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//===- DeltaAlgorithm.h - A Set Minimization Algorithm ---------*- C++ -*--===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include <set>
#include <vector>
namespace llvm {
/// DeltaAlgorithm - Implements the delta debugging algorithm (A. Zeller '99)
/// for minimizing arbitrary sets using a predicate function.
/// The result of the algorithm is a subset of the input change set which is
/// guaranteed to satisfy the predicate, assuming that the input set did. For
/// well formed predicates, the result set is guaranteed to be such that
/// removing any single element would falsify the predicate.
/// For best results the predicate function *should* (but need not) satisfy
/// certain properties, in particular:
/// (1) The predicate should return false on an empty set and true on the full
/// set.
/// (2) If the predicate returns true for a set of changes, it should return
/// true for all supersets of that set.
/// It is not an error to provide a predicate that does not satisfy these
/// requirements, and the algorithm will generally produce reasonable
/// results. However, it may run substantially more tests than with a good
/// predicate.
class DeltaAlgorithm {
using change_ty = unsigned;
// FIXME: Use a decent data structure.
using changeset_ty = std::set<change_ty>;
using changesetlist_ty = std::vector<changeset_ty>;
/// Cache of failed test results. Successful test results are never cached
/// since we always reduce following a success.
std::set<changeset_ty> FailedTestsCache;
/// GetTestResult - Get the test result for the \p Changes from the
/// cache, executing the test if necessary.
/// \param Changes - The change set to test.
/// \return - The test result.
bool GetTestResult(const changeset_ty &Changes);
/// Split - Partition a set of changes \p S into one or two subsets.
void Split(const changeset_ty &S, changesetlist_ty &Res);
/// Delta - Minimize a set of \p Changes which has been partioned into
/// smaller sets, by attempting to remove individual subsets.
changeset_ty Delta(const changeset_ty &Changes,
const changesetlist_ty &Sets);
/// Search - Search for a subset (or subsets) in \p Sets which can be
/// removed from \p Changes while still satisfying the predicate.
/// \param Res - On success, a subset of Changes which satisfies the
/// predicate.
/// \return - True on success.
bool Search(const changeset_ty &Changes, const changesetlist_ty &Sets,
changeset_ty &Res);
/// UpdatedSearchState - Callback used when the search state changes.
virtual void UpdatedSearchState(const changeset_ty &Changes,
const changesetlist_ty &Sets) {}
/// ExecuteOneTest - Execute a single test predicate on the change set \p S.
virtual bool ExecuteOneTest(const changeset_ty &S) = 0;
DeltaAlgorithm& operator=(const DeltaAlgorithm&) = default;
virtual ~DeltaAlgorithm();
/// Run - Minimize the set \p Changes by executing \see ExecuteOneTest() on
/// subsets of changes and returning the smallest set which still satisfies
/// the test predicate.
changeset_ty Run(const changeset_ty &Changes);
} // end namespace llvm