Question

using System;
using System.Threading;
using System.Threading.Tasks;

class Program
{
    static void Main()
    {
        double[] numbers = new double[10000];

        Parallel.For(0, 9999, index => numbers[index] = index * 3);

        Thread.MemoryBarrier();

        // do something with numbers
    }
}

Is the MemoryBarrier() required above, or does the Parallel.For have a ‘built in’ memory barrier?

Answer 1

There is no need for the memory barrier, when you do a Parallel.For the thread that calls the function waits for the end of the tasks, if it waits, it probably uses some synchronizer, to notify a waitting thread, when a synchronizer notifues “it is needed” to have a release barrier, a release barrier garanties that all changes done in the code above are visible globally, so you don’t need the memory.barrier