src/theory/quantifiers/sygus/synth_conjecture.h

   1 /*********************                                                        */
   2 /*! \file synth_conjecture.h
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Andrew Reynolds, Haniel Barbosa, Tim King
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2019 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/sygus_grammar_cons.h"
  30 #include "theory/quantifiers/sygus/sygus_pbe.h"
  31 #include "theory/quantifiers/sygus/sygus_process_conj.h"
  32 #include "theory/quantifiers/sygus/sygus_repair_const.h"
  33 #include "theory/quantifiers/sygus/sygus_stats.h"
  34
  35 namespace CVC4 {
  36 namespace theory {
  37 namespace quantifiers {
  38
  39 class SynthEngine;
  40
  41 /**
  42  * A base class for generating values for actively-generated enumerators.
  43  * At a high level, the job of this class is to accept a stream of "abstract
  44  * values" a1, ..., an, ..., and generate a (possibly larger) stream of
  45  * "concrete values" c11, ..., c1{m_1}, ..., cn1, ... cn{m_n}, ....
  46  */
  47 class EnumValGenerator
  48 {
  49  public:
  50   virtual ~EnumValGenerator() {}
  51   /** initialize this class with enumerator e */
  52   virtual void initialize(Node e) = 0;
  53   /** Inform this generator that abstract value v was enumerated. */
  54   virtual void addValue(Node v) = 0;
  55   /**
  56    * Increment this value generator. If this returns false, then we are out of
  57    * values. If this returns true, getCurrent(), if non-null, returns the
  58    * current term.
  59    */
  60   virtual bool increment() = 0;
  61   /** Get the current concrete value generated by this class. */
  62   virtual Node getCurrent() = 0;
  63 };
  64
  65 /** a synthesis conjecture
  66  * This class implements approaches for a synthesis conecjture, given by data
  67  * member d_quant.
  68  * This includes both approaches for synthesis in Reynolds et al CAV 2015. It
  69  * determines which approach and optimizations are applicable to the
  70  * conjecture, and has interfaces for implementing them.
  71  */
  72 class SynthConjecture
  73 {
  74  public:
  75   SynthConjecture(QuantifiersEngine* qe, SynthEngine* p, SygusStatistics& s);
  76   ~SynthConjecture();
  77   /** presolve */
  78   void presolve();
  79   /** get original version of conjecture */
  80   Node getConjecture() { return d_quant; }
  81   /** get deep embedding version of conjecture */
  82   Node getEmbeddedConjecture() { return d_embed_quant; }
  83   //-------------------------------for counterexample-guided check/refine
  84   /** increment the number of times we have successfully done candidate
  85    * refinement */
  86   void incrementRefineCount() { d_refine_count++; }
  87   /** whether the conjecture is waiting for a call to doCheck below */
  88   bool needsCheck();
  89   /** whether the conjecture is waiting for a call to doRefine below */
  90   bool needsRefinement() const;
  91   /** do syntax-guided enumerative check
  92    *
  93    * This is step 2(a) of Figure 3 of Reynolds et al CAV 2015.
  94    *
  95    * The method returns true if this conjecture is finished trying solutions
  96    * for the given call to SynthEngine::check.
  97    *
  98    * Notice that we make multiple calls to doCheck on one call to
  99    * SynthEngine::check. For example, if we are using an actively-generated
 100    * enumerator, one enumerated (abstract) term may correspond to multiple
 101    * concrete terms t1, ..., tn to check, where we make up to n calls to doCheck
 102    * when each of t1, ..., tn fails to satisfy the current refinement lemmas.
 103    */
 104   bool doCheck(std::vector<Node>& lems);
 105   /** do refinement
 106    * This is step 2(b) of Figure 3 of Reynolds et al CAV 2015.
 107    */
 108   void doRefine(std::vector<Node>& lems);
 109   //-------------------------------end for counterexample-guided check/refine
 110   /**
 111    * Prints the synthesis solution to output stream out. This invokes solution
 112    * reconstruction if the conjecture is single invocation. Otherwise, it
 113    * returns the solution found by sygus enumeration.
 114    */
 115   void printSynthSolution(std::ostream& out);
 116   /** get synth solutions
 117    *
 118    * This method returns true if this class has a solution available to the
 119    * conjecture that it was assigned.
 120    *
 121    * Let q be the synthesis conjecture assigned to this class.
 122    * This method adds entries to sol_map[q] that map functions-to-synthesize to
 123    * their builtin solution, which has the same type. For example, for synthesis
 124    * conjecture exists f. forall x. f( x )>x, this function will update
 125    * sol_map[q] to contain the entry:
 126    *   f -> (lambda x. x+1)
 127    */
 128   bool getSynthSolutions(std::map<Node, std::map<Node, Node> >& sol_map);
 129   /**
 130    * The feasible guard whose semantics are "this conjecture is feasiable".
 131    * This is "G" in Figure 3 of Reynolds et al CAV 2015.
 132    */
 133   Node getGuard() const;
 134   /** is ground */
 135   bool isGround() { return d_inner_vars.empty(); }
 136   /** are we using single invocation techniques */
 137   bool isSingleInvocation() const;
 138   /** preregister conjecture
 139    * This is used as a heuristic for solution reconstruction, so that we
 140    * remember expressions in the conjecture before preprocessing, since they
 141    * may be helpful during solution reconstruction (Figure 5 of Reynolds et al
 142    * CAV 2015)
 143    */
 144   void preregisterConjecture(Node q);
 145   /** assign conjecture q to this class */
 146   void assign(Node q);
 147   /** has a conjecture been assigned to this class */
 148   bool isAssigned() { return !d_embed_quant.isNull(); }
 149   /**
 150    * Get model value for term n.
 151    */
 152   Node getModelValue(Node n);
 153
 154   /** get utility for static preprocessing and analysis of conjectures */
 155   SynthConjectureProcess* getProcess() { return d_ceg_proc.get(); }
 156   /** get constant repair utility */
 157   SygusRepairConst* getRepairConst() { return d_sygus_rconst.get(); }
 158   /** get program by examples module */
 159   SygusPbe* getPbe() { return d_ceg_pbe.get(); }
 160   /** get the symmetry breaking predicate for type */
 161   Node getSymmetryBreakingPredicate(
 162       Node x, Node e, TypeNode tn, unsigned tindex, unsigned depth);
 163   /** print out debug information about this conjecture */
 164   void debugPrint(const char* c);
 165   /** check side condition
 166    *
 167    * This returns false if the solution { d_candidates -> cvals } does not
 168    * satisfy the side condition of the conjecture maintained by this class,
 169    * if it exists, and true otherwise.
 170    */
 171   bool checkSideCondition(const std::vector<Node>& cvals) const;
 172
 173  private:
 174   /** reference to quantifier engine */
 175   QuantifiersEngine* d_qe;
 176   /** pointer to the synth engine that owns this */
 177   SynthEngine* d_parent;
 178   /** reference to the statistics of parent */
 179   SygusStatistics& d_stats;
 180   /** term database sygus of d_qe */
 181   TermDbSygus* d_tds;
 182   /** The feasible guard. */
 183   Node d_feasible_guard;
 184   /**
 185    * Do we have a solution in this solve context? This flag is reset to false
 186    * on every call to presolve.
 187    */
 188   bool d_hasSolution;
 189   /** the decision strategy for the feasible guard */
 190   std::unique_ptr<DecisionStrategy> d_feasible_strategy;
 191   /** single invocation utility */
 192   std::unique_ptr<CegSingleInv> d_ceg_si;
 193   /** utility for static preprocessing and analysis of conjectures */
 194   std::unique_ptr<SynthConjectureProcess> d_ceg_proc;
 195   /** grammar utility */
 196   std::unique_ptr<CegGrammarConstructor> d_ceg_gc;
 197   /** repair constant utility */
 198   std::unique_ptr<SygusRepairConst> d_sygus_rconst;
 199   /** connective core utility */
 200   std::unique_ptr<CegisCoreConnective> d_sygus_ccore;
 201
 202   //------------------------modules
 203   /** program by examples module */
 204   std::unique_ptr<SygusPbe> d_ceg_pbe;
 205   /** CEGIS module */
 206   std::unique_ptr<Cegis> d_ceg_cegis;
 207   /** CEGIS UNIF module */
 208   std::unique_ptr<CegisUnif> d_ceg_cegisUnif;
 209   /** the set of active modules (subset of the above list) */
 210   std::vector<SygusModule*> d_modules;
 211   /** master module
 212    *
 213    * This is the module (one of those above) that takes sole responsibility
 214    * for this conjecture, determined during assign(...).
 215    */
 216   SygusModule* d_master;
 217   //------------------------end modules
 218
 219   //------------------------enumerators
 220   /**
 221    * Get model values for terms n, store in vector v. This method returns true
 222    * if and only if all values added to v are non-null.
 223    *
 224    * The argument activeIncomplete indicates whether n contains an active
 225    * enumerator that is currently not finished enumerating values, but returned
 226    * null on a call to getEnumeratedValue. This value is used for determining
 227    * whether we should call getEnumeratedValues again within a call to
 228    * SynthConjecture::check.
 229    *
 230    * It removes terms from n that correspond to "inactive" enumerators, that
 231    * is, enumerators whose values have been exhausted.
 232    */
 233   bool getEnumeratedValues(std::vector<Node>& n,
 234                            std::vector<Node>& v,
 235                            bool& activeIncomplete);
 236   /**
 237    * Get model value for term n. If n has a value that was excluded by
 238    * datatypes sygus symmetry breaking, this method returns null. It sets
 239    * activeIncomplete to true if there is an actively-generated enumerator whose
 240    * current value is null but it has not finished generating values.
 241    */
 242   Node getEnumeratedValue(Node n, bool& activeIncomplete);
 243   /** enumerator generators for each actively-generated enumerator */
 244   std::map<Node, std::unique_ptr<EnumValGenerator> > d_evg;
 245   /**
 246    * Map from enumerators to whether they are currently being
 247    * "actively-generated". That is, we are in a state where we have called
 248    * d_evg[e].addValue(v) for some v, and d_evg[e].getNext() has not yet
 249    * returned null. The range of this map stores the abstract value that
 250    * we are currently generating values from.
 251    */
 252   std::map<Node, Node> d_ev_curr_active_gen;
 253   /** the current waiting value of each actively-generated enumerator, if any
 254    *
 255    * This caches values that are actively generated and that we have not yet
 256    * passed to a call to SygusModule::constructCandidates. An example of when
 257    * this may occur is when there are two actively-generated enumerators e1 and
 258    * e2. Say on some iteration we actively-generate v1 for e1, the value
 259    * of e2 was excluded by symmetry breaking, and say the current master sygus
 260    * module does not handle partial models. Hence, we abort the current check.
 261    * We remember that the value of e1 was v1 by storing it here, so that on
 262    * a future check when v2 has a proper value, it is returned.
 263    */
 264   std::map<Node, Node> d_ev_active_gen_waiting;
 265   /** the first value enumerated for each actively-generated enumerator
 266    *
 267    * This is to implement an optimization that only guards the blocking lemma
 268    * for the first value of an actively-generated enumerator.
 269    */
 270   std::map<Node, Node> d_ev_active_gen_first_val;
 271   //------------------------end enumerators
 272
 273   /** list of constants for quantified formula
 274    * The outer Skolems for the negation of d_embed_quant.
 275    */
 276   std::vector<Node> d_candidates;
 277   /** base instantiation
 278    * If d_embed_quant is forall d. exists y. P( d, y ), then
 279    * this is the formula  exists y. P( d_candidates, y ). Notice that
 280    * (exists y. F) is shorthand above for ~( forall y. ~F ).
 281    */
 282   Node d_base_inst;
 283   /** list of variables on inner quantification */
 284   std::vector<Node> d_inner_vars;
 285   /**
 286    * The set of skolems for the current "verification" lemma, if one exists.
 287    * This may be added to during calls to doCheck(). The model values for these
 288    * skolems are analyzed during doRefine().
 289    */
 290   std::vector<Node> d_ce_sk_vars;
 291   /**
 292    * If we have already tested the satisfiability of the current verification
 293    * lemma, this stores the model values of d_ce_sk_vars in the current
 294    * (satisfiable, failed) verification lemma.
 295    */
 296   std::vector<Node> d_ce_sk_var_mvs;
 297   /**
 298    * Whether the above vector has been set. We have this flag since the above
 299    * vector may be set to empty (e.g. for ground synthesis conjectures).
 300    */
 301   bool d_set_ce_sk_vars;
 302
 303   /** the asserted (negated) conjecture */
 304   Node d_quant;
 305   /**
 306    * The side condition for solving the conjecture, after conversion to deep
 307    * embedding.
 308    */
 309   Node d_embedSideCondition;
 310   /** (negated) conjecture after simplification */
 311   Node d_simp_quant;
 312   /** (negated) conjecture after simplification, conversion to deep embedding */
 313   Node d_embed_quant;
 314   /** candidate information */
 315   class CandidateInfo
 316   {
 317    public:
 318     CandidateInfo() {}
 319     /** list of terms we have instantiated candidates with */
 320     std::vector<Node> d_inst;
 321   };
 322   std::map<Node, CandidateInfo> d_cinfo;
 323   /**
 324    * The first index of an instantiation in CandidateInfo::d_inst that we have
 325    * not yet tried to repair.
 326    */
 327   unsigned d_repair_index;
 328   /** number of times we have called doRefine */
 329   unsigned d_refine_count;
 330   /** get candidadate */
 331   Node getCandidate(unsigned int i) { return d_candidates[i]; }
 332   /** record instantiation (this is used to construct solutions later) */
 333   void recordInstantiation(std::vector<Node>& vs)
 334   {
 335     Assert(vs.size() == d_candidates.size());
 336     for (unsigned i = 0; i < vs.size(); i++)
 337     {
 338       d_cinfo[d_candidates[i]].d_inst.push_back(vs[i]);
 339     }
 340   }
 341   /** get synth solutions internal
 342    *
 343    * This function constructs the body of solutions for all
 344    * functions-to-synthesize in this conjecture and stores them in sols, in
 345    * order. For each solution added to sols, we add an integer indicating what
 346    * kind of solution n is, where if sols[i] = n, then
 347    *   if status[i] = 0: n is the (builtin term) corresponding to the solution,
 348    *   if status[i] = 1: n is the sygus representation of the solution.
 349    * We store builtin versions under some conditions (such as when the sygus
 350    * grammar is being ignored).
 351    *
 352    * This consults the single invocation module to get synthesis solutions if
 353    * isSingleInvocation() returns true.
 354    *
 355    * For example, for conjecture exists fg. forall x. f(x)>g(x), this function
 356    * may set ( sols, status ) to ( { x+1, d_x() }, { 1, 0 } ), where d_x() is
 357    * the sygus datatype constructor corresponding to variable x.
 358    */
 359   bool getSynthSolutionsInternal(std::vector<Node>& sols,
 360                                  std::vector<int>& status);
 361   //-------------------------------- sygus stream
 362   /** current stream guard */
 363   Node d_current_stream_guard;
 364   /** the decision strategy for streaming solutions */
 365   class SygusStreamDecisionStrategy : public DecisionStrategyFmf
 366   {
 367    public:
 368     SygusStreamDecisionStrategy(context::Context* satContext,
 369                                 Valuation valuation);
 370     /** make literal */
 371     Node mkLiteral(unsigned i) override;
 372     /** identify */
 373     std::string identify() const override
 374     {
 375       return std::string("sygus_stream");
 376     }
 377   };
 378   std::unique_ptr<SygusStreamDecisionStrategy> d_stream_strategy;
 379   /** get current stream guard */
 380   Node getCurrentStreamGuard() const;
 381   /** get stream guarded lemma
 382    *
 383    * If sygusStream is enabled, this returns ( G V n ) where G is the guard
 384    * returned by getCurrentStreamGuard, otherwise this returns n.
 385    */
 386   Node getStreamGuardedLemma(Node n) const;
 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