Head

GCC Code Coverage Report

Directory:	.		Exec	Total	Coverage
File:	src/expr/skolem_manager.cpp	Lines:	155	158	98.1 %
Date:	2021-05-22	Branches:	309	746	41.4 %


/******************************************************************************
 * 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::SHARED_SELECTOR: return "SHARED_SELECTOR";
    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,
                                     int flags)
{
  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", flags);
    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	2653	const char* toString(SkolemFunId id)
46		{
47	2653	switch (id)
48		{
49	81	case SkolemFunId::DIV_BY_ZERO: return "DIV_BY_ZERO";
50	61	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	565	case SkolemFunId::SELECTOR_WRONG: return "SELECTOR_WRONG";
54	1885	case SkolemFunId::SHARED_SELECTOR: return "SHARED_SELECTOR";
55	18	case SkolemFunId::SEQ_NTH_OOB: return "SEQ_NTH_OOB";
56		default: return "?";
57		}
58		}
59
60	2653	std::ostream& operator<<(std::ostream& out, SkolemFunId id)
61		{
62	2653	out << toString(id);
63	2653	return out;
64		}
65
66	5112	Node SkolemManager::mkSkolem(Node v,
67		Node pred,
68		const std::string& prefix,
69		const std::string& comment,
70		int flags,
71		ProofGenerator* pg)
72		{
73		// We do not currently insist that pred does not contain witness terms
74	5112	Assert(v.getKind() == BOUND_VARIABLE);
75		// make the witness term
76	5112	NodeManager* nm = NodeManager::currentNM();
77	10224	Node bvl = nm->mkNode(BOUND_VAR_LIST, v);
78		// Make the witness term, where notice that pred may contain skolems. We do
79		// not recursively convert pred to witness form, since witness terms should
80		// be treated as opaque. Moreover, the use of witness forms leads to
81		// variable shadowing issues in e.g. skolemization.
82	10224	Node w = nm->mkNode(WITNESS, bvl, pred);
83		// store the mapping to proof generator if it exists
84	5112	if (pg != nullptr)
85		{
86		// We cache based on the existential of the original predicate
87	3458	Node q = nm->mkNode(EXISTS, bvl, pred);
88		// Notice this may overwrite an existing proof generator. This does not
89		// matter since either should be able to prove q.
90	1729	d_gens[q] = pg;
91		}
92	5112	Node k = mkSkolemInternal(w, prefix, comment, flags);
93		// set witness form attribute for k
94		WitnessFormAttribute wfa;
95	5112	k.setAttribute(wfa, w);
96	10224	Trace("sk-manager-skolem")
97	5112	<< "skolem: " << k << " witness " << w << std::endl;
98	10224	return k;
99		}
100
101	1170	Node SkolemManager::mkSkolemize(Node q,
102		std::vector<Node>& skolems,
103		const std::string& prefix,
104		const std::string& comment,
105		int flags,
106		ProofGenerator* pg)
107		{
108	1170	Trace("sk-manager-debug") << "mkSkolemize " << q << std::endl;
109	1170	Assert(q.getKind() == EXISTS);
110	1170	Node currQ = q;
111	3451	for (const Node& av : q[0])
112		{
113	2281	Assert(currQ.getKind() == EXISTS && av == currQ[0][0]);
114		// currQ is updated to the result of skolemizing its first variable in
115		// the method below.
116	4562	Node sk = skolemize(currQ, currQ, prefix, comment, flags);
117	4562	Trace("sk-manager-debug")
118	2281	<< "made skolem " << sk << " for " << av << std::endl;
119	2281	skolems.push_back(sk);
120		}
121	1170	if (pg != nullptr)
122		{
123		// Same as above, this may overwrite an existing proof generator
124		d_gens[q] = pg;
125		}
126	1170	Trace("sk-manager-debug") << "...mkSkolemize returns " << currQ << std::endl;
127	1170	return currQ;
128		}
129
130	2281	Node SkolemManager::skolemize(Node q,
131		Node& qskolem,
132		const std::string& prefix,
133		const std::string& comment,
134		int flags)
135		{
136	2281	Assert(q.getKind() == EXISTS);
137	4562	Node v;
138	4562	std::vector<Node> ovars;
139	2281	Trace("sk-manager-debug") << "mkSkolemize..." << std::endl;
140	2281	NodeManager* nm = NodeManager::currentNM();
141	7326	for (const Node& av : q[0])
142		{
143	9607	if (v.isNull())
144		{
145	2281	v = av;
146	2281	continue;
147		}
148	5045	ovars.push_back(av);
149		}
150	2281	Assert(!v.isNull());
151		// make the predicate with one variable stripped off
152	4562	Node pred = q[1];
153	2281	Trace("sk-manager-debug") << "make exists predicate" << std::endl;
154	2281	if (!ovars.empty())
155		{
156		// keeps the same variables
157	2222	Node bvl = nm->mkNode(BOUND_VAR_LIST, ovars);
158		// update the predicate
159	1111	pred = nm->mkNode(EXISTS, bvl, pred);
160		}
161	2281	Trace("sk-manager-debug") << "call sub mkSkolem" << std::endl;
162		// don't use a proof generator, since this may be an intermediate, partially
163		// skolemized formula.
164	2281	Node k = mkSkolem(v, pred, prefix, comment, flags, nullptr);
165	2281	Assert(k.getType() == v.getType());
166	4562	TNode tv = v;
167	4562	TNode tk = k;
168	4562	Trace("sk-manager-debug")
169	2281	<< "qskolem apply " << tv << " -> " << tk << " to " << pred << std::endl;
170		// the quantified formula with one step of skolemization
171	2281	qskolem = pred.substitute(tv, tk);
172	2281	Trace("sk-manager-debug") << "qskolem done substitution" << std::endl;
173	4562	return k;
174		}
175
176	48357	Node SkolemManager::mkPurifySkolem(Node t,
177		const std::string& prefix,
178		const std::string& comment,
179		int flags)
180		{
181	96714	Node to = getOriginalForm(t);
182		// We do not currently insist that to does not contain witness terms
183
184	48357	Node k = mkSkolemInternal(to, prefix, comment, flags);
185		// set original form attribute for k
186		OriginalFormAttribute ofa;
187	48357	k.setAttribute(ofa, to);
188
189	96714	Trace("sk-manager-skolem")
190	48357	<< "skolem: " << k << " purify " << to << std::endl;
191	96714	return k;
192		}
193
194	5685	Node SkolemManager::mkSkolemFunction(SkolemFunId id,
195		TypeNode tn,
196		Node cacheVal,
197		int flags)
198		{
199	11370	std::tuple<SkolemFunId, TypeNode, Node> key(id, tn, cacheVal);
200		std::map<std::tuple<SkolemFunId, TypeNode, Node>, Node>::iterator it =
201	5685	d_skolemFuns.find(key);
202	5685	if (it == d_skolemFuns.end())
203		{
204	2653	NodeManager* nm = NodeManager::currentNM();
205	5306	std::stringstream ss;
206	2653	ss << "SKOLEM_FUN_" << id;
207	5306	Node k = nm->mkSkolem(ss.str(), tn, "an internal skolem function", flags);
208	2653	d_skolemFuns[key] = k;
209	2653	return k;
210		}
211	3032	return it->second;
212		}
213
214	114050	Node SkolemManager::mkDummySkolem(const std::string& prefix,
215		const TypeNode& type,
216		const std::string& comment,
217		int flags)
218		{
219	114050	return NodeManager::currentNM()->mkSkolem(prefix, type, comment, flags);
220		}
221
222	75	ProofGenerator* SkolemManager::getProofGenerator(Node t) const
223		{
224	75	std::map<Node, ProofGenerator*>::const_iterator it = d_gens.find(t);
225	75	if (it != d_gens.end())
226		{
227		return it->second;
228		}
229	75	return nullptr;
230		}
231
232	1786	Node SkolemManager::getWitnessForm(Node k)
233		{
234	1786	Assert(k.getKind() == SKOLEM);
235		// simply look up the witness form for k via an attribute
236		WitnessFormAttribute wfa;
237	1786	return k.getAttribute(wfa);
238		}
239
240	209921	Node SkolemManager::getOriginalForm(Node n)
241		{
242	209921	if (n.isNull())
243		{
244	4	return n;
245		}
246	419834	Trace("sk-manager-debug")
247	209917	<< "SkolemManager::getOriginalForm " << n << std::endl;
248		OriginalFormAttribute ofa;
249	209917	NodeManager* nm = NodeManager::currentNM();
250	419834	std::unordered_map<TNode, Node> visited;
251	209917	std::unordered_map<TNode, Node>::iterator it;
252	419834	std::vector<TNode> visit;
253	419834	TNode cur;
254	209917	visit.push_back(n);
255	594445	do
256		{
257	804362	cur = visit.back();
258	804362	visit.pop_back();
259	804362	it = visited.find(cur);
260
261	804362	if (it == visited.end())
262		{
263	537507	if (cur.hasAttribute(ofa))
264		{
265	346755	visited[cur] = cur.getAttribute(ofa);
266		}
267		else
268		{
269	190752	visited[cur] = Node::null();
270	190752	visit.push_back(cur);
271	190752	if (cur.getMetaKind() == metakind::PARAMETERIZED)
272		{
273	27156	visit.push_back(cur.getOperator());
274		}
275	567289	for (const Node& cn : cur)
276		{
277	376537	visit.push_back(cn);
278		}
279		}
280		}
281	266855	else if (it->second.isNull())
282		{
283	381504	Node ret = cur;
284	190752	bool childChanged = false;
285	381504	std::vector<Node> children;
286	190752	if (cur.getMetaKind() == metakind::PARAMETERIZED)
287		{
288	27156	it = visited.find(cur.getOperator());
289	27156	Assert(it != visited.end());
290	27156	Assert(!it->second.isNull());
291	27156	childChanged = childChanged \|\| cur.getOperator() != it->second;
292	27156	children.push_back(it->second);
293		}
294	567289	for (const Node& cn : cur)
295		{
296	376537	it = visited.find(cn);
297	376537	Assert(it != visited.end());
298	376537	Assert(!it->second.isNull());
299	376537	childChanged = childChanged \|\| cn != it->second;
300	376537	children.push_back(it->second);
301		}
302	190752	if (childChanged)
303		{
304	47506	ret = nm->mkNode(cur.getKind(), children);
305		}
306	190752	cur.setAttribute(ofa, ret);
307	190752	visited[cur] = ret;
308		}
309	804362	} while (!visit.empty());
310	209917	Assert(visited.find(n) != visited.end());
311	209917	Assert(!visited.find(n)->second.isNull());
312	209917	Trace("sk-manager-debug") << "..return " << visited[n] << std::endl;
313	209917	return visited[n];
314		}
315
316	53469	Node SkolemManager::mkSkolemInternal(Node w,
317		const std::string& prefix,
318		const std::string& comment,
319		int flags)
320		{
321		// note that witness, original forms are independent, but share skolems
322	53469	NodeManager* nm = NodeManager::currentNM();
323		// w is not necessarily a witness term
324		SkolemFormAttribute sfa;
325	106938	Node k;
326		// could already have a skolem if we used w already
327	53469	if (w.hasAttribute(sfa))
328		{
329	9716	return w.getAttribute(sfa);
330		}
331		// make the new skolem
332	43753	if (flags & NodeManager::SKOLEM_BOOL_TERM_VAR)
333		{
334	775	Assert (w.getType().isBoolean());
335	775	k = nm->mkBooleanTermVariable();
336		}
337		else
338		{
339	42978	k = nm->mkSkolem(prefix, w.getType(), comment, flags);
340		}
341		// set skolem form attribute for w
342	43753	w.setAttribute(sfa, k);
343	87506	Trace("sk-manager") << "SkolemManager::mkSkolem: " << k << " : " << w
344	43753	<< std::endl;
345	43753	return k;
346		}
347
348	28194	} // namespace cvc5