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How can I limit Parallel.ForEach in C#?
Parallel Foreach
Parallel.ForEach loop in C# runs upon multiple threads and processing takes place in a parallel way. Parallel.ForEach loop is not a basic feature of C# and it is available from C# 4.0 and above To use Parallel.ForEach loop we need to import System.Threading.Tasks namespace in using directive.
Foreach
Foreach loop in C# runs upon a single thread and processing takes place sequentially one by one. Foreach loop is a basic feature of C# and it is available from C# 1.0. Its execution is slower than the Parallel.Foreach in most of the cases.
Example 1
static void Main(string[] args){
List<string> alphabets = new List<string>();
alphabets.Add("A");
alphabets.Add("B");
alphabets.Add("C");
alphabets.Add("D");
alphabets.Add("E");
alphabets.Add("F");
alphabets.Add("G");
alphabets.Add("H");
alphabets.Add("I");
alphabets.Add("J");
alphabets.Add("K");
alphabets.Add("L");
alphabets.Add("M");
alphabets.Add("N");
alphabets.Add("O");
alphabets.Add("P");
alphabets.Add("Q");
alphabets.Add("R");
alphabets.Add("S");
alphabets.Add("T");
alphabets.Add("U");
alphabets.Add("V");
alphabets.Add("W");
alphabets.Add("X");
alphabets.Add("Y");
alphabets.Add("Z");
Console.WriteLine("Printing list using foreach loop
");
var stopWatch = Stopwatch.StartNew();
foreach (string alphabet in alphabets){
Console.WriteLine("alphabet Name: {0}, Thread Id= {1}", alphabet, Thread.CurrentThread.ManagedThreadId);
}
Console.WriteLine("foreach loop execution time = {0} seconds
", stopWatch.Elapsed.TotalSeconds);
Console.WriteLine("Printing list using Parallel.ForEach");
stopWatch = Stopwatch.StartNew();
Parallel.ForEach(alphabets, alphabet =>
{
Console.WriteLine("alphabet Name: {0}, Thread Id= {1}", alphabet, Thread.CurrentThread.ManagedThreadId);
}
);
Console.WriteLine("Parallel.ForEach() execution time = {0} seconds", stopWatch.Elapsed.TotalSeconds);
Console.Read();
Console.ReadLine();
}Output
Printing list using foreach loop
alphabet Name: A, Thread Id= 1 alphabet Name: B, Thread Id= 1 alphabet Name: C, Thread Id= 1 alphabet Name: D, Thread Id= 1 alphabet Name: E, Thread Id= 1 alphabet Name: F, Thread Id= 1 alphabet Name: G, Thread Id= 1 alphabet Name: H, Thread Id= 1 alphabet Name: I, Thread Id= 1 alphabet Name: J, Thread Id= 1 alphabet Name: K, Thread Id= 1 alphabet Name: L, Thread Id= 1 alphabet Name: M, Thread Id= 1 alphabet Name: N, Thread Id= 1 alphabet Name: O, Thread Id= 1 alphabet Name: P, Thread Id= 1 alphabet Name: Q, Thread Id= 1 alphabet Name: R, Thread Id= 1 alphabet Name: S, Thread Id= 1 alphabet Name: T, Thread Id= 1 alphabet Name: U, Thread Id= 1 alphabet Name: V, Thread Id= 1 alphabet Name: W, Thread Id= 1 alphabet Name: X, Thread Id= 1 alphabet Name: Y, Thread Id= 1 alphabet Name: Z, Thread Id= 1 foreach loop execution time = 0.0223421 seconds
Printing list using Parallel.ForEach
alphabet Name: A, Thread Id= 1 alphabet Name: G, Thread Id= 4 alphabet Name: H, Thread Id= 4 alphabet Name: I, Thread Id= 4 alphabet Name: J, Thread Id= 4 alphabet Name: K, Thread Id= 4 alphabet Name: L, Thread Id= 4 alphabet Name: N, Thread Id= 4 alphabet Name: O, Thread Id= 4 alphabet Name: P, Thread Id= 4 alphabet Name: Q, Thread Id= 4 alphabet Name: Y, Thread Id= 6 alphabet Name: Z, Thread Id= 6 alphabet Name: D, Thread Id= 6 alphabet Name: E, Thread Id= 6 alphabet Name: F, Thread Id= 6 alphabet Name: T, Thread Id= 6 alphabet Name: U, Thread Id= 6 alphabet Name: V, Thread Id= 6 alphabet Name: R, Thread Id= 4 alphabet Name: M, Thread Id= 5 alphabet Name: S, Thread Id= 7 alphabet Name: B, Thread Id= 1 alphabet Name: C, Thread Id= 1 alphabet Name: W, Thread Id= 6 alphabet Name: X, Thread Id= 6 Parallel.ForEach() execution time = 0.0559777 seconds
Example 2
Limit the Paralleleism in parallel.foreach
static class Program{
static void Main(string[] args){
List<string> alphabets = new List<string>();
alphabets.Add("A");
alphabets.Add("B");
alphabets.Add("C");
alphabets.Add("D");
alphabets.Add("E");
alphabets.Add("F");
alphabets.Add("G");
alphabets.Add("H");
alphabets.Add("I");
alphabets.Add("J");
alphabets.Add("K");
alphabets.Add("L");
alphabets.Add("M");
alphabets.Add("N");
alphabets.Add("O");
alphabets.Add("P");
alphabets.Add("Q");
alphabets.Add("R");
alphabets.Add("S");
alphabets.Add("T");
alphabets.Add("U");
alphabets.Add("V");
alphabets.Add("W");
alphabets.Add("X");
alphabets.Add("Y");
alphabets.Add("Z");
Parallel.ForEach(
alphabets,
new ParallelOptions { MaxDegreeOfParallelism = 2 },
alphabet => { Console.WriteLine("alphabet Name: {0}, Thread Id= {1}", alphabet, Thread.CurrentThread.ManagedThreadId); }
);
}
}Output
alphabet Name: N, Thread Id= 4 alphabet Name: O, Thread Id= 4 alphabet Name: P, Thread Id= 4 alphabet Name: A, Thread Id= 1 alphabet Name: B, Thread Id= 1 alphabet Name: C, Thread Id= 1 alphabet Name: Q, Thread Id= 4 alphabet Name: R, Thread Id= 4 alphabet Name: S, Thread Id= 4 alphabet Name: T, Thread Id= 4 alphabet Name: U, Thread Id= 4 alphabet Name: V, Thread Id= 4 alphabet Name: W, Thread Id= 4 alphabet Name: X, Thread Id= 4 alphabet Name: Y, Thread Id= 4 alphabet Name: Z, Thread Id= 4 alphabet Name: H, Thread Id= 4 alphabet Name: I, Thread Id= 4 alphabet Name: J, Thread Id= 4 alphabet Name: K, Thread Id= 4 alphabet Name: D, Thread Id= 1 alphabet Name: L, Thread Id= 4 alphabet Name: E, Thread Id= 1 alphabet Name: F, Thread Id= 1 alphabet Name: G, Thread Id= 1 alphabet Name: M, Thread Id= 4
Updated on: 07-Nov-2020
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