private async Task AsyncPipelineBlackBoxConsistencyTest(int workerCount)
{
if (workerCount < 1)
throw new ArgumentOutOfRangeException("You must specify at least one worker.", "workerCount");
int loopCount = _iterationCount / workerCount;
const double variance = 0.1;
int expectedTasksCompleted = loopCount * workerCount;
var delayLength = TimeSpan.FromSeconds(1);
const int pipelineCapacity = _defaultPipelineCapacity;
var pipeline = new AsyncPipeline(pipelineCapacity);
int tasksCompleted = 0;
// the following value is wrapped within an array to avoid a modified closure warning from ReSharper.
int[] pipelineSize = { 0 };
var capacityReached = new InterlockedFlag();
Action workFunc =
() =>
{
var sz = Interlocked.Increment(ref pipelineSize[0]);
CheckPipelineState(sz, pipelineCapacity, capacityReached);
Task.Delay(delayLength).Wait();
Interlocked.Decrement(ref pipelineSize[0]);
Interlocked.Increment(ref tasksCompleted);
};
Action workerFunc =
() =>
{
for (var j = 0; j < loopCount; j++)
{
Task task = new Task(workFunc);
pipeline.Add(task, whiteBox: null);
task.Start();
}
};
Func<Task> monitorFunc =
async () =>
{
var delay = TimeSpan.FromSeconds(5);
while (tasksCompleted < expectedTasksCompleted)
{
output.WriteLine("test in progress: tasksCompleted = {0}.", tasksCompleted);
await Task.Delay(delay);
}
};
var workers = new Task[workerCount];
var stopwatch = Stopwatch.StartNew();
for (var i = 0; i < workerCount; ++i)
workers[i] = Task.Run(workerFunc);
Task.Run(monitorFunc).Ignore();
await Task.WhenAll(workers);
pipeline.Wait();
stopwatch.Stop();
Assert.AreEqual(expectedTasksCompleted, tasksCompleted, "The test did not complete the expected number of tasks.");
var targetTimeSec = expectedTasksCompleted * delayLength.TotalSeconds / pipelineCapacity;
var minTimeSec = (1.0 - variance) * targetTimeSec;
var maxTimeSec = (1.0 + variance) * targetTimeSec;
var actualSec = stopwatch.Elapsed.TotalSeconds;
output.WriteLine(
"Test finished in {0} sec, {1}% of target time {2} sec. Permitted variance is +/-{3}%",
actualSec,
actualSec / targetTimeSec * 100,
targetTimeSec,
variance * 100);
Assert.IsTrue(capacityReached.IsSet, "Pipeline capacity not reached; the delay length probably is too short to be useful.");
Assert.IsTrue(
actualSec >= minTimeSec,
string.Format("The unit test completed too early ({0} sec < {1} sec).", actualSec, minTimeSec));
Assert.IsTrue(
actualSec <= maxTimeSec,
string.Format("The unit test completed too late ({0} sec > {1} sec).", actualSec, maxTimeSec));
}
private void CheckPipelineState(int size, int capacity, InterlockedFlag capacityReached)
{
Assert.IsTrue(size >= 0);
Assert.IsTrue(capacity > 0);
// a understood flaw of the current algorithm is that the capacity can be exceeded by one item. we've decided that this is acceptable and we allow it to happen.
Assert.IsTrue(size <= capacity, string.Format("size ({0}) must be less than the capacity ({1})", size, capacity));
if (capacityReached != null && size == capacity)
capacityReached.TrySet();
}
