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 <set>
13 #include <vector>
14 
15 namespace 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.
38 class DAGDeltaAlgorithm {
39   virtual void anchor();
40 public:
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 
48 public:
~DAGDeltaAlgorithm()49   virtual ~DAGDeltaAlgorithm() {}
50 
51   /// Run - Minimize the DAG formed by the \p Changes vertices and the
52   /// \p 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 \p 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 \p Dependencies, both x and y must be in \p Changes. The
60   /// minimization algorithm guarantees that for each tested changed set S,
61   /// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic
62   /// dependencies.
63   changeset_ty Run(const changeset_ty &Changes,
64                    const std::vector<edge_ty> &Dependencies);
65 
66   /// UpdatedSearchState - Callback used when the search state changes.
UpdatedSearchState(const changeset_ty & Changes,const changesetlist_ty & Sets,const changeset_ty & Required)67   virtual void UpdatedSearchState(const changeset_ty &Changes,
68                                   const changesetlist_ty &Sets,
69                                   const changeset_ty &Required) {}
70 
71   /// ExecuteOneTest - Execute a single test predicate on the change set \p S.
72   virtual bool ExecuteOneTest(const changeset_ty &S) = 0;
73 };
74 
75 } // end namespace llvm
76 
77 #endif
78