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kpeter (Peter Kovacs)
kpeter@inf.elte.hu
Support tolerance technique for BellmanFord (#51) A new operation traits class BellmanFordToleranceOperationTraits is introduced, which uses the tolerance technique in its less() function. This class can be used with the SetOperationTraits named template parameter.
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2 files changed with 55 insertions and 4 deletions:
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#include <lemon/maps.h>
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#include <lemon/tolerance.h>
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#include <lemon/path.h>
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  /// \brief Default OperationTraits for the BellmanFord algorithm class.
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  /// \brief Default operation traits for the BellmanFord algorithm class.
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  ///  
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  /// value is used as extremal infinity value.
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  ///
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  /// \see BellmanFordToleranceOperationTraits
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  template <
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  struct BellmanFordDefaultOperationTraits {
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    /// \e
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    /// \brief Value type for the algorithm.
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    typedef V Value;
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  /// \brief Operation traits for the BellmanFord algorithm class
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  /// using tolerance.
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  ///
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  /// This operation traits class defines all computational operations
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  /// and constants that are used in the Bellman-Ford algorithm.
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  /// The only difference between this implementation and
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  /// \ref BellmanFordDefaultOperationTraits is that this class uses
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  /// the \ref Tolerance "tolerance technique" in its \ref less()
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  /// function.
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  ///
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  /// \tparam V The value type.
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  /// \tparam eps The epsilon value for the \ref less() function.
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  /// By default, it is the epsilon value used by \ref Tolerance
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  /// "Tolerance<V>".
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  ///
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  /// \see BellmanFordDefaultOperationTraits
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#ifdef DOXYGEN
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  template <typename V, V eps>
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#else
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  template <
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    typename V,
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    V eps = Tolerance<V>::def_epsilon>
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#endif
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  struct BellmanFordToleranceOperationTraits {
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    /// \brief Value type for the algorithm.
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    typedef V Value;
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    /// \brief Gives back the zero value of the type.
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    static Value zero() {
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      return static_cast<Value>(0);
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    }
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    /// \brief Gives back the positive infinity value of the type.
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    static Value infinity() {
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      return std::numeric_limits<Value>::infinity();
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    }
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    /// \brief Gives back the sum of the given two elements.
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    static Value plus(const Value& left, const Value& right) {
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      return left + right;
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    }
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    /// \brief Gives back \c true only if the first value is less than
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    /// the second.
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    static bool less(const Value& left, const Value& right) {
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      return left + eps < right;
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    }
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  };
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  /// \brief Default traits class of BellmanFord class.
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    /// given \c Value type.
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    /// \see BellmanFordDefaultOperationTraits
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    /// \see BellmanFordDefaultOperationTraits,
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    /// BellmanFordToleranceOperationTraits
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    typedef BellmanFordDefaultOperationTraits<Value> OperationTraits;
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    /// given \c Value type.
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    /// \see BellmanFordDefaultOperationTraits
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    /// \see BellmanFordDefaultOperationTraits,
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    /// BellmanFordToleranceOperationTraits
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    typedef BellmanFordDefaultOperationTraits<Value> OperationTraits;
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      ::SetOperationTraits<BellmanFordDefaultOperationTraits<Value> >
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      ::SetOperationTraits<BellmanFordToleranceOperationTraits<Value, 0> >
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      ::Create bf_test(gr,length);
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