public static Func <Task> ParallelForEach <T>(IQueueSource <T> source, ParallelWorker parallelWorker, Func <ForEachInfo <T>, Task> processAsync, Func <Task> onCloseAsync,
ExceptionCollector ec)
{
Func <Task> t = async delegate {
IdleDetector idleDetector = new IdleDetector();
try {
while (true)
{
var item = await source.Dequeue(ec.CancellationToken);
if (!item.HasValue)
{
break;
}
T itemValue = item.Value;
idleDetector.Enter();
await parallelWorker.StartWorkItem
(
async workerId => {
try {
await processAsync(new ForEachInfo <T>(itemValue, 0, workerId, ec.CancellationToken));
}
catch (Exception exc) {
ec.Add(exc);
}
finally {
idleDetector.Leave();
}
},
ec.CancellationToken
);
}
}
finally {
await idleDetector.WaitForIdle(CancellationToken.None);
if (onCloseAsync != null)
{
try {
await onCloseAsync();
}
catch (Exception exc) {
ec.Add(exc);
}
}
}
};
return(t);
}
public static IQueueSource <T> ParallelWhere <T>(this IQueueSource <T> queue, ParallelWorker parallelWorker, Func <T, Task <bool> > predicate, int?capacity = null)
{
AsyncQueue <T> outQueue = new AsyncQueue <T>(capacity ?? 2);
IdleDetector idleDetector = new IdleDetector();
Func <Task> workPoster = async delegate {
while (true)
{
Option <T> item = await queue.Dequeue(CancellationToken.None);
if (!item.HasValue)
{
break;
}
T itemValue = item.Value;
idleDetector.Enter();
Task doingWork = await parallelWorker.StartWorkItem
(
async (int workerId) => {
try {
if (await predicate(itemValue))
{
await outQueue.Enqueue(itemValue, CancellationToken.None);
}
}
finally {
idleDetector.Leave();
}
},
CancellationToken.None
);
}
await idleDetector.WaitForIdle(CancellationToken.None);
outQueue.WriteEof();
};
Task.Run(workPoster);
return(outQueue);
}
