1 //===- DAGDeltaAlgorithm.h - A DAG Minimization Algorithm ------*- C++ -*--===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //===----------------------------------------------------------------------===//
9 #ifndef LLVM_ADT_DAGDELTAALGORITHM_H
10 #define LLVM_ADT_DAGDELTAALGORITHM_H
18 /// DAGDeltaAlgorithm - Implements a "delta debugging" algorithm for minimizing
19 /// directed acyclic graphs using a predicate function.
21 /// The result of the algorithm is a subset of the input change set which is
22 /// guaranteed to satisfy the predicate, assuming that the input set did. For
23 /// well formed predicates, the result set is guaranteed to be such that
24 /// removing any single element not required by the dependencies on the other
25 /// elements would falsify the predicate.
27 /// The DAG should be used to represent dependencies in the changes which are
28 /// likely to hold across the predicate function. That is, for a particular
29 /// changeset S and predicate P:
31 /// P(S) => P(S union pred(S))
33 /// The minization algorithm uses this dependency information to attempt to
34 /// eagerly prune large subsets of changes. As with \see DeltaAlgorithm, the DAG
35 /// is not required to satisfy this property, but the algorithm will run
36 /// substantially fewer tests with appropriate dependencies. \see DeltaAlgorithm
37 /// for more information on the properties which the predicate function itself
39 class DAGDeltaAlgorithm {
40 virtual void anchor();
43 using change_ty = unsigned;
44 using edge_ty = std::pair<change_ty, change_ty>;
46 // FIXME: Use a decent data structure.
47 using changeset_ty = std::set<change_ty>;
48 using changesetlist_ty = std::vector<changeset_ty>;
51 virtual ~DAGDeltaAlgorithm() = default;
53 /// Run - Minimize the DAG formed by the \p Changes vertices and the
54 /// \p Dependencies edges by executing \see ExecuteOneTest() on subsets of
55 /// changes and returning the smallest set which still satisfies the test
56 /// predicate and the input \p Dependencies.
58 /// \param Changes The list of changes.
60 /// \param Dependencies The list of dependencies amongst changes. For each
61 /// (x,y) in \p Dependencies, both x and y must be in \p Changes. The
62 /// minimization algorithm guarantees that for each tested changed set S,
63 /// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic
65 changeset_ty Run(const changeset_ty &Changes,
66 const std::vector<edge_ty> &Dependencies);
68 /// UpdatedSearchState - Callback used when the search state changes.
69 virtual void UpdatedSearchState(const changeset_ty &Changes,
70 const changesetlist_ty &Sets,
71 const changeset_ty &Required) {}
73 /// ExecuteOneTest - Execute a single test predicate on the change set \p S.
74 virtual bool ExecuteOneTest(const changeset_ty &S) = 0;
77 } // end namespace llvm
79 #endif // LLVM_ADT_DAGDELTAALGORITHM_H