From 76494aa44bcff04ebadc449accc6c3feba1d573e Mon Sep 17 00:00:00 2001
From: Arthur <Arthur@KLPD>
Date: Fri, 24 Jun 2016 17:49:31 +0200
Subject: [PATCH] Directly address underlying data-array for multiplying sparse
 with dense matrices with DenseColumnMajorMatrixStorage

---
 .../LinearAlgebra/Double/SparseMatrix.cs      | 32 +++++++++++++++++--
 .../LinearAlgebra/Single/SparseMatrix.cs      | 31 ++++++++++++++++--
 2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/src/Numerics/LinearAlgebra/Double/SparseMatrix.cs b/src/Numerics/LinearAlgebra/Double/SparseMatrix.cs
index 05932563..d332005d 100644
--- a/src/Numerics/LinearAlgebra/Double/SparseMatrix.cs
+++ b/src/Numerics/LinearAlgebra/Double/SparseMatrix.cs
@@ -906,12 +906,40 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             }
 
             result.Clear();
-            var columnVector = new DenseVector(other.RowCount);
-
             var rowPointers = _storage.RowPointers;
             var columnIndices = _storage.ColumnIndices;
             var values = _storage.Values;
 
+            var denseOther = other.Storage as DenseColumnMajorMatrixStorage<double>;
+            if (denseOther != null)
+            {
+                // in this case we can directly address the underlying data-array
+                for (var row = 0; row < RowCount; row++)
+                {
+                    var startIndex = rowPointers[row];
+                    var endIndex = rowPointers[row + 1];
+
+                    if (startIndex == endIndex)
+                    {
+                        continue;
+                    }
+
+                    for (var column = 0; column < other.ColumnCount; column++)
+                    {
+                        int otherColumnStartPosition = column * other.RowCount;
+                        var sum = 0d;
+                        for (var index = startIndex; index < endIndex; index++)
+                        {
+                            sum += values[index] * denseOther.Data[otherColumnStartPosition + columnIndices[index]];
+                        }
+
+                        result.At(row, column, sum);
+                    }
+                }
+                return;
+            }
+
+            var columnVector = new DenseVector(other.RowCount);
             for (var row = 0; row < RowCount; row++)
             {
                 var startIndex = rowPointers[row];
diff --git a/src/Numerics/LinearAlgebra/Single/SparseMatrix.cs b/src/Numerics/LinearAlgebra/Single/SparseMatrix.cs
index 38fb42c3..15d30bae 100644
--- a/src/Numerics/LinearAlgebra/Single/SparseMatrix.cs
+++ b/src/Numerics/LinearAlgebra/Single/SparseMatrix.cs
@@ -909,12 +909,39 @@ namespace MathNet.Numerics.LinearAlgebra.Single
             }
 
             result.Clear();
-            var columnVector = new DenseVector(other.RowCount);
-
             var rowPointers = _storage.RowPointers;
             var columnIndices = _storage.ColumnIndices;
             var values = _storage.Values;
+            var denseOther = other.Storage as DenseColumnMajorMatrixStorage<float>;
+            if (denseOther != null)
+            {
+                // in this case we can directly address the underlying data-array
+                for (var row = 0; row < RowCount; row++)
+                {
+                    var startIndex = rowPointers[row];
+                    var endIndex = rowPointers[row + 1];
 
+                    if (startIndex == endIndex)
+                    {
+                        continue;
+                    }
+
+                    for (var column = 0; column < other.ColumnCount; column++)
+                    {
+                        int otherColumnStartPosition = column * other.RowCount;
+                        var sum = 0f;
+                        for (var index = startIndex; index < endIndex; index++)
+                        {
+                            sum += values[index] * denseOther.Data[otherColumnStartPosition + columnIndices[index]];
+                        }
+
+                        result.At(row, column, sum);
+                    }
+                }
+                return;
+            }
+
+            var columnVector = new DenseVector(other.RowCount);
             for (var row = 0; row < RowCount; row++)
             {
                 var startIndex = rowPointers[row];