From 787e32562ca34cde8afacf5e1d8ee4782d9c6d11 Mon Sep 17 00:00:00 2001
From: Christoph Ruegg <git@cdrnet.ch>
Date: Tue, 15 Nov 2016 09:46:07 +0100
Subject: [PATCH] LA: add Vector.AsArray to directly return internal arrays if
 the schema is matching

---
 src/Numerics/LinearAlgebra/Matrix.cs          |  1 -
 .../Storage/DenseVectorStorage.cs             | 14 +++++++++++++
 .../Storage/SparseVectorStorage.cs            | 12 +++++++++++
 .../LinearAlgebra/Storage/VectorStorage.cs    | 17 ++++++++++++++++
 src/Numerics/LinearAlgebra/Vector.cs          | 20 +++++++++++++------
 5 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/src/Numerics/LinearAlgebra/Matrix.cs b/src/Numerics/LinearAlgebra/Matrix.cs
index 6eb2e3d3..f11423f7 100644
--- a/src/Numerics/LinearAlgebra/Matrix.cs
+++ b/src/Numerics/LinearAlgebra/Matrix.cs
@@ -1376,7 +1376,6 @@ namespace MathNet.Numerics.LinearAlgebra
         /// Otherwise returns null. Changes to the returned array and the matrix will affect each other.
         /// Use ToArray instead if you always need an independent array.
         /// </summary>
-        /// <returns>A multidimensional containing the values of this matrix.</returns>
         public T[,] AsArray()
         {
             return Storage.AsArray();
diff --git a/src/Numerics/LinearAlgebra/Storage/DenseVectorStorage.cs b/src/Numerics/LinearAlgebra/Storage/DenseVectorStorage.cs
index 1404b495..f5ba1401 100644
--- a/src/Numerics/LinearAlgebra/Storage/DenseVectorStorage.cs
+++ b/src/Numerics/LinearAlgebra/Storage/DenseVectorStorage.cs
@@ -329,6 +329,20 @@ namespace MathNet.Numerics.LinearAlgebra.Storage
             }
         }
 
+        // EXTRACT
+
+        public override T[] ToArray()
+        {
+            var ret = new T[Data.Length];
+            Array.Copy(Data, 0, ret, 0, Data.Length);
+            return ret;
+        }
+
+        public override T[] AsArray()
+        {
+            return Data;
+        }
+
         // ENUMERATION
 
         public override IEnumerable<T> Enumerate()
diff --git a/src/Numerics/LinearAlgebra/Storage/SparseVectorStorage.cs b/src/Numerics/LinearAlgebra/Storage/SparseVectorStorage.cs
index d2f351b1..e474cedd 100644
--- a/src/Numerics/LinearAlgebra/Storage/SparseVectorStorage.cs
+++ b/src/Numerics/LinearAlgebra/Storage/SparseVectorStorage.cs
@@ -611,6 +611,18 @@ namespace MathNet.Numerics.LinearAlgebra.Storage
             }
         }
 
+        // EXTRACT
+
+        public override T[] ToArray()
+        {
+            var ret = new T[Length];
+            for (int i = 0; i < ValueCount; i++)
+            {
+                ret[Indices[i]] = Values[i];
+            }
+            return ret;
+        }
+
         // ENUMERATION
 
         public override IEnumerable<T> Enumerate()
diff --git a/src/Numerics/LinearAlgebra/Storage/VectorStorage.cs b/src/Numerics/LinearAlgebra/Storage/VectorStorage.cs
index 88a62bb7..913e72ab 100644
--- a/src/Numerics/LinearAlgebra/Storage/VectorStorage.cs
+++ b/src/Numerics/LinearAlgebra/Storage/VectorStorage.cs
@@ -374,6 +374,23 @@ namespace MathNet.Numerics.LinearAlgebra.Storage
             }
         }
 
+        // EXTRACT
+
+        public virtual T[] ToArray()
+        {
+            var ret = new T[Length];
+            for (int i = 0; i < ret.Length; i++)
+            {
+                ret[i] = At(i);
+            }
+            return ret;
+        }
+
+        public virtual T[] AsArray()
+        {
+            return null;
+        }
+
         // ENUMERATION
 
         public virtual IEnumerable<T> Enumerate()
diff --git a/src/Numerics/LinearAlgebra/Vector.cs b/src/Numerics/LinearAlgebra/Vector.cs
index b76b4bfc..b7a4b780 100644
--- a/src/Numerics/LinearAlgebra/Vector.cs
+++ b/src/Numerics/LinearAlgebra/Vector.cs
@@ -238,15 +238,23 @@ namespace MathNet.Numerics.LinearAlgebra
 
         /// <summary>
         /// Returns the data contained in the vector as an array.
+        /// The returned array will be independent from this vector.
+        /// A new memory block will be allocated for the array.
         /// </summary>
-        /// <returns>
-        /// The vector's data as an array.
-        /// </returns>
+        /// <returns>The vector's data as an array.</returns>
         public T[] ToArray()
         {
-            var result = new DenseVectorStorage<T>(Count);
-            Storage.CopyToUnchecked(result, ExistingData.AssumeZeros);
-            return result.Data;
+            return Storage.ToArray();
+        }
+
+        /// <summary>
+        /// Returns the internal array of this vector if, and only if, this vector is stored by such an array internally.
+        /// Otherwise returns null. Changes to the returned array and the vector will affect each other.
+        /// Use ToArray instead if you always need an independent array.
+        /// </summary>
+        public T[] AsArray()
+        {
+            return Storage.AsArray();
         }
 
         /// <summary>