Head

GCC Code Coverage Report

Directory:	.		Exec	Total	Coverage
File:	src/expr/skolem_manager.cpp	Lines:	154	157	98.1 %
Date:	2021-05-21	Branches:	308	745	41.3 %


/******************************************************************************
 * 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 skolem manager class.
 */

#include "expr/skolem_manager.h"

#include <sstream>

#include "expr/attribute.h"
#include "expr/bound_var_manager.h"
#include "expr/node_algorithm.h"

using namespace cvc5::kind;

namespace cvc5 {

// Attributes are global maps from Nodes to data. Thus, note that these could
// be implemented as internal maps in SkolemManager.
struct WitnessFormAttributeId
{
};
typedef expr::Attribute<WitnessFormAttributeId, Node> WitnessFormAttribute;

struct SkolemFormAttributeId
{
};
typedef expr::Attribute<SkolemFormAttributeId, Node> SkolemFormAttribute;

struct OriginalFormAttributeId
{
};
typedef expr::Attribute<OriginalFormAttributeId, Node> OriginalFormAttribute;

const char* toString(SkolemFunId id)
{
  switch (id)
  {
    case SkolemFunId::DIV_BY_ZERO: return "DIV_BY_ZERO";
    case SkolemFunId::INT_DIV_BY_ZERO: return "INT_DIV_BY_ZERO";
    case SkolemFunId::MOD_BY_ZERO: return "MOD_BY_ZERO";
    case SkolemFunId::SQRT: return "SQRT";
    case SkolemFunId::SELECTOR_WRONG: return "SELECTOR_WRONG";
    case SkolemFunId::SEQ_NTH_OOB: return "SEQ_NTH_OOB";
    default: return "?";
  }
}

std::ostream& operator<<(std::ostream& out, SkolemFunId id)
{
  out << toString(id);
  return out;
}

Node SkolemManager::mkSkolem(Node v,
                             Node pred,
                             const std::string& prefix,
                             const std::string& comment,
                             int flags,
                             ProofGenerator* pg)
{
  // We do not currently insist that pred does not contain witness terms
  Assert(v.getKind() == BOUND_VARIABLE);
  // make the witness term
  NodeManager* nm = NodeManager::currentNM();
  Node bvl = nm->mkNode(BOUND_VAR_LIST, v);
  // Make the witness term, where notice that pred may contain skolems. We do
  // not recursively convert pred to witness form, since witness terms should
  // be treated as opaque. Moreover, the use of witness forms leads to
  // variable shadowing issues in e.g. skolemization.
  Node w = nm->mkNode(WITNESS, bvl, pred);
  // store the mapping to proof generator if it exists
  if (pg != nullptr)
  {
    // We cache based on the existential of the original predicate
    Node q = nm->mkNode(EXISTS, bvl, pred);
    // Notice this may overwrite an existing proof generator. This does not
    // matter since either should be able to prove q.
    d_gens[q] = pg;
  }
  Node k = mkSkolemInternal(w, prefix, comment, flags);
  // set witness form attribute for k
  WitnessFormAttribute wfa;
  k.setAttribute(wfa, w);
  Trace("sk-manager-skolem")
      << "skolem: " << k << " witness " << w << std::endl;
  return k;
}

Node SkolemManager::mkSkolemize(Node q,
                                std::vector<Node>& skolems,
                                const std::string& prefix,
                                const std::string& comment,
                                int flags,
                                ProofGenerator* pg)
{
  Trace("sk-manager-debug") << "mkSkolemize " << q << std::endl;
  Assert(q.getKind() == EXISTS);
  Node currQ = q;
  for (const Node& av : q[0])
  {
    Assert(currQ.getKind() == EXISTS && av == currQ[0][0]);
    // currQ is updated to the result of skolemizing its first variable in
    // the method below.
    Node sk = skolemize(currQ, currQ, prefix, comment, flags);
    Trace("sk-manager-debug")
        << "made skolem " << sk << " for " << av << std::endl;
    skolems.push_back(sk);
  }
  if (pg != nullptr)
  {
    // Same as above, this may overwrite an existing proof generator
    d_gens[q] = pg;
  }
  Trace("sk-manager-debug") << "...mkSkolemize returns " << currQ << std::endl;
  return currQ;
}

Node SkolemManager::skolemize(Node q,
                              Node& qskolem,
                              const std::string& prefix,
                              const std::string& comment,
                              int flags)
{
  Assert(q.getKind() == EXISTS);
  Node v;
  std::vector<Node> ovars;
  Trace("sk-manager-debug") << "mkSkolemize..." << std::endl;
  NodeManager* nm = NodeManager::currentNM();
  for (const Node& av : q[0])
  {
    if (v.isNull())
    {
      v = av;
      continue;
    }
    ovars.push_back(av);
  }
  Assert(!v.isNull());
  // make the predicate with one variable stripped off
  Node pred = q[1];
  Trace("sk-manager-debug") << "make exists predicate" << std::endl;
  if (!ovars.empty())
  {
    // keeps the same variables
    Node bvl = nm->mkNode(BOUND_VAR_LIST, ovars);
    // update the predicate
    pred = nm->mkNode(EXISTS, bvl, pred);
  }
  Trace("sk-manager-debug") << "call sub mkSkolem" << std::endl;
  // don't use a proof generator, since this may be an intermediate, partially
  // skolemized formula.
  Node k = mkSkolem(v, pred, prefix, comment, flags, nullptr);
  Assert(k.getType() == v.getType());
  TNode tv = v;
  TNode tk = k;
  Trace("sk-manager-debug")
      << "qskolem apply " << tv << " -> " << tk << " to " << pred << std::endl;
  // the quantified formula with one step of skolemization
  qskolem = pred.substitute(tv, tk);
  Trace("sk-manager-debug") << "qskolem done substitution" << std::endl;
  return k;
}

Node SkolemManager::mkPurifySkolem(Node t,
                                   const std::string& prefix,
                                   const std::string& comment,
                                   int flags)
{
  Node to = getOriginalForm(t);
  // We do not currently insist that to does not contain witness terms

  Node k = mkSkolemInternal(to, prefix, comment, flags);
  // set original form attribute for k
  OriginalFormAttribute ofa;
  k.setAttribute(ofa, to);

  Trace("sk-manager-skolem")
      << "skolem: " << k << " purify " << to << std::endl;
  return k;
}

Node SkolemManager::mkSkolemFunction(SkolemFunId id, TypeNode tn, Node cacheVal)
{
  std::tuple<SkolemFunId, TypeNode, Node> key(id, tn, cacheVal);
  std::map<std::tuple<SkolemFunId, TypeNode, Node>, Node>::iterator it =
      d_skolemFuns.find(key);
  if (it == d_skolemFuns.end())
  {
    NodeManager* nm = NodeManager::currentNM();
    std::stringstream ss;
    ss << "SKOLEM_FUN_" << id;
    Node k = nm->mkSkolem(ss.str(), tn, "an internal skolem function");
    d_skolemFuns[key] = k;
    return k;
  }
  return it->second;
}

Node SkolemManager::mkDummySkolem(const std::string& prefix,
                                  const TypeNode& type,
                                  const std::string& comment,
                                  int flags)
{
  return NodeManager::currentNM()->mkSkolem(prefix, type, comment, flags);
}

ProofGenerator* SkolemManager::getProofGenerator(Node t) const
{
  std::map<Node, ProofGenerator*>::const_iterator it = d_gens.find(t);
  if (it != d_gens.end())
  {
    return it->second;
  }
  return nullptr;
}

Node SkolemManager::getWitnessForm(Node k)
{
  Assert(k.getKind() == SKOLEM);
  // simply look up the witness form for k via an attribute
  WitnessFormAttribute wfa;
  return k.getAttribute(wfa);
}

Node SkolemManager::getOriginalForm(Node n)
{
  if (n.isNull())
  {
    return n;
  }
  Trace("sk-manager-debug")
      << "SkolemManager::getOriginalForm " << n << std::endl;
  OriginalFormAttribute ofa;
  NodeManager* nm = NodeManager::currentNM();
  std::unordered_map<TNode, Node> visited;
  std::unordered_map<TNode, Node>::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())
    {
      if (cur.hasAttribute(ofa))
      {
        visited[cur] = cur.getAttribute(ofa);
      }
      else
      {
        visited[cur] = Node::null();
        visit.push_back(cur);
        if (cur.getMetaKind() == metakind::PARAMETERIZED)
        {
          visit.push_back(cur.getOperator());
        }
        for (const Node& cn : cur)
        {
          visit.push_back(cn);
        }
      }
    }
    else if (it->second.isNull())
    {
      Node ret = cur;
      bool childChanged = false;
      std::vector<Node> children;
      if (cur.getMetaKind() == metakind::PARAMETERIZED)
      {
        it = visited.find(cur.getOperator());
        Assert(it != visited.end());
        Assert(!it->second.isNull());
        childChanged = childChanged || cur.getOperator() != it->second;
        children.push_back(it->second);
      }
      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);
      }
      cur.setAttribute(ofa, ret);
      visited[cur] = ret;
    }
  } while (!visit.empty());
  Assert(visited.find(n) != visited.end());
  Assert(!visited.find(n)->second.isNull());
  Trace("sk-manager-debug") << "..return " << visited[n] << std::endl;
  return visited[n];
}

Node SkolemManager::mkSkolemInternal(Node w,
                                     const std::string& prefix,
                                     const std::string& comment,
                                     int flags)
{
  // note that witness, original forms are independent, but share skolems
  NodeManager* nm = NodeManager::currentNM();
  // w is not necessarily a witness term
  SkolemFormAttribute sfa;
  Node k;
  // could already have a skolem if we used w already
  if (w.hasAttribute(sfa))
  {
    return w.getAttribute(sfa);
  }
  // make the new skolem
  if (flags & NodeManager::SKOLEM_BOOL_TERM_VAR)
  {
    Assert (w.getType().isBoolean());
    k = nm->mkBooleanTermVariable();
  }
  else
  {
    k = nm->mkSkolem(prefix, w.getType(), comment, flags);
  }
  // set skolem form attribute for w
  w.setAttribute(sfa, k);
  Trace("sk-manager") << "SkolemManager::mkSkolem: " << k << " : " << w
                      << std::endl;
  return k;
}

}  // namespace cvc5


Generated by: GCOVR (Version 3.2)

Line	Exec	Source
1		/******************************************************************************
2		* Top contributors (to current version):
3		* Andrew Reynolds, Aina Niemetz
4		*
5		* This file is part of the cvc5 project.
6		*
7		* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
8		* in the top-level source directory and their institutional affiliations.
9		* All rights reserved. See the file COPYING in the top-level source
10		* directory for licensing information.
11		* ****************************************************************************
12		*
13		* Implementation of skolem manager class.
14		*/
15
16		#include "expr/skolem_manager.h"
17
18		#include <sstream>
19
20		#include "expr/attribute.h"
21		#include "expr/bound_var_manager.h"
22		#include "expr/node_algorithm.h"
23
24		using namespace cvc5::kind;
25
26		namespace cvc5 {
27
28		// Attributes are global maps from Nodes to data. Thus, note that these could
29		// be implemented as internal maps in SkolemManager.
30		struct WitnessFormAttributeId
31		{
32		};
33		typedef expr::Attribute<WitnessFormAttributeId, Node> WitnessFormAttribute;
34
35		struct SkolemFormAttributeId
36		{
37		};
38		typedef expr::Attribute<SkolemFormAttributeId, Node> SkolemFormAttribute;
39
40		struct OriginalFormAttributeId
41		{
42		};
43		typedef expr::Attribute<OriginalFormAttributeId, Node> OriginalFormAttribute;
44
45	748	const char* toString(SkolemFunId id)
46		{
47	748	switch (id)
48		{
49	81	case SkolemFunId::DIV_BY_ZERO: return "DIV_BY_ZERO";
50	59	case SkolemFunId::INT_DIV_BY_ZERO: return "INT_DIV_BY_ZERO";
51	32	case SkolemFunId::MOD_BY_ZERO: return "MOD_BY_ZERO";
52	11	case SkolemFunId::SQRT: return "SQRT";
53	547	case SkolemFunId::SELECTOR_WRONG: return "SELECTOR_WRONG";
54	18	case SkolemFunId::SEQ_NTH_OOB: return "SEQ_NTH_OOB";
55		default: return "?";
56		}
57		}
58
59	748	std::ostream& operator<<(std::ostream& out, SkolemFunId id)
60		{
61	748	out << toString(id);
62	748	return out;
63		}
64
65	4866	Node SkolemManager::mkSkolem(Node v,
66		Node pred,
67		const std::string& prefix,
68		const std::string& comment,
69		int flags,
70		ProofGenerator* pg)
71		{
72		// We do not currently insist that pred does not contain witness terms
73	4866	Assert(v.getKind() == BOUND_VARIABLE);
74		// make the witness term
75	4866	NodeManager* nm = NodeManager::currentNM();
76	9732	Node bvl = nm->mkNode(BOUND_VAR_LIST, v);
77		// Make the witness term, where notice that pred may contain skolems. We do
78		// not recursively convert pred to witness form, since witness terms should
79		// be treated as opaque. Moreover, the use of witness forms leads to
80		// variable shadowing issues in e.g. skolemization.
81	9732	Node w = nm->mkNode(WITNESS, bvl, pred);
82		// store the mapping to proof generator if it exists
83	4866	if (pg != nullptr)
84		{
85		// We cache based on the existential of the original predicate
86	2994	Node q = nm->mkNode(EXISTS, bvl, pred);
87		// Notice this may overwrite an existing proof generator. This does not
88		// matter since either should be able to prove q.
89	1497	d_gens[q] = pg;
90		}
91	4866	Node k = mkSkolemInternal(w, prefix, comment, flags);
92		// set witness form attribute for k
93		WitnessFormAttribute wfa;
94	4866	k.setAttribute(wfa, w);
95	9732	Trace("sk-manager-skolem")
96	4866	<< "skolem: " << k << " witness " << w << std::endl;
97	9732	return k;
98		}
99
100	1173	Node SkolemManager::mkSkolemize(Node q,
101		std::vector<Node>& skolems,
102		const std::string& prefix,
103		const std::string& comment,
104		int flags,
105		ProofGenerator* pg)
106		{
107	1173	Trace("sk-manager-debug") << "mkSkolemize " << q << std::endl;
108	1173	Assert(q.getKind() == EXISTS);
109	1173	Node currQ = q;
110	3451	for (const Node& av : q[0])
111		{
112	2278	Assert(currQ.getKind() == EXISTS && av == currQ[0][0]);
113		// currQ is updated to the result of skolemizing its first variable in
114		// the method below.
115	4556	Node sk = skolemize(currQ, currQ, prefix, comment, flags);
116	4556	Trace("sk-manager-debug")
117	2278	<< "made skolem " << sk << " for " << av << std::endl;
118	2278	skolems.push_back(sk);
119		}
120	1173	if (pg != nullptr)
121		{
122		// Same as above, this may overwrite an existing proof generator
123		d_gens[q] = pg;
124		}
125	1173	Trace("sk-manager-debug") << "...mkSkolemize returns " << currQ << std::endl;
126	1173	return currQ;
127		}
128
129	2278	Node SkolemManager::skolemize(Node q,
130		Node& qskolem,
131		const std::string& prefix,
132		const std::string& comment,
133		int flags)
134		{
135	2278	Assert(q.getKind() == EXISTS);
136	4556	Node v;
137	4556	std::vector<Node> ovars;
138	2278	Trace("sk-manager-debug") << "mkSkolemize..." << std::endl;
139	2278	NodeManager* nm = NodeManager::currentNM();
140	7312	for (const Node& av : q[0])
141		{
142	9590	if (v.isNull())
143		{
144	2278	v = av;
145	2278	continue;
146		}
147	5034	ovars.push_back(av);
148		}
149	2278	Assert(!v.isNull());
150		// make the predicate with one variable stripped off
151	4556	Node pred = q[1];
152	2278	Trace("sk-manager-debug") << "make exists predicate" << std::endl;
153	2278	if (!ovars.empty())
154		{
155		// keeps the same variables
156	2210	Node bvl = nm->mkNode(BOUND_VAR_LIST, ovars);
157		// update the predicate
158	1105	pred = nm->mkNode(EXISTS, bvl, pred);
159		}
160	2278	Trace("sk-manager-debug") << "call sub mkSkolem" << std::endl;
161		// don't use a proof generator, since this may be an intermediate, partially
162		// skolemized formula.
163	2278	Node k = mkSkolem(v, pred, prefix, comment, flags, nullptr);
164	2278	Assert(k.getType() == v.getType());
165	4556	TNode tv = v;
166	4556	TNode tk = k;
167	4556	Trace("sk-manager-debug")
168	2278	<< "qskolem apply " << tv << " -> " << tk << " to " << pred << std::endl;
169		// the quantified formula with one step of skolemization
170	2278	qskolem = pred.substitute(tv, tk);
171	2278	Trace("sk-manager-debug") << "qskolem done substitution" << std::endl;
172	4556	return k;
173		}
174
175	45680	Node SkolemManager::mkPurifySkolem(Node t,
176		const std::string& prefix,
177		const std::string& comment,
178		int flags)
179		{
180	91360	Node to = getOriginalForm(t);
181		// We do not currently insist that to does not contain witness terms
182
183	45680	Node k = mkSkolemInternal(to, prefix, comment, flags);
184		// set original form attribute for k
185		OriginalFormAttribute ofa;
186	45680	k.setAttribute(ofa, to);
187
188	91360	Trace("sk-manager-skolem")
189	45680	<< "skolem: " << k << " purify " << to << std::endl;
190	91360	return k;
191		}
192
193	3173	Node SkolemManager::mkSkolemFunction(SkolemFunId id, TypeNode tn, Node cacheVal)
194		{
195	6346	std::tuple<SkolemFunId, TypeNode, Node> key(id, tn, cacheVal);
196		std::map<std::tuple<SkolemFunId, TypeNode, Node>, Node>::iterator it =
197	3173	d_skolemFuns.find(key);
198	3173	if (it == d_skolemFuns.end())
199		{
200	748	NodeManager* nm = NodeManager::currentNM();
201	1496	std::stringstream ss;
202	748	ss << "SKOLEM_FUN_" << id;
203	1496	Node k = nm->mkSkolem(ss.str(), tn, "an internal skolem function");
204	748	d_skolemFuns[key] = k;
205	748	return k;
206		}
207	2425	return it->second;
208		}
209
210	115912	Node SkolemManager::mkDummySkolem(const std::string& prefix,
211		const TypeNode& type,
212		const std::string& comment,
213		int flags)
214		{
215	115912	return NodeManager::currentNM()->mkSkolem(prefix, type, comment, flags);
216		}
217
218	75	ProofGenerator* SkolemManager::getProofGenerator(Node t) const
219		{
220	75	std::map<Node, ProofGenerator*>::const_iterator it = d_gens.find(t);
221	75	if (it != d_gens.end())
222		{
223		return it->second;
224		}
225	75	return nullptr;
226		}
227
228	1554	Node SkolemManager::getWitnessForm(Node k)
229		{
230	1554	Assert(k.getKind() == SKOLEM);
231		// simply look up the witness form for k via an attribute
232		WitnessFormAttribute wfa;
233	1554	return k.getAttribute(wfa);
234		}
235
236	199428	Node SkolemManager::getOriginalForm(Node n)
237		{
238	199428	if (n.isNull())
239		{
240	4	return n;
241		}
242	398848	Trace("sk-manager-debug")
243	199424	<< "SkolemManager::getOriginalForm " << n << std::endl;
244		OriginalFormAttribute ofa;
245	199424	NodeManager* nm = NodeManager::currentNM();
246	398848	std::unordered_map<TNode, Node> visited;
247	199424	std::unordered_map<TNode, Node>::iterator it;
248	398848	std::vector<TNode> visit;
249	398848	TNode cur;
250	199424	visit.push_back(n);
251	561363	do
252		{
253	760787	cur = visit.back();
254	760787	visit.pop_back();
255	760787	it = visited.find(cur);
256
257	760787	if (it == visited.end())
258		{
259	507622	if (cur.hasAttribute(ofa))
260		{
261	327118	visited[cur] = cur.getAttribute(ofa);
262		}
263		else
264		{
265	180504	visited[cur] = Node::null();
266	180504	visit.push_back(cur);
267	180504	if (cur.getMetaKind() == metakind::PARAMETERIZED)
268		{
269	23009	visit.push_back(cur.getOperator());
270		}
271	538354	for (const Node& cn : cur)
272		{
273	357850	visit.push_back(cn);
274		}
275		}
276		}
277	253165	else if (it->second.isNull())
278		{
279	361008	Node ret = cur;
280	180504	bool childChanged = false;
281	361008	std::vector<Node> children;
282	180504	if (cur.getMetaKind() == metakind::PARAMETERIZED)
283		{
284	23009	it = visited.find(cur.getOperator());
285	23009	Assert(it != visited.end());
286	23009	Assert(!it->second.isNull());
287	23009	childChanged = childChanged \|\| cur.getOperator() != it->second;
288	23009	children.push_back(it->second);
289		}
290	538354	for (const Node& cn : cur)
291		{
292	357850	it = visited.find(cn);
293	357850	Assert(it != visited.end());
294	357850	Assert(!it->second.isNull());
295	357850	childChanged = childChanged \|\| cn != it->second;
296	357850	children.push_back(it->second);
297		}
298	180504	if (childChanged)
299		{
300	40399	ret = nm->mkNode(cur.getKind(), children);
301		}
302	180504	cur.setAttribute(ofa, ret);
303	180504	visited[cur] = ret;
304		}
305	760787	} while (!visit.empty());
306	199424	Assert(visited.find(n) != visited.end());
307	199424	Assert(!visited.find(n)->second.isNull());
308	199424	Trace("sk-manager-debug") << "..return " << visited[n] << std::endl;
309	199424	return visited[n];
310		}
311
312	50546	Node SkolemManager::mkSkolemInternal(Node w,
313		const std::string& prefix,
314		const std::string& comment,
315		int flags)
316		{
317		// note that witness, original forms are independent, but share skolems
318	50546	NodeManager* nm = NodeManager::currentNM();
319		// w is not necessarily a witness term
320		SkolemFormAttribute sfa;
321	101092	Node k;
322		// could already have a skolem if we used w already
323	50546	if (w.hasAttribute(sfa))
324		{
325	9492	return w.getAttribute(sfa);
326		}
327		// make the new skolem
328	41054	if (flags & NodeManager::SKOLEM_BOOL_TERM_VAR)
329		{
330	748	Assert (w.getType().isBoolean());
331	748	k = nm->mkBooleanTermVariable();
332		}
333		else
334		{
335	40306	k = nm->mkSkolem(prefix, w.getType(), comment, flags);
336		}
337		// set skolem form attribute for w
338	41054	w.setAttribute(sfa, k);
339	82108	Trace("sk-manager") << "SkolemManager::mkSkolem: " << k << " : " << w
340	41054	<< std::endl;
341	41054	return k;
342		}
343
344	27735	} // namespace cvc5