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79 lines
3.1 KiB
C++
79 lines
3.1 KiB
C++
//===- DAGDeltaAlgorithm.h - A DAG Minimization Algorithm ------*- C++ -*--===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_DAGDELTAALGORITHM_H
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#define LLVM_ADT_DAGDELTAALGORITHM_H
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#include <set>
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#include <utility>
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#include <vector>
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namespace llvm {
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/// DAGDeltaAlgorithm - Implements a "delta debugging" algorithm for minimizing
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/// directed acyclic graphs using a predicate function.
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///
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/// The result of the algorithm is a subset of the input change set which is
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/// guaranteed to satisfy the predicate, assuming that the input set did. For
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/// well formed predicates, the result set is guaranteed to be such that
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/// removing any single element not required by the dependencies on the other
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/// elements would falsify the predicate.
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///
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/// The DAG should be used to represent dependencies in the changes which are
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/// likely to hold across the predicate function. That is, for a particular
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/// changeset S and predicate P:
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///
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/// P(S) => P(S union pred(S))
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///
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/// The minimization algorithm uses this dependency information to attempt to
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/// eagerly prune large subsets of changes. As with \see DeltaAlgorithm, the DAG
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/// is not required to satisfy this property, but the algorithm will run
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/// substantially fewer tests with appropriate dependencies. \see DeltaAlgorithm
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/// for more information on the properties which the predicate function itself
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/// should satisfy.
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class DAGDeltaAlgorithm {
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virtual void anchor();
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public:
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using change_ty = unsigned;
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using edge_ty = std::pair<change_ty, change_ty>;
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// FIXME: Use a decent data structure.
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using changeset_ty = std::set<change_ty>;
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using changesetlist_ty = std::vector<changeset_ty>;
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public:
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virtual ~DAGDeltaAlgorithm() = default;
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/// Run - Minimize the DAG formed by the \p Changes vertices and the
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/// \p Dependencies edges by executing \see ExecuteOneTest() on subsets of
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/// changes and returning the smallest set which still satisfies the test
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/// predicate and the input \p Dependencies.
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///
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/// \param Changes The list of changes.
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///
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/// \param Dependencies The list of dependencies amongst changes. For each
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/// (x,y) in \p Dependencies, both x and y must be in \p Changes. The
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/// minimization algorithm guarantees that for each tested changed set S,
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/// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic
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/// dependencies.
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changeset_ty Run(const changeset_ty &Changes,
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const std::vector<edge_ty> &Dependencies);
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/// UpdatedSearchState - Callback used when the search state changes.
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virtual void UpdatedSearchState(const changeset_ty &Changes,
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const changesetlist_ty &Sets,
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const changeset_ty &Required) {}
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/// ExecuteOneTest - Execute a single test predicate on the change set \p S.
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virtual bool ExecuteOneTest(const changeset_ty &S) = 0;
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};
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} // end namespace llvm
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#endif // LLVM_ADT_DAGDELTAALGORITHM_H
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