Andrew Scull | 5e1ddfa | 2018-08-14 10:06:54 +0100 | [diff] [blame] | 1 | //===- DAGDeltaAlgorithm.h - A DAG Minimization Algorithm ------*- C++ -*--===// |
| 2 | // |
Andrew Walbran | 16937d0 | 2019-10-22 13:54:20 +0100 | [diff] [blame^] | 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
Andrew Scull | 5e1ddfa | 2018-08-14 10:06:54 +0100 | [diff] [blame] | 6 | //===----------------------------------------------------------------------===// |
| 7 | |
| 8 | #ifndef LLVM_ADT_DAGDELTAALGORITHM_H |
| 9 | #define LLVM_ADT_DAGDELTAALGORITHM_H |
| 10 | |
| 11 | #include <set> |
| 12 | #include <utility> |
| 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 | |
| 41 | public: |
| 42 | using change_ty = unsigned; |
| 43 | using edge_ty = std::pair<change_ty, change_ty>; |
| 44 | |
| 45 | // FIXME: Use a decent data structure. |
| 46 | using changeset_ty = std::set<change_ty>; |
| 47 | using changesetlist_ty = std::vector<changeset_ty>; |
| 48 | |
| 49 | public: |
| 50 | virtual ~DAGDeltaAlgorithm() = default; |
| 51 | |
| 52 | /// Run - Minimize the DAG formed by the \p Changes vertices and the |
| 53 | /// \p Dependencies edges by executing \see ExecuteOneTest() on subsets of |
| 54 | /// changes and returning the smallest set which still satisfies the test |
| 55 | /// predicate and the input \p Dependencies. |
| 56 | /// |
| 57 | /// \param Changes The list of changes. |
| 58 | /// |
| 59 | /// \param Dependencies The list of dependencies amongst changes. For each |
| 60 | /// (x,y) in \p Dependencies, both x and y must be in \p Changes. The |
| 61 | /// minimization algorithm guarantees that for each tested changed set S, |
| 62 | /// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic |
| 63 | /// dependencies. |
| 64 | changeset_ty Run(const changeset_ty &Changes, |
| 65 | const std::vector<edge_ty> &Dependencies); |
| 66 | |
| 67 | /// UpdatedSearchState - Callback used when the search state changes. |
| 68 | virtual void UpdatedSearchState(const changeset_ty &Changes, |
| 69 | const changesetlist_ty &Sets, |
| 70 | const changeset_ty &Required) {} |
| 71 | |
| 72 | /// ExecuteOneTest - Execute a single test predicate on the change set \p S. |
| 73 | virtual bool ExecuteOneTest(const changeset_ty &S) = 0; |
| 74 | }; |
| 75 | |
| 76 | } // end namespace llvm |
| 77 | |
| 78 | #endif // LLVM_ADT_DAGDELTAALGORITHM_H |