src/theory/quantifiers/sygus/synth_conjecture.h

   1 /*********************                                                        */
   2 /*! \file synth_conjecture.h
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Andrew Reynolds, Mathias Preiner, Haniel Barbosa
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2020 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
  11  **
  12  ** \brief Class that encapsulates techniques for a single (SyGuS) synthesis
  13  ** conjecture.
  14  **/
  15
  16 #include "cvc4_private.h"
  17
  18 #ifndef CVC4__THEORY__QUANTIFIERS__SYNTH_CONJECTURE_H
  19 #define CVC4__THEORY__QUANTIFIERS__SYNTH_CONJECTURE_H
  20
  21 #include <memory>
  22
  23 #include "theory/decision_manager.h"
  24 #include "theory/quantifiers/expr_miner_manager.h"
  25 #include "theory/quantifiers/sygus/ce_guided_single_inv.h"
  26 #include "theory/quantifiers/sygus/cegis.h"
  27 #include "theory/quantifiers/sygus/cegis_core_connective.h"
  28 #include "theory/quantifiers/sygus/cegis_unif.h"
  29 #include "theory/quantifiers/sygus/example_eval_cache.h"
  30 #include "theory/quantifiers/sygus/example_infer.h"
  31 #include "theory/quantifiers/sygus/sygus_grammar_cons.h"
  32 #include "theory/quantifiers/sygus/sygus_pbe.h"
  33 #include "theory/quantifiers/sygus/sygus_process_conj.h"
  34 #include "theory/quantifiers/sygus/sygus_repair_const.h"
  35 #include "theory/quantifiers/sygus/sygus_stats.h"
  36 #include "theory/quantifiers/sygus/template_infer.h"
  37
  38 namespace CVC4 {
  39 namespace theory {
  40 namespace quantifiers {
  41
  42 class SygusStatistics;
  43
  44 /**
  45  * A base class for generating values for actively-generated enumerators.
  46  * At a high level, the job of this class is to accept a stream of "abstract
  47  * values" a1, ..., an, ..., and generate a (possibly larger) stream of
  48  * "concrete values" c11, ..., c1{m_1}, ..., cn1, ... cn{m_n}, ....
  49  */
  50 class EnumValGenerator
  51 {
  52  public:
  53   virtual ~EnumValGenerator() {}
  54   /** initialize this class with enumerator e */
  55   virtual void initialize(Node e) = 0;
  56   /** Inform this generator that abstract value v was enumerated. */
  57   virtual void addValue(Node v) = 0;
  58   /**
  59    * Increment this value generator. If this returns false, then we are out of
  60    * values. If this returns true, getCurrent(), if non-null, returns the
  61    * current term.
  62    *
  63    * Notice that increment() may return true and afterwards it may be the case
  64    * getCurrent() is null. We do this so that increment() does not take too
  65    * much time per call, which can be the case for grammars where it is
  66    * difficult to find the next (non-redundant) term. Returning true with
  67    * a null current term gives the caller the chance to interleave other
  68    * reasoning.
  69    */
  70   virtual bool increment() = 0;
  71   /** Get the current concrete value generated by this class. */
  72   virtual Node getCurrent() = 0;
  73 };
  74
  75 /** a synthesis conjecture
  76  * This class implements approaches for a synthesis conjecture, given by data
  77  * member d_quant.
  78  * This includes both approaches for synthesis in Reynolds et al CAV 2015. It
  79  * determines which approach and optimizations are applicable to the
  80  * conjecture, and has interfaces for implementing them.
  81  */
  82 class SynthConjecture
  83 {
  84  public:
  85   SynthConjecture(QuantifiersEngine* qe,
  86                   QuantifiersState& qs,
  87                   SygusStatistics& s);
  88   ~SynthConjecture();
  89   /** presolve */
  90   void presolve();
  91   /** get original version of conjecture */
  92   Node getConjecture() const { return d_quant; }
  93   /** get deep embedding version of conjecture */
  94   Node getEmbeddedConjecture() const { return d_embed_quant; }
  95   //-------------------------------for counterexample-guided check/refine
  96   /** whether the conjecture is waiting for a call to doCheck below */
  97   bool needsCheck();
  98   /** whether the conjecture is waiting for a call to doRefine below */
  99   bool needsRefinement() const;
 100   /** do syntax-guided enumerative check
 101    *
 102    * This is step 2(a) of Figure 3 of Reynolds et al CAV 2015.
 103    *
 104    * The method returns true if this conjecture is finished trying solutions
 105    * for the given call to SynthEngine::check.
 106    *
 107    * Notice that we make multiple calls to doCheck on one call to
 108    * SynthEngine::check. For example, if we are using an actively-generated
 109    * enumerator, one enumerated (abstract) term may correspond to multiple
 110    * concrete terms t1, ..., tn to check, where we make up to n calls to doCheck
 111    * when each of t1, ..., tn fails to satisfy the current refinement lemmas.
 112    */
 113   bool doCheck(std::vector<Node>& lems);
 114   /** do refinement
 115    *
 116    * This is step 2(b) of Figure 3 of Reynolds et al CAV 2015.
 117    *
 118    * This method is run when needsRefinement() returns true, indicating that
 119    * the last call to doCheck found a counterexample to the last candidate.
 120    *
 121    * This method adds a refinement lemma on the output channel of quantifiers
 122    * engine. If the refinement lemma is a duplicate, then we manually
 123    * exclude the current candidate via excludeCurrentSolution. This should
 124    * only occur when the synthesis conjecture for the current candidate fails
 125    * to evaluate to false for a given counterexample point, but regardless its
 126    * negation is satisfiable for the current candidate and that point. This is
 127    * exclusive to theories with partial functions, e.g. (non-linear) division.
 128    *
 129    * This method returns true if a lemma was added on the output channel, and
 130    * false otherwise.
 131    */
 132   bool doRefine();
 133   //-------------------------------end for counterexample-guided check/refine
 134   /**
 135    * Prints the synthesis solution to output stream out. This invokes solution
 136    * reconstruction if the conjecture is single invocation. Otherwise, it
 137    * returns the solution found by sygus enumeration.
 138    */
 139   void printSynthSolution(std::ostream& out);
 140   /** get synth solutions
 141    *
 142    * This method returns true if this class has a solution available to the
 143    * conjecture that it was assigned.
 144    *
 145    * Let q be the synthesis conjecture assigned to this class.
 146    * This method adds entries to sol_map[q] that map functions-to-synthesize to
 147    * their builtin solution, which has the same type. For example, for synthesis
 148    * conjecture exists f. forall x. f( x )>x, this function will update
 149    * sol_map[q] to contain the entry:
 150    *   f -> (lambda x. x+1)
 151    */
 152   bool getSynthSolutions(std::map<Node, std::map<Node, Node> >& sol_map);
 153   /**
 154    * The feasible guard whose semantics are "this conjecture is feasiable".
 155    * This is "G" in Figure 3 of Reynolds et al CAV 2015.
 156    */
 157   Node getGuard() const;
 158   /** is ground */
 159   bool isGround() { return d_inner_vars.empty(); }
 160   /** are we using single invocation techniques */
 161   bool isSingleInvocation() const;
 162   /** preregister conjecture
 163    * This is used as a heuristic for solution reconstruction, so that we
 164    * remember expressions in the conjecture before preprocessing, since they
 165    * may be helpful during solution reconstruction (Figure 5 of Reynolds et al
 166    * CAV 2015)
 167    */
 168   void preregisterConjecture(Node q);
 169   /** assign conjecture q to this class */
 170   void assign(Node q);
 171   /** has a conjecture been assigned to this class */
 172   bool isAssigned() { return !d_embed_quant.isNull(); }
 173   /**
 174    * Get model value for term n.
 175    */
 176   Node getModelValue(Node n);
 177
 178   /** get utility for static preprocessing and analysis of conjectures */
 179   SynthConjectureProcess* getProcess() { return d_ceg_proc.get(); }
 180   /** get constant repair utility */
 181   SygusRepairConst* getRepairConst() { return d_sygus_rconst.get(); }
 182   /** get example inference utility */
 183   ExampleInfer* getExampleInfer() { return d_exampleInfer.get(); }
 184   /** get the example evaluation cache utility for enumerator e */
 185   ExampleEvalCache* getExampleEvalCache(Node e);
 186   /** get program by examples module */
 187   SygusPbe* getPbe() { return d_ceg_pbe.get(); }
 188   /** get the symmetry breaking predicate for type */
 189   Node getSymmetryBreakingPredicate(
 190       Node x, Node e, TypeNode tn, unsigned tindex, unsigned depth);
 191   /** print out debug information about this conjecture */
 192   void debugPrint(const char* c);
 193   /** check side condition
 194    *
 195    * This returns false if the solution { d_candidates -> cvals } does not
 196    * satisfy the side condition of the conjecture maintained by this class,
 197    * if it exists, and true otherwise.
 198    */
 199   bool checkSideCondition(const std::vector<Node>& cvals) const;
 200
 201  private:
 202   /** reference to quantifier engine */
 203   QuantifiersEngine* d_qe;
 204   /** Reference to the quantifiers state */
 205   QuantifiersState& d_qstate;
 206   /** reference to the statistics of parent */
 207   SygusStatistics& d_stats;
 208   /** term database sygus of d_qe */
 209   TermDbSygus* d_tds;
 210   /** The feasible guard. */
 211   Node d_feasible_guard;
 212   /**
 213    * Do we have a solution in this solve context? This flag is reset to false
 214    * on every call to presolve.
 215    */
 216   bool d_hasSolution;
 217   /** the decision strategy for the feasible guard */
 218   std::unique_ptr<DecisionStrategy> d_feasible_strategy;
 219   /** single invocation utility */
 220   std::unique_ptr<CegSingleInv> d_ceg_si;
 221   /** template inference utility */
 222   std::unique_ptr<SygusTemplateInfer> d_templInfer;
 223   /** utility for static preprocessing and analysis of conjectures */
 224   std::unique_ptr<SynthConjectureProcess> d_ceg_proc;
 225   /** grammar utility */
 226   std::unique_ptr<CegGrammarConstructor> d_ceg_gc;
 227   /** repair constant utility */
 228   std::unique_ptr<SygusRepairConst> d_sygus_rconst;
 229   /** example inference utility */
 230   std::unique_ptr<ExampleInfer> d_exampleInfer;
 231   /** example evaluation cache utility for each enumerator */
 232   std::map<Node, std::unique_ptr<ExampleEvalCache> > d_exampleEvalCache;
 233
 234   //------------------------modules
 235   /** program by examples module */
 236   std::unique_ptr<SygusPbe> d_ceg_pbe;
 237   /** CEGIS module */
 238   std::unique_ptr<Cegis> d_ceg_cegis;
 239   /** CEGIS UNIF module */
 240   std::unique_ptr<CegisUnif> d_ceg_cegisUnif;
 241   /** connective core utility */
 242   std::unique_ptr<CegisCoreConnective> d_sygus_ccore;
 243   /** the set of active modules (subset of the above list) */
 244   std::vector<SygusModule*> d_modules;
 245   /** master module
 246    *
 247    * This is the module (one of those above) that takes sole responsibility
 248    * for this conjecture, determined during assign(...).
 249    */
 250   SygusModule* d_master;
 251   //------------------------end modules
 252
 253   //------------------------enumerators
 254   /**
 255    * Get model values for terms n, store in vector v. This method returns true
 256    * if and only if all values added to v are non-null.
 257    *
 258    * The argument activeIncomplete indicates whether n contains an active
 259    * enumerator that is currently not finished enumerating values, but returned
 260    * null on a call to getEnumeratedValue. This value is used for determining
 261    * whether we should call getEnumeratedValues again within a call to
 262    * SynthConjecture::check.
 263    *
 264    * It removes terms from n that correspond to "inactive" enumerators, that
 265    * is, enumerators whose values have been exhausted.
 266    */
 267   bool getEnumeratedValues(std::vector<Node>& n,
 268                            std::vector<Node>& v,
 269                            bool& activeIncomplete);
 270   /**
 271    * Get model value for term n. If n has a value that was excluded by
 272    * datatypes sygus symmetry breaking, this method returns null. It sets
 273    * activeIncomplete to true if there is an actively-generated enumerator whose
 274    * current value is null but it has not finished generating values.
 275    */
 276   Node getEnumeratedValue(Node n, bool& activeIncomplete);
 277   /** enumerator generators for each actively-generated enumerator */
 278   std::map<Node, std::unique_ptr<EnumValGenerator> > d_evg;
 279   /**
 280    * Map from enumerators to whether they are currently being
 281    * "actively-generated". That is, we are in a state where we have called
 282    * d_evg[e].addValue(v) for some v, and d_evg[e].getNext() has not yet
 283    * returned null. The range of this map stores the abstract value that
 284    * we are currently generating values from.
 285    */
 286   std::map<Node, Node> d_ev_curr_active_gen;
 287   /** the current waiting value of each actively-generated enumerator, if any
 288    *
 289    * This caches values that are actively generated and that we have not yet
 290    * passed to a call to SygusModule::constructCandidates. An example of when
 291    * this may occur is when there are two actively-generated enumerators e1 and
 292    * e2. Say on some iteration we actively-generate v1 for e1, the value
 293    * of e2 was excluded by symmetry breaking, and say the current master sygus
 294    * module does not handle partial models. Hence, we abort the current check.
 295    * We remember that the value of e1 was v1 by storing it here, so that on
 296    * a future check when v2 has a proper value, it is returned.
 297    */
 298   std::map<Node, Node> d_ev_active_gen_waiting;
 299   /** the first value enumerated for each actively-generated enumerator
 300    *
 301    * This is to implement an optimization that only guards the blocking lemma
 302    * for the first value of an actively-generated enumerator.
 303    */
 304   std::map<Node, Node> d_ev_active_gen_first_val;
 305   //------------------------end enumerators
 306
 307   /** list of constants for quantified formula
 308    * The outer Skolems for the negation of d_embed_quant.
 309    */
 310   std::vector<Node> d_candidates;
 311   /** base instantiation
 312    * If d_embed_quant is forall d. exists y. P( d, y ), then
 313    * this is the formula  exists y. P( d_candidates, y ). Notice that
 314    * (exists y. F) is shorthand above for ~( forall y. ~F ).
 315    */
 316   Node d_base_inst;
 317   /** list of variables on inner quantification */
 318   std::vector<Node> d_inner_vars;
 319   /**
 320    * The set of skolems for the current "verification" lemma, if one exists.
 321    * This may be added to during calls to doCheck(). The model values for these
 322    * skolems are analyzed during doRefine().
 323    */
 324   std::vector<Node> d_ce_sk_vars;
 325   /**
 326    * If we have already tested the satisfiability of the current verification
 327    * lemma, this stores the model values of d_ce_sk_vars in the current
 328    * (satisfiable, failed) verification lemma.
 329    */
 330   std::vector<Node> d_ce_sk_var_mvs;
 331   /**
 332    * Whether the above vector has been set. We have this flag since the above
 333    * vector may be set to empty (e.g. for ground synthesis conjectures).
 334    */
 335   bool d_set_ce_sk_vars;
 336
 337   /** the asserted (negated) conjecture */
 338   Node d_quant;
 339   /**
 340    * The side condition for solving the conjecture, after conversion to deep
 341    * embedding.
 342    */
 343   Node d_embedSideCondition;
 344   /** (negated) conjecture after simplification */
 345   Node d_simp_quant;
 346   /** (negated) conjecture after simplification, conversion to deep embedding */
 347   Node d_embed_quant;
 348   /** candidate information */
 349   class CandidateInfo
 350   {
 351    public:
 352     CandidateInfo() {}
 353     /** list of terms we have instantiated candidates with */
 354     std::vector<Node> d_inst;
 355   };
 356   std::map<Node, CandidateInfo> d_cinfo;
 357   /**
 358    * The first index of an instantiation in CandidateInfo::d_inst that we have
 359    * not yet tried to repair.
 360    */
 361   unsigned d_repair_index;
 362   /** number of times we have called doRefine */
 363   unsigned d_refine_count;
 364   /** record solution (this is used to construct solutions later) */
 365   void recordSolution(std::vector<Node>& vs);
 366   /** get synth solutions internal
 367    *
 368    * This function constructs the body of solutions for all
 369    * functions-to-synthesize in this conjecture and stores them in sols, in
 370    * order. For each solution added to sols, we add an integer indicating what
 371    * kind of solution n is, where if sols[i] = n, then
 372    *   if status[i] = 0: n is the (builtin term) corresponding to the solution,
 373    *   if status[i] = 1: n is the sygus representation of the solution.
 374    * We store builtin versions under some conditions (such as when the sygus
 375    * grammar is being ignored).
 376    *
 377    * This consults the single invocation module to get synthesis solutions if
 378    * isSingleInvocation() returns true.
 379    *
 380    * For example, for conjecture exists fg. forall x. f(x)>g(x), this function
 381    * may set ( sols, status ) to ( { x+1, d_x() }, { 1, 0 } ), where d_x() is
 382    * the sygus datatype constructor corresponding to variable x.
 383    */
 384   bool getSynthSolutionsInternal(std::vector<Node>& sols,
 385                                  std::vector<int>& status);
 386   //-------------------------------- sygus stream
 387   /**
 388    * Prints the current synthesis solution to the output stream indicated by
 389    * the Options object, send a lemma blocking the current solution to the
 390    * output channel, which we refer to as a "stream exclusion lemma".
 391    *
 392    * The argument enums is the set of enumerators that comprise the current
 393    * solution, and values is their current values.
 394    */
 395   void printAndContinueStream(const std::vector<Node>& enums,
 396                               const std::vector<Node>& values);
 397   /** exclude the current solution { enums -> values } */
 398   void excludeCurrentSolution(const std::vector<Node>& enums,
 399                               const std::vector<Node>& values);
 400   /**
 401    * Whether we have guarded a stream exclusion lemma when using sygusStream.
 402    * This is an optimization that allows us to guard only the first stream
 403    * exclusion lemma.
 404    */
 405   bool d_guarded_stream_exc;
 406   //-------------------------------- end sygus stream
 407   /** expression miner managers for each function-to-synthesize
 408    *
 409    * Notice that for each function-to-synthesize, we enumerate a stream of
 410    * candidate solutions, where each of these streams is independent. Thus,
 411    * we maintain separate expression miner managers for each of them.
 412    *
 413    * This is used for the sygusRewSynth() option to synthesize new candidate
 414    * rewrite rules.
 415    */
 416   std::map<Node, ExpressionMinerManager> d_exprm;
 417 };
 418
 419 }  // namespace quantifiers
 420 }  // namespace theory
 421 } /* namespace CVC4 */
 422
 423 #endif