DAGDeltaAlgorithm.h revision 5729c5848c74a2413cc1d32a5f3c746aff5d9ccc 
1//===--- DAGDeltaAlgorithm.h - A DAG 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_DAGDELTAALGORITHM_H
10#define LLVM_ADT_DAGDELTAALGORITHM_H
11
12#include <vector>
13#include <set>
14
15namespace llvm {
16
17/// DAGDeltaAlgorithm - Implements a "delta debugging" algorithm for minimizing
18/// directed acyclic graphs 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 not required by the dependencies on the other
24/// elements would falsify the predicate.
25///
26/// The DAG should be used to represent dependencies in the changes which are
27/// likely to hold across the predicate function. That is, for a particular
28/// changeset S and predicate P:
29///
30///   P(S) => P(S union pred(S))
31///
32/// The minization algorithm uses this dependency information to attempt to
33/// eagerly prune large subsets of changes. As with \see DeltaAlgorithm, the DAG
34/// is not required to satisfy this property, but the algorithm will run
35/// substantially fewer tests with appropriate dependencies. \see DeltaAlgorithm
36/// for more information on the properties which the predicate function itself
37/// should satisfy.
38class DAGDeltaAlgorithm {
39  virtual void anchor();
40public:
41  typedef unsigned change_ty;
42  typedef std::pair<change_ty, change_ty> edge_ty;
43
44  // FIXME: Use a decent data structure.
45  typedef std::set<change_ty> changeset_ty;
46  typedef std::vector<changeset_ty> changesetlist_ty;
47
48public:
49  virtual ~DAGDeltaAlgorithm() {}
50
51  /// Run - Minimize the DAG formed by the \arg Changes vertices and the \arg
52  /// Dependencies edges by executing \see ExecuteOneTest() on subsets of
53  /// changes and returning the smallest set which still satisfies the test
54  /// predicate and the input \arg Dependencies.
55  ///
56  /// \param Changes The list of changes.
57  ///
58  /// \param Dependencies The list of dependencies amongst changes. For each
59  /// (x,y) in \arg Dependencies, both x and y must be in \arg Changes. The
60  /// minimization algorithm guarantees that for each tested changed set S, x
61  /// \in S implies y \in S. It is an error to have cyclic dependencies.
62  changeset_ty Run(const changeset_ty &Changes,
63                   const std::vector<edge_ty> &Dependencies);
64
65  /// UpdatedSearchState - Callback used when the search state changes.
66  virtual void UpdatedSearchState(const changeset_ty &Changes,
67                                  const changesetlist_ty &Sets,
68                                  const changeset_ty &Required) {}
69
70  /// ExecuteOneTest - Execute a single test predicate on the change set \arg S.
71  virtual bool ExecuteOneTest(const changeset_ty &S) = 0;
72};
73
74} // end namespace llvm
75
76#endif
77