Question

In my previous question how to suspend a thread for 1 ms? it was answered that to introduce delay of 1 ms I should use Timer.

I need to “do work” then wait 2 ms in average (1-5 ms is ok, it’s ok to have rarely extreme delays up to several hundreads ms), then do work again. It’s important not to try to start new iteration when previous iteration still not finished, so I don’t need to do something every 1-5 ms, I need 1-5 ms delay between iterations.

I’ve tried to do that using System.Timers.Timer but it doesn’t work:

using System;
using System.Diagnostics;
using System.Threading;
using System.Timers;
using Timer = System.Timers.Timer;

namespace TestTimer
{
    class Program
    {
        static Timer refresh_timer;
        private static int called;
        private const int ITERATIONS = 100;
        private static Stopwatch sw;

        static void Main(string[] args)
        {
            refresh_timer = new Timer(1);
            refresh_timer.AutoReset = false;
            refresh_timer.Elapsed += OnRefreshTimedEvent;
            sw = Stopwatch.StartNew();
            refresh_timer.Start();
            Thread.Sleep(10000);
        }

        static void OnRefreshTimedEvent(object source, ElapsedEventArgs args)
        {
            DoGateIteration();
        }

        private static void DoGateIteration()
        {
            //try
            //{
                // work here
                called++;
            //}
            //finally
            //{
                if (called == ITERATIONS)
                {
                    Console.WriteLine("Average iterations per second: " + ITERATIONS * 1000 / sw.ElapsedMilliseconds);
                    Console.WriteLine("Average iterations milliseconds: " + sw.ElapsedMilliseconds / ITERATIONS);
                }
                refresh_timer.Start();
            //}
        }
    }
}

It reports:

Average iterations per second: 64
Average iterations milliseconds: 15

So it seems System.Timers.Timer is not as precise as I need.
Probably I should try System.Threading.Timer, but this timer doesn’t have AutoReset property that I need.

What would you suggest?

Answer 1

For such a short delay of only 1 or 2 milliseconds, it’s probably best just to busy-wait:

private static int called;
private const int ITERATIONS = 10000;
private static Stopwatch sw;

static void Main(string[] args)
{
    sw = Stopwatch.StartNew();

    var x = Stopwatch.StartNew();
    while (true)
    {
        DoGateIteration();

        x.Restart();
        while (x.ElapsedMilliseconds < 2) ; // busy-wait for 2 ms
    }
}

private static void DoGateIteration()
{
    called++;
    if (called == ITERATIONS)
    {
        Console.WriteLine("Average iterations per second: " + ITERATIONS * 1000 / sw.ElapsedMilliseconds);
        Console.WriteLine("Average iterations milliseconds: " + sw.ElapsedMilliseconds / ITERATIONS);
    }
}

Output:

Average iterations per second: 500
Average iterations milliseconds: 2