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93 lines
3.5 KiB
C++
93 lines
3.5 KiB
C++
//===- DeltaAlgorithm.h - A Set 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_DELTAALGORITHM_H
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#define LLVM_ADT_DELTAALGORITHM_H
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#include <set>
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#include <vector>
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namespace llvm {
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/// DeltaAlgorithm - Implements the delta debugging algorithm (A. Zeller '99)
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/// for minimizing arbitrary sets 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 would falsify the predicate.
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///
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/// For best results the predicate function *should* (but need not) satisfy
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/// certain properties, in particular:
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/// (1) The predicate should return false on an empty set and true on the full
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/// set.
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/// (2) If the predicate returns true for a set of changes, it should return
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/// true for all supersets of that set.
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///
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/// It is not an error to provide a predicate that does not satisfy these
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/// requirements, and the algorithm will generally produce reasonable
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/// results. However, it may run substantially more tests than with a good
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/// predicate.
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class DeltaAlgorithm {
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public:
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using change_ty = unsigned;
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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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private:
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/// Cache of failed test results. Successful test results are never cached
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/// since we always reduce following a success.
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std::set<changeset_ty> FailedTestsCache;
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/// GetTestResult - Get the test result for the \p Changes from the
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/// cache, executing the test if necessary.
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///
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/// \param Changes - The change set to test.
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/// \return - The test result.
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bool GetTestResult(const changeset_ty &Changes);
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/// Split - Partition a set of changes \p S into one or two subsets.
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void Split(const changeset_ty &S, changesetlist_ty &Res);
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/// Delta - Minimize a set of \p Changes which has been partioned into
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/// smaller sets, by attempting to remove individual subsets.
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changeset_ty Delta(const changeset_ty &Changes,
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const changesetlist_ty &Sets);
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/// Search - Search for a subset (or subsets) in \p Sets which can be
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/// removed from \p Changes while still satisfying the predicate.
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///
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/// \param Res - On success, a subset of Changes which satisfies the
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/// predicate.
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/// \return - True on success.
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bool Search(const changeset_ty &Changes, const changesetlist_ty &Sets,
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changeset_ty &Res);
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protected:
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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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/// 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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DeltaAlgorithm& operator=(const DeltaAlgorithm&) = default;
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public:
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virtual ~DeltaAlgorithm();
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/// Run - Minimize the set \p Changes by executing \see ExecuteOneTest() on
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/// subsets of changes and returning the smallest set which still satisfies
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/// the test predicate.
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changeset_ty Run(const changeset_ty &Changes);
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};
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} // end namespace llvm
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#endif // LLVM_ADT_DELTAALGORITHM_H
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