DeltaAlgorithm.h revision c5252da873d547a19069eaf9030fec203f128f66 
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
15namespace 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.
36class DeltaAlgorithm {
37public:
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
43private:
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
72protected:
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
80public:
81  virtual ~DeltaAlgorithm();
82
83  /// Run - Minimize the set \p 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