Parallel.for 循环执行

Question

Scenario

I need to create n threads ( not equal to number of function to executes) that execute multiple functions parallel. So my code is

    static void Main() 
    { 
        Parallel.For(0, 2, i => // it creates 2 threads as number of iterations.why?
            {
                  method1();
                  method2();
                  method3();
                  method4();
                  method5();
                  method6();
                  method7();
                  method8();
                  method9();
                  method10();
            });
     }

How to use MaxDegreeOfParallelism property here in best way? Can someone please help?

Answer 1

It seems that you are looking for Parallel.Invoke instead of Parallel.For (I can't see any loop in your code):

  ParallelOptions options = new ParallelOptions() {
    //TODO: carry out experiment on your workstation to find out the right number
    MaxDegreeOfParallelism = 4, 
  };

  // Run method1..method10 in parallel while using options 
  Parallel.Invoke(options,
    method1,
    method2,
    method3,
    method4,
    method5,
    method6,
    method7,
    method8,
    method9,
    method10
  );

Answer 2

As you wish

var methods = new Action[] {
    method1, method2, method3, method4, method5, method6, method7, method8, method9, method10 };

Parallel.For(0, methods.Length, i =>
{
    methods[i]();
});

This way you can set the degree of parallelization

var options = new ParallelOptions { MaxDegreeOfParallelism = 4 };

Parallel.For(0, methods.Length, options, i =>

---

When you wrote Parallel.For(0, 2 , it creates a loop for the specified number of elements: from 0 (inclusive) to 2 (exclusive). Therefore, there can be a maximum of two threads.