From 01d2a9ce623726557949aebb83e497ae2afa21e4 Mon Sep 17 00:00:00 2001
From: Christoph Ruegg <git@cdrnet.ch>
Date: Fri, 28 Oct 2016 15:09:49 +0200
Subject: [PATCH] FFT: tests to verify real against complex, and real forward
 to inverse

---
 .../InverseTransformTest.cs                   | 19 ++++++++++
 .../MatchingNaiveTransformTest.cs             | 36 +++++++++++++++----
 2 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/src/UnitTests/IntegralTransformsTests/InverseTransformTest.cs b/src/UnitTests/IntegralTransformsTests/InverseTransformTest.cs
index 19211a14..7db77ffc 100644
--- a/src/UnitTests/IntegralTransformsTests/InverseTransformTest.cs
+++ b/src/UnitTests/IntegralTransformsTests/InverseTransformTest.cs
@@ -109,6 +109,25 @@ namespace MathNet.Numerics.UnitTests.IntegralTransformsTests
             AssertHelpers.AlmostEqual(samples, work, 10);
         }
 
+        /// <summary>
+        /// Fourier bluestein is reversible.
+        /// </summary>
+        /// <param name="options">Fourier options.</param>
+        [TestCase(FourierOptions.Default)]
+        [TestCase(FourierOptions.Matlab)]
+        public void FourierRealIsReversible(FourierOptions options)
+        {
+            var samples = Generate.Random(0x7FFF, GetUniform(1));
+            var work = new double[samples.Length+2];
+            samples.CopyTo(work, 0);
+
+            Fourier.ForwardReal(work, samples.Length, options);
+            Assert.IsFalse(work.ListAlmostEqual(samples, 6));
+
+            Fourier.InverseReal(work, samples.Length, options);
+            AssertHelpers.AlmostEqual(samples, work, 10);
+        }
+
         /// <summary>
         /// Hartley naive is reversible.
         /// </summary>
diff --git a/src/UnitTests/IntegralTransformsTests/MatchingNaiveTransformTest.cs b/src/UnitTests/IntegralTransformsTests/MatchingNaiveTransformTest.cs
index e40185d5..2fc25462 100644
--- a/src/UnitTests/IntegralTransformsTests/MatchingNaiveTransformTest.cs
+++ b/src/UnitTests/IntegralTransformsTests/MatchingNaiveTransformTest.cs
@@ -181,19 +181,41 @@ namespace MathNet.Numerics.UnitTests.IntegralTransformsTests
             VerifyInplace(samples, 10, options, Fourier.Inverse, Fourier.BluesteinInverse);
         }
 
+        [TestCase(FourierOptions.Default, 128)]
+        [TestCase(FourierOptions.Default, 129)]
+        [TestCase(FourierOptions.NoScaling, 128)]
+        [TestCase(FourierOptions.NoScaling, 129)]
+        [TestCase(FourierOptions.AsymmetricScaling, 128)]
+        [TestCase(FourierOptions.AsymmetricScaling, 129)]
+        public void RealMatchesComplex(FourierOptions options, int n)
+        {
+            var real = Generate.Random(n.IsEven() ? n + 2 : n + 1, GetUniform(1));
+            real[n] = 0d;
+            if (n.IsEven()) real[n+1] = 0d;
+            var complex = new Complex[n];
+            for (int i = 0; i < complex.Length; i++)
+            {
+                complex[i] = new Complex(real[i], 0d);
+            }
+
+            Fourier.Forward(complex, options);
+            Fourier.ForwardReal(real, n, options);
+
+            int m = (n + 1)/2;
+            for (int i = 0, j = 0; i < m; i++)
+            {
+                AssertHelpers.AlmostEqual(complex[i], new Complex(real[j++], real[j++]), 10);
+            }
+        }
+
         [Test]
         public void AlgorithmsMatchProvider_PowerOfTwo_Large()
         {
             // 65536 = 2^16
-            const FourierOptions options = FourierOptions.NoScaling;
             var samples = Generate.RandomComplex(65536, GetUniform(1));
 
-            var provider = new Complex[samples.Length];
-            samples.Copy(provider);
-            Control.FourierTransformProvider.Forward(provider, FourierTransformScaling.NoScaling);
-
-            Verify(samples, 10, options, (a, b) => provider, Fourier.Radix2Forward);
-            Verify(samples, 10, options, (a, b) => provider, Fourier.BluesteinForward);
+            VerifyInplace(samples, 10, FourierOptions.NoScaling, (s,o) => Control.FourierTransformProvider.Forward(s, FourierTransformScaling.NoScaling), Fourier.Radix2Forward);
+            VerifyInplace(samples, 10, FourierOptions.NoScaling, (s, o) => Control.FourierTransformProvider.Forward(s, FourierTransformScaling.NoScaling), Fourier.BluesteinForward);
         }
 
         [Test]