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Parallel processing pattern
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using System; | |
using System.Collections.Concurrent; | |
using System.Linq; | |
using System.Threading; | |
using System.Threading.Tasks; | |
// the task is to Analyze() files in parallel and Process() them on the main thread in batches | |
var files = Enumerable.Range(0, 1000).Select(x => $"File{x:0000}.cs").ToList(); | |
var degreeOfParallelism = Math.Min(Environment.ProcessorCount, 8); | |
var unfinishedJob = new ConcurrentBag<string>(files); | |
var itemsToProcessBatch = 10; | |
var toProcess = new ConcurrentBag<string>(); | |
var toProcessCount = 0; | |
while (unfinishedJob.Count > 0) | |
{ | |
// do Analyze() in parallel on background threads | |
Task.WaitAll(Enumerable | |
.Range(0, degreeOfParallelism) | |
.Select(workerIndex => | |
{ | |
// can take some time, better to use long-running tasks? | |
return Task.Run(() => | |
{ | |
while (unfinishedJob.TryTake(out var workItem)) | |
{ | |
if (Analyze(workerIndex, workItem)) | |
{ | |
toProcess.Add(workItem); | |
} | |
var incremented = Interlocked.Increment(ref toProcessCount); | |
if (incremented > itemsToProcessBatch) | |
{ | |
Console.Write('*'); | |
return; // time to process | |
} | |
} | |
}); | |
}) | |
.ToArray()); | |
Console.WriteLine(); | |
// process the work items sequentially on the main thread | |
while (toProcess.TryTake(out var workItem)) | |
{ | |
Process(workItem); | |
} | |
toProcessCount = 0; | |
} | |
bool Analyze(int workerIndex, string workItem) | |
{ | |
Thread.Sleep(100); | |
var include = workItem.GetHashCode() % 20 == 0; | |
Console.Write(include ? $"[{workerIndex}]" : workerIndex.ToString()); | |
return include; // 5% | |
} | |
void Process(string workItem) | |
{ | |
Console.WriteLine($"Processing {workItem}"); | |
Thread.Sleep(200); | |
} |
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