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  1. using System;
  2. using System.Collections.Concurrent;
  3. using System.Diagnostics.Contracts;
  4. using System.Linq;
  5. using System.Threading.Tasks;
  6.  
  7. namespace BenchApp
  8. {
  9.     class Program
  10.     {
  11.         static void Main(string[] args)
  12.         {
  13.             double[] a = new double[16 * 1024 * 1024];
  14.             Random rnd = new Random(0);
  15.             for (int i = 0; i < a.Length; i++)
  16.             {
  17.                 a[i] = rnd.NextDouble() * rnd.Next(1000);
  18.             }
  19.             var etalonSum = Enumerable.Sum(a);
  20.  
  21.             var anothersum = a.Sum();
  22.             Console.WriteLine(etalonSum);
  23.             Console.WriteLine(anothersum);
  24.         }
  25.     }
  26.  
  27.     public static class Test
  28.     {
  29.         [Pure]
  30.         public static double Sum(this double[] source)
  31.         {
  32.             if (source.Length < Constants.SingleThreadExecutionThreshold)
  33.                 return Sum(source, 0, source.Length);
  34.             double result = 0;
  35.             object syncRoot = new object();
  36.             Parallel.ForEach(Partitioner.Create(0, source.Length),
  37.                 () => (double)0,
  38.                 (range, state, sum) => Sum(source, range.Item1, range.Item2),
  39.                 x =>
  40.                 {
  41.                     lock (syncRoot)
  42.                         result += x;
  43.                 });
  44.  
  45.             return result;
  46.         }
  47.         [Pure]
  48.         private static double Sum(this double[] source, int startIndex, int endIndex)
  49.         {
  50.             double sum1 = 0, sum2 = 0, sum3 = 0, sum4 = 0;
  51.             checked
  52.             {
  53.                 int i;
  54.                 for (i = startIndex; i < endIndex - Constants.Step + 1; i += Constants.Step)
  55.                 {
  56.                     sum1 += source[i];
  57.                     sum2 += source[i + 1];
  58.                     sum3 += source[i + 2];
  59.                     sum4 += source[i + 3];
  60.                 }
  61.                 if (i == source.Length)
  62.                     return ((sum1 + sum2) + (sum3 + sum4));
  63.                 if (i == source.Length - 1)
  64.                     return ((sum1 + sum2) + (sum3 + sum4) + source[i]);
  65.                 if (i == source.Length - 2)
  66.                     return ((sum1 + sum2) + (sum3 + sum4) + (source[i] + source[i + 1]));
  67.                 return ((sum1 + sum2) + (sum3 + sum4) + (source[i] + source[i + 1] + source[i + 2]));
  68.             }
  69.         }
  70.  
  71.         internal static class Constants
  72.         {
  73.             public const int Step = 4;
  74.             public const int SingleThreadExecutionThreshold = 1024;
  75.         }
  76.     }
  77. }
Success #stdin #stdout 2.3s 27352KB
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4188981720.25181
349297181.322729
https://ideone.com/8sD0JL
language:
C# (gmcs 5.20.1)
created:
8 years ago
visibility:
public

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