** \verbatim
** Top contributors (to current version):
** Morgan Deters, Mathias Preiner, Tim King
** 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 Path-compressing, backtrackable union-find using an undo
** stack. Refactored from the UF union-find.
**
** Path-compressing, backtrackable union-find using an undo stack
** rather than storing items in a CDMap<>.
**/
#include "cvc4_private.h"
#ifndef CVC4__THEORY__ARRAYS__UNION_FIND_H
#define CVC4__THEORY__ARRAYS__UNION_FIND_H
#include <utility>
#include <vector>
#include <unordered_map>
#include "expr/node.h"
#include "context/cdo.h"
namespace CVC4 {
namespace context {
class Context;
}/* CVC4::context namespace */
namespace theory {
namespace arrays {
// NodeType \in { Node, TNode }
template <class NodeType, class NodeHash>
class UnionFind : context::ContextNotifyObj {
/** Our underlying map type. */
typedef std::unordered_map<NodeType, NodeType, NodeHash> MapType;
/**
* Our map of Nodes to their canonical representatives.
* If a Node is not present in the map, it is its own
* representative.
*/
MapType d_map;
/** Our undo stack for changes made to d_map. */
std::vector<std::pair<TNode, TNode> > d_trace;
/** Our current offset in the d_trace stack (context-dependent). */
context::CDO<size_t> d_offset;
public:
UnionFind(context::Context* ctxt) :
context::ContextNotifyObj(ctxt),
d_offset(ctxt, 0) {
}
/**
* Return a Node's union-find representative, doing path compression.
*/
inline TNode find(TNode n);
/**
* Return a Node's union-find representative, NOT doing path compression.
* This is useful for Assert() statements, debug checking, and similar
* things that you do NOT want to mutate the structure.
*/
inline TNode debugFind(TNode n) const;
/**
* Set the canonical representative of n to newParent. They should BOTH
* be their own canonical representatives on entry to this funciton.
*/
inline void setCanon(TNode n, TNode newParent);
/**
* Called by the Context when a pop occurs. Cancels everything to the
* current context level. Overrides ContextNotifyObj::notify().
*/
void notify();
};/* class UnionFind<> */
template <class NodeType, class NodeHash>
inline TNode UnionFind<NodeType, NodeHash>::debugFind(TNode n) const {
typename MapType::const_iterator i = d_map.find(n);
if(i == d_map.end()) {
return n;
} else {
return debugFind((*i).second);
}
}
template <class NodeType, class NodeHash>
inline TNode UnionFind<NodeType, NodeHash>::find(TNode n) {
Trace("arraysuf") << "arraysUF find of " << n << std::endl;
typename MapType::iterator i = d_map.find(n);
if(i == d_map.end()) {
Trace("arraysuf") << "arraysUF it is rep" << std::endl;
return n;
} else {
Trace("arraysuf") << "arraysUF not rep: par is " << (*i).second << std::endl;
std::pair<TNode, TNode> pr = *i;
// our iterator is invalidated by the recursive call to find(),
// since it mutates the map
TNode p = find(pr.second);
if(p == pr.second) {
return p;
}
d_trace.push_back(std::make_pair(n, pr.second));
d_offset = d_trace.size();
Trace("arraysuf") << "arraysUF setting canon of " << n << " : " << p << " @ " << d_trace.size() << std::endl;
pr.second = p;
d_map.insert(pr);
return p;
}
}
template <class NodeType, class NodeHash>
inline void UnionFind<NodeType, NodeHash>::setCanon(TNode n, TNode newParent) {
Assert(d_map.find(n) == d_map.end());
Assert(d_map.find(newParent) == d_map.end());
if(n != newParent) {
Trace("arraysuf") << "arraysUF setting canon of " << n << " : " << newParent << " @ " << d_trace.size() << std::endl;
d_map[n] = newParent;
d_trace.push_back(std::make_pair(n, TNode::null()));
d_offset = d_trace.size();
}
}
}/* CVC4::theory::arrays namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
#endif /*CVC4__THEORY__ARRAYS__UNION_FIND_H */
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