How Does Parallel.ForEach Improve Performance Compared to a Traditional Foreach Loop in .NET?

Parallel Processing with Parallel.ForEach

Parallel programming enhances application performance by harnessing multiple processor cores. Parallel.ForEach is a powerful construct that simplifies parallel processing in .NET applications.

Foreach Loop vs. Parallel.ForEach

The traditional foreach loop performs iterations sequentially on a single thread. Parallel.ForEach, on the other hand, distributes the workload across multiple threads, enabling simultaneous execution of iterations.

Characteristics of Foreach Loops:

• Sequential execution of iterations
• Single thread utilization
• Ideal for quick operations where threading overhead is not significant

Characteristics of Parallel.ForEach:

• Parallel execution of iterations
• Multiple threads utilization
• Beneficial for slow operations where parallelization improves performance

Converting to Parallel.ForEach

To convert the given code snippet to Parallel.ForEach:

Parallel.ForEach(list_lines, line =>
{
    // My Stuff
});

Example

The following example demonstrates the difference between a foreach loop and Parallel.ForEach:

using System;
using System.Diagnostics;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace ParallelForEachExample
{
    class Program
    {
        static void Main()
        {
            var lines = File.ReadAllLines("proxylist.txt");
            var list_lines = new List<string>(lines);

            Console.WriteLine("Traditional foreach loop");
            var watch = Stopwatch.StartNew();
            foreach (var line in list_lines)
            {
                Console.WriteLine(line);
                Thread.Sleep(10);
            }
            watch.Stop();
            Console.WriteLine($"foreach loop execution time: {watch.ElapsedMilliseconds} ms");

            Console.WriteLine("Using Parallel.ForEach");
            watch = Stopwatch.StartNew();
            Parallel.ForEach(list_lines, line =>
            {
                Console.WriteLine(line);
                Thread.Sleep(10);
            });
            watch.Stop();
            Console.WriteLine($"Parallel.ForEach() execution time: {watch.ElapsedMilliseconds} ms");
        }
    }
}

Output

The output will demonstrate that Parallel.ForEach executes the iterations in parallel, reducing the overall processing time compared to the traditional foreach loop.

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