Compartir a través de

Procedimiento para recorrer un árbol binario con tareas en paralelo

  • Artículo

En el ejemplo siguiente se muestran dos formas de usar las tareas paralelas para recorrer una estructura de datos en árbol. La creación del árbol se deja como un ejercicio.

Ejemplo

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("{0} : {1}", 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

Los dos métodos que se muestran son funcionalmente equivalentes. Con el uso del método StartNew para crear y ejecutar las tareas, estas devuelven un identificador que puede usarse para esperar las tareas y controlar excepciones.

Vea también