1 /********************* */
2 /*! \file output_channel.h
4 ** Top contributors (to current version):
5 ** Morgan Deters, Liana Hadarean, Tim King
6 ** This file is part of the CVC4 project.
7 ** Copyright (c) 2009-2017 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.\endverbatim
12 ** \brief The theory output channel interface
14 ** The theory output channel interface.
17 #include "cvc4_private.h"
19 #ifndef __CVC4__THEORY__OUTPUT_CHANNEL_H
20 #define __CVC4__THEORY__OUTPUT_CHANNEL_H
24 #include "base/cvc4_assert.h"
25 #include "proof/proof_manager.h"
26 #include "smt/logic_exception.h"
27 #include "theory/interrupted.h"
28 #include "util/proof.h"
29 #include "util/resource_manager.h"
37 * A LemmaStatus, returned from OutputChannel::lemma(), provides information
38 * about the lemma added. In particular, it contains the T-rewritten lemma
39 * for inspection and the user-level at which the lemma will reside.
43 LemmaStatus(TNode rewrittenLemma
, unsigned level
)
44 : d_rewrittenLemma(rewrittenLemma
), d_level(level
) {}
46 /** Get the T-rewritten form of the lemma. */
47 TNode
getRewrittenLemma() const { return d_rewrittenLemma
; }
49 * Get the user-level at which the lemma resides. After this user level
50 * is popped, the lemma is un-asserted from the SAT layer. This level
51 * will be 0 if the lemma didn't reach the SAT layer at all.
53 unsigned getLevel() const { return d_level
; }
55 Node d_rewrittenLemma
;
57 }; /* class LemmaStatus */
60 * Generic "theory output channel" interface.
62 * All methods can throw unrecoverable CVC4::Exception's unless otherwise
67 /** Construct an OutputChannel. */
71 * Destructs an OutputChannel. This implementation does nothing,
72 * but we need a virtual destructor for safety in case subclasses
75 virtual ~OutputChannel() {}
77 OutputChannel(const OutputChannel
&) = delete;
78 OutputChannel
& operator=(const OutputChannel
&) = delete;
81 * With safePoint(), the theory signals that it is at a safe point
82 * and can be interrupted.
84 * @throws Interrupted if the theory can be safely interrupted.
86 virtual void safePoint(uint64_t amount
) {}
89 * Indicate a theory conflict has arisen.
91 * @param n - a conflict at the current decision level. This should
92 * be an AND-kinded node of literals that are TRUE in the current
93 * assignment and are in conflict (i.e., at least one must be
94 * assigned false), or else a literal by itself (in the case of a
95 * unit conflict) which is assigned TRUE (and T-conflicting) in the
97 * @param pf - a proof of the conflict. This is only non-null if proofs
100 virtual void conflict(TNode n
, std::unique_ptr
<Proof
> pf
= nullptr) = 0;
103 * Propagate a theory literal.
105 * @param n - a theory consequence at the current decision level
106 * @return false if an immediate conflict was encountered
108 virtual bool propagate(TNode n
) = 0;
111 * Tell the core that a valid theory lemma at decision level 0 has
112 * been detected. (This requests a split.)
114 * @param n - a theory lemma valid at decision level 0
115 * @param rule - the proof rule for this lemma
116 * @param removable - whether the lemma can be removed at any point
117 * @param preprocess - whether to apply more aggressive preprocessing
118 * @param sendAtoms - whether to ensure atoms are sent to the theory
119 * @return the "status" of the lemma, including user level at which
120 * the lemma resides; the lemma will be removed when this user level pops
122 virtual LemmaStatus
lemma(TNode n
, ProofRule rule
, bool removable
= false,
123 bool preprocess
= false,
124 bool sendAtoms
= false) = 0;
127 * Variant of the lemma function that does not require providing a proof rule.
129 virtual LemmaStatus
lemma(TNode n
, bool removable
= false,
130 bool preprocess
= false, bool sendAtoms
= false) {
131 return lemma(n
, RULE_INVALID
, removable
, preprocess
, sendAtoms
);
135 * Request a split on a new theory atom. This is equivalent to
136 * calling lemma({OR n (NOT n)}).
138 * @param n - a theory atom; must be of Boolean type
140 LemmaStatus
split(TNode n
) { return splitLemma(n
.orNode(n
.notNode())); }
142 virtual LemmaStatus
splitLemma(TNode n
, bool removable
= false) = 0;
145 * If a decision is made on n, it must be in the phase specified.
146 * Note that this is enforced *globally*, i.e., it is completely
147 * context-INdependent. If you ever requirePhase() on a literal,
148 * it is phase-locked forever and ever. If it is to ever have the
149 * other phase as its assignment, it will be because it has been
150 * propagated that way (or it's a unit, at decision level 0).
152 * @param n - a theory atom with a SAT literal assigned; must have
153 * been pre-registered
154 * @param phase - the phase to decide on n
156 virtual void requirePhase(TNode n
, bool phase
) = 0;
159 * Flips the most recent unflipped decision to the other phase and
160 * returns true. If all decisions have been flipped, the root
161 * decision is re-flipped and flipDecision() returns false. If no
162 * decisions (flipped nor unflipped) are on the decision stack, the
163 * state is not affected and flipDecision() returns false.
165 * For example, if l1, l2, and l3 are all decision literals, and
166 * have been decided in positive phase, a series of flipDecision()
167 * calls has the following effects:
173 * l1 (and flipDecision() returns false)
175 * Naturally, flipDecision() might be interleaved with search. For example:
178 * flipDecision() <br/>
180 * flipDecision() <br/>
182 * SAT decides l3 <br/>
184 * flipDecision() <br/>
186 * flipDecision() <br/>
188 * SAT decides l2 <br/>
190 * flipDecision() <br/>
192 * flipDecision() returns FALSE<br/>
195 * @return true if a decision was flipped; false if no decision
196 * could be flipped, or if the root decision was re-flipped
198 virtual bool flipDecision() = 0;
201 * Notification from a theory that it realizes it is incomplete at
202 * this context level. If SAT is later determined by the
203 * TheoryEngine, it should actually return an UNKNOWN result.
205 virtual void setIncomplete() = 0;
208 * "Spend" a "resource." The meaning is specific to the context in
209 * which the theory is operating, and may even be ignored. The
210 * intended meaning is that if the user has set a limit on the "units
211 * of resource" that can be expended in a search, and that limit is
212 * exceeded, then the search is terminated. Note that the check for
213 * termination occurs in the main search loop, so while theories
214 * should call OutputChannel::spendResource() during particularly
215 * long-running operations, they cannot rely on resource() to break
216 * out of infinite or intractable computations.
218 virtual void spendResource(unsigned amount
) {}
221 * Handle user attribute.
222 * Associates theory t with the attribute attr. Theory t will be
223 * notified whenever an attribute of name attr is set on a node.
224 * This can happen through, for example, the SMT-LIBv2 language.
226 virtual void handleUserAttribute(const char* attr
, Theory
* t
) {}
228 /** Demands that the search restart from sat search level 0.
229 * Using this leads to non-termination issues.
230 * It is appropriate for prototyping for theories.
232 virtual void demandRestart() {}
234 }; /* class OutputChannel */
236 } // namespace theory
239 #endif /* __CVC4__THEORY__OUTPUT_CHANNEL_H */