Re: Why is Stopwatch.ElapsedTicks negative?

I'll see if I can come up with a simple repro. For now I'll include a
snippet of the code which shows how I use the stopwatch instance.

long[] durations = new long[1024L * 1024L / bufferSize];
Stopwatch stopwatch = new Stopwatch();

Console.WriteLine("Ready to start writing. Press any key to continue.");
Console.ReadLine();
DateTime start = DateTime.Now;
Console.WriteLine("Starting.");

// Write buffers.

for (int i = 0; i < 1024 * 1024 / bufferSize; ++i)
    {
    stopwatch.Reset();
    stopwatch.Start();
    ulong offset = (ulong) i * 1024L * 1024L;
    IntPtr dataView = Win32.File.MapViewOfFile(dataMap,
Win32.File.FILE_MAP_WRITE,
            (uint) (offset >> 32), (uint) (offset & uint.MaxValue), (uint) bufferSize
* 1024);
    if (dataView == IntPtr.Zero)
        {
        result = Marshal.GetLastWin32Error();
        throw(new Win32Exception(result, string.Format(
                "Failed mapping view ({0}, {1}) of file '{2}', result = {3}",
                offset, bufferSize * 1024, args[0], result)));
        }
    try
        {
        Marshal.Copy(buffer, 0, dataView, buffer.Length);
        }
    finally
        {
        if (flushview == true)
            {
            Win32.File.FlushViewOfFile(dataView, (uint) bufferSize * 1024);
            }
        Win32.File.UnmapViewOfFile(dataView);
        }

    stopwatch.Stop();
    durations[i] = stopwatch.ElapsedTicks;
    if (stopwatch.ElapsedTicks < 0)
        {
        Console.WriteLine("ElapsedTicks < 0, i = {0}, elapsed ticks = {1}, " +
                "elapsed milliseconds = {2}, IsHighResolution = {3}, frequency = {4}",
                i, stopwatch.ElapsedTicks, stopwatch.ElapsedMilliseconds,
                Stopwatch.IsHighResolution, Stopwatch.Frequency);
        }
    }
DateTime end = DateTime.Now;
Console.WriteLine("Finished.");

long min = long.MaxValue;
long max = long.MinValue;
long average = 0;

for (int i = 0; i < durations.Length; ++i)
    {
    average += durations[i];
    if (durations[i] > max)
        max = durations[i];
    if (durations[i] < min)
        {
        min = durations[i];
        if (min < 0)
            Console.WriteLine("Min has gone below zero, duration: {0}", durations[i]);
        }
    }

Console.WriteLine("duration: {0}", end - start);
Console.WriteLine("min: {0}", min * 1000000 / Stopwatch.Frequency);
Console.WriteLine("max: {0}", max * 1000000 / Stopwatch.Frequency);
Console.WriteLine("average: {0}", (average / durations.Length) * 1000000 /
Stopwatch.Frequency);

--
Thanks,
Nick

nicknospamdu@community.nospam
remove "nospam" change community. to msn.com

"Peter Duniho" wrote: