Fixed design of the matrix methods.

src/Numerics/LinearAlgebra/Double/DenseMatrix.cs

@@ -198,6 +198,25 @@ namespace MathNet.Numerics.LinearAlgebra.Double
         /// <exception cref="ArgumentNullException">If the other matrix is <see langword="null" />.</exception>
         /// <exception cref="ArgumentOutOfRangeException">If the two matrices don't have the same dimensions.</exception>
         public override void Add(Matrix other)
+        {
+            DenseMatrix m = other as DenseMatrix;
+            if (m == null)
+            {
+                base.Add(other);
+            }
+            else
+            {
+                Add(other);
+            }
+        }
+
+        /// <summary>
+        /// Adds another <see cref="DenseMatrix"/> to this matrix. The result will be written into this matrix.
+        /// </summary>
+        /// <param name="other">The <see cref="DenseMatrix"/> to add to this matrix.</param>
+        /// <exception cref="ArgumentNullException">If the other matrix is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentOutOfRangeException">If the two matrices don't have the same dimensions.</exception>
+        public void Add(DenseMatrix other)
         {
             if (other == null)
             {
@@ -209,26 +228,35 @@ namespace MathNet.Numerics.LinearAlgebra.Double
                 throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixSameDimensions);
             }
 
+            Control.LinearAlgebraProvider.AddArrays(Data, other.Data, Data);
+        }
+
+        /// <summary>
+        /// Subtracts another matrix from this matrix. The result will be written into this matrix.
+        /// </summary>
+        /// <param name="other">The matrix to subtract.</param>
+        /// <exception cref="ArgumentNullException">If the other matrix is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentOutOfRangeException">If the two matrices don't have the same dimensions.</exception>
+        public override void Subtract(Matrix other)
+        {
             DenseMatrix m = other as DenseMatrix;
             if (m == null)
             {
-                Parallel.For(0, RowCount, i =>
-                    Parallel.For(0, ColumnCount, j =>
-                        At(i, j, At(i, j) + other.At(i, j))));
+                base.Subtract(other);
             }
             else
             {
-                Control.LinearAlgebraProvider.AddArrays(Data, m.Data, Data);
+                Subtract(m);
             }
         }
 
         /// <summary>
-        /// Subtracts another matrix from this matrix. The result will be written into this matrix.
+        /// Subtracts another <see cref="DenseMatrix"/> from this matrix. The result will be written into this matrix.
         /// </summary>
-        /// <param name="other">The matrix to subtract.</param>
+        /// <param name="other">The <see cref="DenseMatrix"/> to subtract.</param>
         /// <exception cref="ArgumentNullException">If the other matrix is <see langword="null" />.</exception>
         /// <exception cref="ArgumentOutOfRangeException">If the two matrices don't have the same dimensions.</exception>
-        public override void Subtract(Matrix other)
+        public void Subtract(DenseMatrix other)
         {
             if (other == null)
             {
@@ -239,18 +267,8 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             {
                 throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixSameDimensions);
             }
-
-            DenseMatrix m = other as DenseMatrix;
-            if (m == null)
-            {
-                Parallel.For(0, RowCount, i =>
-                    Parallel.For(0, ColumnCount, j =>
-                        At(i, j, At(i, j) - other.At(i, j))));
-            }
-            else
-            {
-                Control.LinearAlgebraProvider.SubtractArrays(Data, m.Data, Data);
-            }
+            
+            Control.LinearAlgebraProvider.SubtractArrays(Data, other.Data, Data);
         }
         #endregion
     }

src/Numerics/LinearAlgebra/Double/Matrix.cs

@@ -446,9 +446,13 @@ namespace MathNet.Numerics.LinearAlgebra.Double
                 throw new ArgumentOutOfRangeException(Resources.ArgumentMatrixSameDimensions);
             }
 
-            Parallel.For(0, RowCount, i => 
-                Parallel.For(0, ColumnCount, j =>
-                    At(i, j, At(i,j) + other.At(i,j))));
+            Parallel.For(0, RowCount, i =>
+            {
+                for (int j = 0; j < ColumnCount; j++)
+                {
+                    At(i, j, At(i, j) + other.At(i, j));
+                }
+            });
         }
 
         /// <summary>
@@ -502,8 +506,12 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             }
 
             Parallel.For(0, RowCount, i =>
-                Parallel.For(0, ColumnCount, j =>
-                    At(i, j, At(i, j) - other.At(i, j))));
+            {
+                for(int j = 0; j < ColumnCount; j++)
+                {
+                    At(i, j, At(i, j) - other.At(i, j));
+                }
+            });
         }
 
         /// <summary>