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/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
  37 namespace CVC4 {
  38 namespace theory {
  39 namespace quantifiers {
  40
  41 class SynthEngine;
  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   virtual bool increment() = 0;
  64   /** Get the current concrete value generated by this class. */
  65   virtual Node getCurrent() = 0;
  66 };
  67
  68 /** a synthesis conjecture
  69  * This class implements approaches for a synthesis conecjture, given by data
  70  * member d_quant.
  71  * This includes both approaches for synthesis in Reynolds et al CAV 2015. It
  72  * determines which approach and optimizations are applicable to the
  73  * conjecture, and has interfaces for implementing them.
  74  */
  75 class SynthConjecture
  76 {
  77  public:
  78   SynthConjecture(QuantifiersEngine* qe, SynthEngine* p, SygusStatistics& s);
  79   ~SynthConjecture();
  80   /** presolve */
  81   void presolve();
  82   /** get original version of conjecture */
  83   Node getConjecture() { return d_quant; }
  84   /** get deep embedding version of conjecture */
  85   Node getEmbeddedConjecture() { return d_embed_quant; }
  86   //-------------------------------for counterexample-guided check/refine
  87   /** increment the number of times we have successfully done candidate
  88    * refinement */
  89   void incrementRefineCount() { d_refine_count++; }
  90   /** whether the conjecture is waiting for a call to doCheck below */
  91   bool needsCheck();
  92   /** whether the conjecture is waiting for a call to doRefine below */
  93   bool needsRefinement() const;
  94   /** do syntax-guided enumerative check
  95    *
  96    * This is step 2(a) of Figure 3 of Reynolds et al CAV 2015.
  97    *
  98    * The method returns true if this conjecture is finished trying solutions
  99    * for the given call to SynthEngine::check.
 100    *
 101    * Notice that we make multiple calls to doCheck on one call to
 102    * SynthEngine::check. For example, if we are using an actively-generated
 103    * enumerator, one enumerated (abstract) term may correspond to multiple
 104    * concrete terms t1, ..., tn to check, where we make up to n calls to doCheck
 105    * when each of t1, ..., tn fails to satisfy the current refinement lemmas.
 106    */
 107   bool doCheck(std::vector<Node>& lems);
 108   /** do refinement
 109    * This is step 2(b) of Figure 3 of Reynolds et al CAV 2015.
 110    */
 111   void doRefine(std::vector<Node>& lems);
 112   //-------------------------------end for counterexample-guided check/refine
 113   /**
 114    * Prints the synthesis solution to output stream out. This invokes solution
 115    * reconstruction if the conjecture is single invocation. Otherwise, it
 116    * returns the solution found by sygus enumeration.
 117    */
 118   void printSynthSolution(std::ostream& out);
 119   /** get synth solutions
 120    *
 121    * This method returns true if this class has a solution available to the
 122    * conjecture that it was assigned.
 123    *
 124    * Let q be the synthesis conjecture assigned to this class.
 125    * This method adds entries to sol_map[q] that map functions-to-synthesize to
 126    * their builtin solution, which has the same type. For example, for synthesis
 127    * conjecture exists f. forall x. f( x )>x, this function will update
 128    * sol_map[q] to contain the entry:
 129    *   f -> (lambda x. x+1)
 130    */
 131   bool getSynthSolutions(std::map<Node, std::map<Node, Node> >& sol_map);
 132   /**
 133    * The feasible guard whose semantics are "this conjecture is feasiable".
 134    * This is "G" in Figure 3 of Reynolds et al CAV 2015.
 135    */
 136   Node getGuard() const;
 137   /** is ground */
 138   bool isGround() { return d_inner_vars.empty(); }
 139   /** are we using single invocation techniques */
 140   bool isSingleInvocation() const;
 141   /** preregister conjecture
 142    * This is used as a heuristic for solution reconstruction, so that we
 143    * remember expressions in the conjecture before preprocessing, since they
 144    * may be helpful during solution reconstruction (Figure 5 of Reynolds et al
 145    * CAV 2015)
 146    */
 147   void preregisterConjecture(Node q);
 148   /** assign conjecture q to this class */
 149   void assign(Node q);
 150   /** has a conjecture been assigned to this class */
 151   bool isAssigned() { return !d_embed_quant.isNull(); }
 152   /**
 153    * Get model value for term n.
 154    */
 155   Node getModelValue(Node n);
 156
 157   /** get utility for static preprocessing and analysis of conjectures */
 158   SynthConjectureProcess* getProcess() { return d_ceg_proc.get(); }
 159   /** get constant repair utility */
 160   SygusRepairConst* getRepairConst() { return d_sygus_rconst.get(); }
 161   /** get example inference utility */
 162   ExampleInfer* getExampleInfer() { return d_exampleInfer.get(); }
 163   /** get the example evaluation cache utility for enumerator e */
 164   ExampleEvalCache* getExampleEvalCache(Node e);
 165   /** get program by examples module */
 166   SygusPbe* getPbe() { return d_ceg_pbe.get(); }
 167   /** get the symmetry breaking predicate for type */
 168   Node getSymmetryBreakingPredicate(
 169       Node x, Node e, TypeNode tn, unsigned tindex, unsigned depth);
 170   /** print out debug information about this conjecture */
 171   void debugPrint(const char* c);
 172   /** check side condition
 173    *
 174    * This returns false if the solution { d_candidates -> cvals } does not
 175    * satisfy the side condition of the conjecture maintained by this class,
 176    * if it exists, and true otherwise.
 177    */
 178   bool checkSideCondition(const std::vector<Node>& cvals) const;
 179
 180  private:
 181   /** reference to quantifier engine */
 182   QuantifiersEngine* d_qe;
 183   /** pointer to the synth engine that owns this */
 184   SynthEngine* d_parent;
 185   /** reference to the statistics of parent */
 186   SygusStatistics& d_stats;
 187   /** term database sygus of d_qe */
 188   TermDbSygus* d_tds;
 189   /** The feasible guard. */
 190   Node d_feasible_guard;
 191   /**
 192    * Do we have a solution in this solve context? This flag is reset to false
 193    * on every call to presolve.
 194    */
 195   bool d_hasSolution;
 196   /** the decision strategy for the feasible guard */
 197   std::unique_ptr<DecisionStrategy> d_feasible_strategy;
 198   /** single invocation utility */
 199   std::unique_ptr<CegSingleInv> d_ceg_si;
 200   /** utility for static preprocessing and analysis of conjectures */
 201   std::unique_ptr<SynthConjectureProcess> d_ceg_proc;
 202   /** grammar utility */
 203   std::unique_ptr<CegGrammarConstructor> d_ceg_gc;
 204   /** repair constant utility */
 205   std::unique_ptr<SygusRepairConst> d_sygus_rconst;
 206   /** example inference utility */
 207   std::unique_ptr<ExampleInfer> d_exampleInfer;
 208   /** example evaluation cache utility for each enumerator */
 209   std::map<Node, std::unique_ptr<ExampleEvalCache> > d_exampleEvalCache;
 210
 211   //------------------------modules
 212   /** program by examples module */
 213   std::unique_ptr<SygusPbe> d_ceg_pbe;
 214   /** CEGIS module */
 215   std::unique_ptr<Cegis> d_ceg_cegis;
 216   /** CEGIS UNIF module */
 217   std::unique_ptr<CegisUnif> d_ceg_cegisUnif;
 218   /** connective core utility */
 219   std::unique_ptr<CegisCoreConnective> d_sygus_ccore;
 220   /** the set of active modules (subset of the above list) */
 221   std::vector<SygusModule*> d_modules;
 222   /** master module
 223    *
 224    * This is the module (one of those above) that takes sole responsibility
 225    * for this conjecture, determined during assign(...).
 226    */
 227   SygusModule* d_master;
 228   //------------------------end modules
 229
 230   //------------------------enumerators
 231   /**
 232    * Get model values for terms n, store in vector v. This method returns true
 233    * if and only if all values added to v are non-null.
 234    *
 235    * The argument activeIncomplete indicates whether n contains an active
 236    * enumerator that is currently not finished enumerating values, but returned
 237    * null on a call to getEnumeratedValue. This value is used for determining
 238    * whether we should call getEnumeratedValues again within a call to
 239    * SynthConjecture::check.
 240    *
 241    * It removes terms from n that correspond to "inactive" enumerators, that
 242    * is, enumerators whose values have been exhausted.
 243    */
 244   bool getEnumeratedValues(std::vector<Node>& n,
 245                            std::vector<Node>& v,
 246                            bool& activeIncomplete);
 247   /**
 248    * Get model value for term n. If n has a value that was excluded by
 249    * datatypes sygus symmetry breaking, this method returns null. It sets
 250    * activeIncomplete to true if there is an actively-generated enumerator whose
 251    * current value is null but it has not finished generating values.
 252    */
 253   Node getEnumeratedValue(Node n, bool& activeIncomplete);
 254   /** enumerator generators for each actively-generated enumerator */
 255   std::map<Node, std::unique_ptr<EnumValGenerator> > d_evg;
 256   /**
 257    * Map from enumerators to whether they are currently being
 258    * "actively-generated". That is, we are in a state where we have called
 259    * d_evg[e].addValue(v) for some v, and d_evg[e].getNext() has not yet
 260    * returned null. The range of this map stores the abstract value that
 261    * we are currently generating values from.
 262    */
 263   std::map<Node, Node> d_ev_curr_active_gen;
 264   /** the current waiting value of each actively-generated enumerator, if any
 265    *
 266    * This caches values that are actively generated and that we have not yet
 267    * passed to a call to SygusModule::constructCandidates. An example of when
 268    * this may occur is when there are two actively-generated enumerators e1 and
 269    * e2. Say on some iteration we actively-generate v1 for e1, the value
 270    * of e2 was excluded by symmetry breaking, and say the current master sygus
 271    * module does not handle partial models. Hence, we abort the current check.
 272    * We remember that the value of e1 was v1 by storing it here, so that on
 273    * a future check when v2 has a proper value, it is returned.
 274    */
 275   std::map<Node, Node> d_ev_active_gen_waiting;
 276   /** the first value enumerated for each actively-generated enumerator
 277    *
 278    * This is to implement an optimization that only guards the blocking lemma
 279    * for the first value of an actively-generated enumerator.
 280    */
 281   std::map<Node, Node> d_ev_active_gen_first_val;
 282   //------------------------end enumerators
 283
 284   /** list of constants for quantified formula
 285    * The outer Skolems for the negation of d_embed_quant.
 286    */
 287   std::vector<Node> d_candidates;
 288   /** base instantiation
 289    * If d_embed_quant is forall d. exists y. P( d, y ), then
 290    * this is the formula  exists y. P( d_candidates, y ). Notice that
 291    * (exists y. F) is shorthand above for ~( forall y. ~F ).
 292    */
 293   Node d_base_inst;
 294   /** list of variables on inner quantification */
 295   std::vector<Node> d_inner_vars;
 296   /**
 297    * The set of skolems for the current "verification" lemma, if one exists.
 298    * This may be added to during calls to doCheck(). The model values for these
 299    * skolems are analyzed during doRefine().
 300    */
 301   std::vector<Node> d_ce_sk_vars;
 302   /**
 303    * If we have already tested the satisfiability of the current verification
 304    * lemma, this stores the model values of d_ce_sk_vars in the current
 305    * (satisfiable, failed) verification lemma.
 306    */
 307   std::vector<Node> d_ce_sk_var_mvs;
 308   /**
 309    * Whether the above vector has been set. We have this flag since the above
 310    * vector may be set to empty (e.g. for ground synthesis conjectures).
 311    */
 312   bool d_set_ce_sk_vars;
 313
 314   /** the asserted (negated) conjecture */
 315   Node d_quant;
 316   /**
 317    * The side condition for solving the conjecture, after conversion to deep
 318    * embedding.
 319    */
 320   Node d_embedSideCondition;
 321   /** (negated) conjecture after simplification */
 322   Node d_simp_quant;
 323   /** (negated) conjecture after simplification, conversion to deep embedding */
 324   Node d_embed_quant;
 325   /** candidate information */
 326   class CandidateInfo
 327   {
 328    public:
 329     CandidateInfo() {}
 330     /** list of terms we have instantiated candidates with */
 331     std::vector<Node> d_inst;
 332   };
 333   std::map<Node, CandidateInfo> d_cinfo;
 334   /**
 335    * The first index of an instantiation in CandidateInfo::d_inst that we have
 336    * not yet tried to repair.
 337    */
 338   unsigned d_repair_index;
 339   /** number of times we have called doRefine */
 340   unsigned d_refine_count;
 341   /** get candidadate */
 342   Node getCandidate(unsigned int i) { return d_candidates[i]; }
 343   /** record instantiation (this is used to construct solutions later) */
 344   void recordInstantiation(std::vector<Node>& vs)
 345   {
 346     Assert(vs.size() == d_candidates.size());
 347     for (unsigned i = 0; i < vs.size(); i++)
 348     {
 349       d_cinfo[d_candidates[i]].d_inst.push_back(vs[i]);
 350     }
 351   }
 352   /** get synth solutions internal
 353    *
 354    * This function constructs the body of solutions for all
 355    * functions-to-synthesize in this conjecture and stores them in sols, in
 356    * order. For each solution added to sols, we add an integer indicating what
 357    * kind of solution n is, where if sols[i] = n, then
 358    *   if status[i] = 0: n is the (builtin term) corresponding to the solution,
 359    *   if status[i] = 1: n is the sygus representation of the solution.
 360    * We store builtin versions under some conditions (such as when the sygus
 361    * grammar is being ignored).
 362    *
 363    * This consults the single invocation module to get synthesis solutions if
 364    * isSingleInvocation() returns true.
 365    *
 366    * For example, for conjecture exists fg. forall x. f(x)>g(x), this function
 367    * may set ( sols, status ) to ( { x+1, d_x() }, { 1, 0 } ), where d_x() is
 368    * the sygus datatype constructor corresponding to variable x.
 369    */
 370   bool getSynthSolutionsInternal(std::vector<Node>& sols,
 371                                  std::vector<int>& status);
 372   //-------------------------------- sygus stream
 373   /** current stream guard */
 374   Node d_current_stream_guard;
 375   /** the decision strategy for streaming solutions */
 376   class SygusStreamDecisionStrategy : public DecisionStrategyFmf
 377   {
 378    public:
 379     SygusStreamDecisionStrategy(context::Context* satContext,
 380                                 Valuation valuation);
 381     /** make literal */
 382     Node mkLiteral(unsigned i) override;
 383     /** identify */
 384     std::string identify() const override
 385     {
 386       return std::string("sygus_stream");
 387     }
 388   };
 389   std::unique_ptr<SygusStreamDecisionStrategy> d_stream_strategy;
 390   /** get current stream guard */
 391   Node getCurrentStreamGuard() const;
 392   /** get stream guarded lemma
 393    *
 394    * If sygusStream is enabled, this returns ( G V n ) where G is the guard
 395    * returned by getCurrentStreamGuard, otherwise this returns n.
 396    */
 397   Node getStreamGuardedLemma(Node n) const;
 398   /**
 399    * Prints the current synthesis solution to the output stream indicated by
 400    * the Options object, send a lemma blocking the current solution to the
 401    * output channel, which we refer to as a "stream exclusion lemma".
 402    *
 403    * The argument enums is the set of enumerators that comprise the current
 404    * solution, and values is their current values.
 405    */
 406   void printAndContinueStream(const std::vector<Node>& enums,
 407                               const std::vector<Node>& values);
 408   /** exclude the current solution { enums -> values } */
 409   void excludeCurrentSolution(const std::vector<Node>& enums,
 410                               const std::vector<Node>& values);
 411   /**
 412    * Whether we have guarded a stream exclusion lemma when using sygusStream.
 413    * This is an optimization that allows us to guard only the first stream
 414    * exclusion lemma.
 415    */
 416   bool d_guarded_stream_exc;
 417   //-------------------------------- end sygus stream
 418   /** expression miner managers for each function-to-synthesize
 419    *
 420    * Notice that for each function-to-synthesize, we enumerate a stream of
 421    * candidate solutions, where each of these streams is independent. Thus,
 422    * we maintain separate expression miner managers for each of them.
 423    *
 424    * This is used for the sygusRewSynth() option to synthesize new candidate
 425    * rewrite rules.
 426    */
 427   std::map<Node, ExpressionMinerManager> d_exprm;
 428 };
 429
 430 }  // namespace quantifiers
 431 }  // namespace theory
 432 } /* namespace CVC4 */
 433
 434 #endif