방법: 병렬 작업으로 이진 트리 탐색

다음 예제에서는 병렬 작업을 사용하여 트리 데이터 구조를 트래버스할 수 있는 두 가지 방법을 보여 줍니다. 트리 자체의 생성은 연습으로 남아 있습니다.

예시

public class TreeWalk
{
    static void Main()
    {
        Tree<MyClass> tree = new Tree<MyClass>();

        // ...populate tree (left as an exercise)

        // Define the Action to perform on each node.
        Action<MyClass> myAction = x => Console.WriteLine($"{x.Name} : {x.Number}");

        // Traverse the tree with parallel tasks.
        DoTree(tree, myAction);
    }

    public class MyClass
    {
        public string Name { get; set; }
        public int Number { get; set; }
    }
    public class Tree<T>
    {
        public Tree<T> Left;
        public Tree<T> Right;
        public T Data;
    }

    // By using tasks explicitly.
    public static void DoTree<T>(Tree<T> tree, Action<T> action)
    {
        if (tree == null) return;
        var left = Task.Factory.StartNew(() => DoTree(tree.Left, action));
        var right = Task.Factory.StartNew(() => DoTree(tree.Right, action));
        action(tree.Data);

        try
        {
            Task.WaitAll(left, right);
        }
        catch (AggregateException)
        {
            //handle exceptions here
        }
    }

    // By using Parallel.Invoke
    public static void DoTree2<T>(Tree<T> tree, Action<T> action)
    {
        if (tree == null) return;
        Parallel.Invoke(
            () => DoTree2(tree.Left, action),
            () => DoTree2(tree.Right, action),
            () => action(tree.Data)
        );
    }
}

Imports System.Threading.Tasks

Public Class TreeWalk

    Shared Sub Main()

        Dim tree As Tree(Of Person) = New Tree(Of Person)()

        ' ...populate tree (left as an exercise)

        ' Define the Action to perform on each node.
        Dim myAction As Action(Of Person) = New Action(Of Person)(Sub(x)
                                                                      Console.WriteLine("{0}  : {1} ", x.Name, x.Number)
                                                                  End Sub)

        ' Traverse the tree with parallel tasks.
        DoTree(tree, myAction)
    End Sub

    Public Class Person
        Public Name As String
        Public Number As Integer
    End Class

    Public Class Tree(Of T)
        Public Left As Tree(Of T)
        Public Right As Tree(Of T)
        Public Data As T
    End Class

    ' By using tasks explicitly.
    Public Shared Sub DoTree(Of T)(ByVal myTree As Tree(Of T), ByVal a As Action(Of T))
        If myTree Is Nothing Then
            Return
        End If
        Dim left = Task.Factory.StartNew(Sub() DoTree(myTree.Left, a))
        Dim right = Task.Factory.StartNew(Sub() DoTree(myTree.Right, a))
        a(myTree.Data)

        Try
            Task.WaitAll(left, right)
        Catch ae As AggregateException
            'handle exceptions here
        End Try
    End Sub

    ' By using Parallel.Invoke
    Public Shared Sub DoTree2(Of T)(ByVal myTree As Tree(Of T), ByVal myAct As Action(Of T))
        If myTree Is Nothing Then
            Return
        End If
        Parallel.Invoke(
            Sub() DoTree2(myTree.Left, myAct),
            Sub() DoTree2(myTree.Right, myAct),
            Sub() myAct(myTree.Data)
        )
    End Sub
End Class

표시된 두 메서드는 기능적으로 동일합니다. StartNew 메서드를 사용하여 작업을 만들고 실행하면, 작업으로부터 핸들을 받아 이를 통해 작업을 대기하고 예외를 처리할 수 있습니다.

참고하십시오

• TPL(작업 병렬 라이브러리)