Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- DeltaAlgorithm.h - A Set Minimization Algorithm ---------*- C++ -*--===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_DELTAALGORITHM_H

#define LLVM_ADT_DELTAALGORITHM_H

#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 {

public:

  using change_ty = unsigned;

  // FIXME: Use a decent data structure.

  using changeset_ty = std::set<change_ty>;

  using changesetlist_ty = std::vector<changeset_ty>;

private:

  /// 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 partitioned 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);

protected:

  /// 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;

public:

  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

#endif // LLVM_ADT_DELTAALGORITHM_H