1 //===- DeltaAlgorithm.h - A Set Minimization Algorithm ---------*- C++ -*--===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_ADT_DELTAALGORITHM_H 10 #define LLVM_ADT_DELTAALGORITHM_H 11 12 #include <set> 13 #include <vector> 14 15 namespace llvm { 16 17 /// DeltaAlgorithm - Implements the delta debugging algorithm (A. Zeller '99) 18 /// for minimizing arbitrary sets using a predicate function. 19 /// 20 /// The result of the algorithm is a subset of the input change set which is 21 /// guaranteed to satisfy the predicate, assuming that the input set did. For 22 /// well formed predicates, the result set is guaranteed to be such that 23 /// removing any single element would falsify the predicate. 24 /// 25 /// For best results the predicate function *should* (but need not) satisfy 26 /// certain properties, in particular: 27 /// (1) The predicate should return false on an empty set and true on the full 28 /// set. 29 /// (2) If the predicate returns true for a set of changes, it should return 30 /// true for all supersets of that set. 31 /// 32 /// It is not an error to provide a predicate that does not satisfy these 33 /// requirements, and the algorithm will generally produce reasonable 34 /// results. However, it may run substantially more tests than with a good 35 /// predicate. 36 class DeltaAlgorithm { 37 public: 38 using change_ty = unsigned; 39 // FIXME: Use a decent data structure. 40 using changeset_ty = std::set<change_ty>; 41 using changesetlist_ty = std::vector<changeset_ty>; 42 43 private: 44 /// Cache of failed test results. Successful test results are never cached 45 /// since we always reduce following a success. 46 std::set<changeset_ty> FailedTestsCache; 47 48 /// GetTestResult - Get the test result for the \p Changes from the 49 /// cache, executing the test if necessary. 50 /// 51 /// \param Changes - The change set to test. 52 /// \return - The test result. 53 bool GetTestResult(const changeset_ty &Changes); 54 55 /// Split - Partition a set of changes \p S into one or two subsets. 56 void Split(const changeset_ty &S, changesetlist_ty &Res); 57 58 /// Delta - Minimize a set of \p Changes which has been partioned into 59 /// smaller sets, by attempting to remove individual subsets. 60 changeset_ty Delta(const changeset_ty &Changes, 61 const changesetlist_ty &Sets); 62 63 /// Search - Search for a subset (or subsets) in \p Sets which can be 64 /// removed from \p Changes while still satisfying the predicate. 65 /// 66 /// \param Res - On success, a subset of Changes which satisfies the 67 /// predicate. 68 /// \return - True on success. 69 bool Search(const changeset_ty &Changes, const changesetlist_ty &Sets, 70 changeset_ty &Res); 71 72 protected: 73 /// UpdatedSearchState - Callback used when the search state changes. 74 virtual void UpdatedSearchState(const changeset_ty &Changes, 75 const changesetlist_ty &Sets) {} 76 77 /// ExecuteOneTest - Execute a single test predicate on the change set \p S. 78 virtual bool ExecuteOneTest(const changeset_ty &S) = 0; 79 80 DeltaAlgorithm& operator=(const DeltaAlgorithm&) = default; 81 82 public: 83 virtual ~DeltaAlgorithm(); 84 85 /// Run - Minimize the set \p Changes by executing \see ExecuteOneTest() on 86 /// subsets of changes and returning the smallest set which still satisfies 87 /// the test predicate. 88 changeset_ty Run(const changeset_ty &Changes); 89 }; 90 91 } // end namespace llvm 92 93 #endif // LLVM_ADT_DELTAALGORITHM_H 94
