Procedura: utilizzare Parallel.Invoke per eseguire operazioni in parallelo
Questo esempio mostra come parallelizzare le operazioni usando Invoke in Task Parallel Library. Vengono eseguite tre operazioni in un'origine dati condivisa. Le operazioni possono essere eseguite in parallelo in modo semplice, perché nessuna delle operazioni modifica l'origine.
Nota
Questa documentazione usa espressioni lambda per definire delegati in TPL. Se non si ha familiarità con le espressioni lambda in C# o Visual Basic, vedere Espressioni lambda in PLINQ e TPL.
Esempio
namespace ParallelTasks
{
using System;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
class ParallelInvoke
{
static void Main()
{
// Retrieve Goncharov's "Oblomov" from Gutenberg.org.
string[] words = CreateWordArray(@"http://www.gutenberg.org/files/54700/54700-0.txt");
#region ParallelTasks
// Perform three tasks in parallel on the source array
Parallel.Invoke(
() =>
{
Console.WriteLine("Begin first task...");
GetLongestWord(words);
}, // close first Action
() =>
{
Console.WriteLine("Begin second task...");
GetMostCommonWords(words);
}, //close second Action
() =>
{
Console.WriteLine("Begin third task...");
GetCountForWord(words, "sleep");
} //close third Action
); //close parallel.invoke
Console.WriteLine("Returned from Parallel.Invoke");
#endregion
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
#region HelperMethods
private static void GetCountForWord(string[] words, string term)
{
var findWord = from word in words
where word.ToUpper().Contains(term.ToUpper())
select word;
Console.WriteLine($@"Task 3 -- The word ""{term}"" occurs {findWord.Count()} times.");
}
private static void GetMostCommonWords(string[] words)
{
var frequencyOrder = from word in words
where word.Length > 6
group word by word into g
orderby g.Count() descending
select g.Key;
var commonWords = frequencyOrder.Take(10);
StringBuilder sb = new StringBuilder();
sb.AppendLine("Task 2 -- The most common words are:");
foreach (var v in commonWords)
{
sb.AppendLine(" " + v);
}
Console.WriteLine(sb.ToString());
}
private static string GetLongestWord(string[] words)
{
var longestWord = (from w in words
orderby w.Length descending
select w).First();
Console.WriteLine($"Task 1 -- The longest word is {longestWord}.");
return longestWord;
}
// An http request performed synchronously for simplicity.
static string[] CreateWordArray(string uri)
{
Console.WriteLine($"Retrieving from {uri}");
// Download a web page the easy way.
string s = new WebClient().DownloadString(uri);
// Separate string into an array of words, removing some common punctuation.
return s.Split(
new char[] { ' ', '\u000A', ',', '.', ';', ':', '-', '_', '/' },
StringSplitOptions.RemoveEmptyEntries);
}
#endregion
}
}
// The example displays output like the following:
// Retrieving from http://www.gutenberg.org/files/54700/54700-0.txt
// Begin first task...
// Begin second task...
// Begin third task...
// Task 2 -- The most common words are:
// Oblomov
// himself
// Schtoltz
// Gutenberg
// Project
// another
// thought
// Oblomov's
// nothing
// replied
//
// Task 1 -- The longest word is incomprehensible.
// Task 3 -- The word "sleep" occurs 57 times.
// Returned from Parallel.Invoke
// Press any key to exit
Imports System.Net
Imports System.Threading.Tasks
Module ParallelTasks
Sub Main()
' Retrieve Goncharov's "Oblomov" from Gutenberg.org.
Dim words As String() = CreateWordArray("http://www.gutenberg.org/files/54700/54700-0.txt")
'#Region "ParallelTasks"
' Perform three tasks in parallel on the source array
Parallel.Invoke(Sub()
Console.WriteLine("Begin first task...")
GetLongestWord(words)
' close first Action
End Sub,
Sub()
Console.WriteLine("Begin second task...")
GetMostCommonWords(words)
'close second Action
End Sub,
Sub()
Console.WriteLine("Begin third task...")
GetCountForWord(words, "sleep")
'close third Action
End Sub)
'close parallel.invoke
Console.WriteLine("Returned from Parallel.Invoke")
'#End Region
Console.WriteLine("Press any key to exit")
Console.ReadKey()
End Sub
#Region "HelperMethods"
Sub GetCountForWord(ByVal words As String(), ByVal term As String)
Dim findWord = From word In words
Where word.ToUpper().Contains(term.ToUpper())
Select word
Console.WriteLine($"Task 3 -- The word ""{term}"" occurs {findWord.Count()} times.")
End Sub
Sub GetMostCommonWords(ByVal words As String())
Dim frequencyOrder = From word In words
Where word.Length > 6
Group By word
Into wordGroup = Group, Count()
Order By wordGroup.Count() Descending
Select wordGroup
Dim commonWords = From grp In frequencyOrder
Select grp
Take (10)
Dim s As String
s = "Task 2 -- The most common words are:" & vbCrLf
For Each v In commonWords
s = s & v(0) & vbCrLf
Next
Console.WriteLine(s)
End Sub
Function GetLongestWord(ByVal words As String()) As String
Dim longestWord = (From w In words
Order By w.Length Descending
Select w).First()
Console.WriteLine($"Task 1 -- The longest word is {longestWord}.")
Return longestWord
End Function
' An http request performed synchronously for simplicity.
Function CreateWordArray(ByVal uri As String) As String()
Console.WriteLine($"Retrieving from {uri}")
' Download a web page the easy way.
Dim s As String = New WebClient().DownloadString(uri)
' Separate string into an array of words, removing some common punctuation.
Return s.Split(New Char() {" "c, ControlChars.Lf, ","c, "."c, ";"c, ":"c,
"-"c, "_"c, "/"c}, StringSplitOptions.RemoveEmptyEntries)
End Function
#End Region
End Module
' The example displays output like the following:
' Retrieving from http://www.gutenberg.org/files/54700/54700-0.txt
' Begin first task...
' Begin second task...
' Begin third task...
' Task 2 -- The most common words are:
' Oblomov
' himself
' Schtoltz
' Gutenberg
' Project
' another
' thought
' Oblomov's
' nothing
' replied
'
' Task 1 -- The longest word is incomprehensible.
' Task 3 -- The word "sleep" occurs 57 times.
' Returned from Parallel.Invoke
' Press any key to exit
Con Invoke, basta indicare le azioni che si desidera eseguire simultaneamente e il runtime gestisce tutti i dettagli di pianificazione dei thread, tra cui l'adattamento automatico al numero di core nel computer host.
Questo esempio parallelizza le operazioni, ma non i dati. Come approccio alternativo, è possibile parallelizzare le query LINQ usando PLINQ ed eseguire le query in sequenza. In alternativa, è possibile parallelizzare i dati usando PLINQ. Un'altra possibilità consiste nel parallelizzare sia le query che le attività. Anche se il sovraccarico risultante potrebbe comportare problemi di prestazioni nei computer host con un numero relativamente basso di processori, la scalabilità è decisamente migliore nei computer con molti processori.
Compilare il codice
Copiare e incollare l'esempio completo in un progetto di Microsoft Visual Studio e premere F5.
Vedi anche
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