How to: Specify Merge Options in PLINQ
This example shows how to specify the merge options that will apply to all subsequent operators in a PLINQ query. You do not have to set merge options explicitly, but doing so may improve performance. For more information about merge options, see Merge Options in PLINQ.
Caution
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This example is intended to demonstrate usage, and might not run faster than the equivalent sequential LINQ to Objects query. For more information about speedup, see Understanding Speedup in PLINQ. |
The following example demonstrates the behavior of merge options in a basic scenario that has an unordered source and applies an expensive function to every element.
namespace MergeOptions { using System; using System.Diagnostics; using System.Linq; using System.Threading; class Program { static void Main(string[] args) { var nums = Enumerable.Range(1, 10000); // Replace NotBuffered with AutoBuffered // or FullyBuffered to compare behavior. var scanLines = from n in nums.AsParallel() .WithMergeOptions(ParallelMergeOptions.NotBuffered) where n % 2 == 0 select ExpensiveFunc(n); Stopwatch sw = Stopwatch.StartNew(); foreach (var line in scanLines) { Console.WriteLine(line); } Console.WriteLine("Elapsed time: {0} ms. Press any key to exit.", sw.ElapsedMilliseconds); Console.ReadKey(); } // A function that demonstrates what a fly // sees when it watches television :-) static string ExpensiveFunc(int i) { Thread.SpinWait(2000000); return String.Format("{0} *****************************************", i); } } }
In cases where the AutoBuffered option incurs an undesirable latency before the first element is yielded, try the NotBuffered option to yield result elements faster and more smoothly.
