64 lines
1.9 KiB
C#
64 lines
1.9 KiB
C#
// ----------------------------------------------------------------------------
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//
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// ----------------------------------------------------------------------------
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using System;
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using Microsoft.Contracts;
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namespace Microsoft.Singularity.Applications.Benchmarks.DiskRW
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{
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/// <summary>
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/// Low-cost Integer random number generator. The
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/// implementation is based on the description of Park and
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/// Miller's RNG on page 278 of Numerical Recipes in C, 2nd
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/// Edition, by Press, Teukolsky, Vetterling, and Flannery.
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///
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/// The same random number generator is used for our disk
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/// benchmarks on other platforms.
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/// </summary>
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public class SRandom
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{
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public const uint Maximum = 0x7fffffffu;
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const ulong m = 2147483647;
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const ulong a = 16807;
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const uint initialValue = 0x23456789;
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uint last;
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public SRandom()
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{
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Reset();
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}
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[Delayed]
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public void Reset()
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{
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last = initialValue;
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}
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public int Next()
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{
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// Use 64-bit multiplication to preserve high bits.
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ulong tmp = (a * last) % m;
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last = (uint) tmp;
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return (int)(last & Maximum);
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}
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public static void Check()
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{
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const int test_iterations = 10000000;
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SRandom r = new SRandom();
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int hash = 0;
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for (int i = 0; i < test_iterations; i++) {
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int n = r.Next();
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System.Diagnostics.Debug.Assert(n != 0);
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hash ^= n;
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}
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Console.Write("xor sum 1...{0} = {1}\n", test_iterations, hash);
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System.Diagnostics.Debug.Assert(hash == 1080076236);
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}
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}
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}
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