• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 <vector>
13 #include <set>
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   typedef unsigned change_ty;
39   // FIXME: Use a decent data structure.
40   typedef std::set<change_ty> changeset_ty;
41   typedef std::vector<changeset_ty> changesetlist_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 \arg 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 \arg S into one or two subsets.
56   void Split(const changeset_ty &S, changesetlist_ty &Res);
57 
58   /// Delta - Minimize a set of \arg 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 \arg Sets which can be
64   /// removed from \arg 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.
UpdatedSearchState(const changeset_ty & Changes,const changesetlist_ty & Sets)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 \arg S.
78   virtual bool ExecuteOneTest(const changeset_ty &S) = 0;
79 
80 public:
81   virtual ~DeltaAlgorithm();
82 
83   /// Run - Minimize the set \arg Changes by executing \see ExecuteOneTest() on
84   /// subsets of changes and returning the smallest set which still satisfies
85   /// the test predicate.
86   changeset_ty Run(const changeset_ty &Changes);
87 };
88 
89 } // end namespace llvm
90 
91 #endif
92