// <copyright file="Hartley.Naive.cs" company="Math.NET">
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// Math.NET Numerics, part of the Math.NET Project
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// http://numerics.mathdotnet.com
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// http://github.com/mathnet/mathnet-numerics
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//
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// Copyright (c) 2009-2014 Math.NET
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//
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// Permission is hereby granted, free of charge, to any person
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// obtaining a copy of this software and associated documentation
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// files (the "Software"), to deal in the Software without
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// restriction, including without limitation the rights to use,
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// copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following
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// conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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// OTHER DEALINGS IN THE SOFTWARE.
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// </copyright>
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using System;
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using IStation.Numerics.Threading;
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namespace IStation.Numerics.IntegralTransforms
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{
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/// <summary>
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/// Fast (FHT) Implementation of the Discrete Hartley Transform (DHT).
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/// </summary>
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public static partial class Hartley
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{
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/// <summary>
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/// Naive generic DHT, useful e.g. to verify faster algorithms.
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/// </summary>
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/// <param name="samples">Time-space sample vector.</param>
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/// <returns>Corresponding frequency-space vector.</returns>
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internal static double[] Naive(double[] samples)
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{
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var w0 = Constants.Pi2/samples.Length;
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var spectrum = new double[samples.Length];
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CommonParallel.For(0, samples.Length, (u, v) =>
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{
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for (int i = u; i < v; i++)
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{
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var wk = w0*i;
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var sum = 0.0;
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for (var n = 0; n < samples.Length; n++)
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{
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var w = n*wk;
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sum += samples[n]*Constants.Sqrt2*Math.Cos(w - Constants.PiOver4);
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}
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spectrum[i] = sum;
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}
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});
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return spectrum;
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}
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}
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}
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