From 5fddebd1bc9e0a82579abc9cd5d7183727e355fa Mon Sep 17 00:00:00 2001
From: Pascal Serrarens <pse@pale.blue>
Date: Wed, 9 Apr 2025 12:31:46 +0200
Subject: [PATCH] Performance improvements

---
 LinearAlgebra/Matrix.cpp | 44 ++++++++++++++++++++++++++--------------
 LinearAlgebra/Matrix.h   |  1 +
 2 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/LinearAlgebra/Matrix.cpp b/LinearAlgebra/Matrix.cpp
index c18ce3a..fae5c6a 100644
--- a/LinearAlgebra/Matrix.cpp
+++ b/LinearAlgebra/Matrix.cpp
@@ -3,7 +3,7 @@
 
 namespace LinearAlgebra {
 
-  #pragma region Matrix1
+#pragma region Matrix1
 
 Matrix1::Matrix1(int size) : size(size) {
   if (this->size == 0)
@@ -97,6 +97,11 @@ Matrix2 Matrix2::Zero(int nRows, int nCols) {
   return r;
 }
 
+void Matrix2::Clear() {
+  for (int ix = 0; ix < this->nValues; ix++)
+    this->data[ix] = 0;
+}
+
 Matrix2 Matrix2::Identity(int size) {
   return Diagonal(1, size);
 }
@@ -129,7 +134,8 @@ Matrix2 Matrix2::Transpose() const {
 
   for (uint rowIx = 0; rowIx < this->nRows; rowIx++) {
     for (uint colIx = 0; colIx < this->nCols; colIx++)
-      r.data[colIx * this->nCols + rowIx] = this->data[rowIx * this->nCols + colIx];
+      r.data[colIx * this->nCols + rowIx] =
+          this->data[rowIx * this->nCols + colIx];
   }
   return r;
 }
@@ -177,10 +183,7 @@ Matrix2 LinearAlgebra::Matrix2::operator*(const Matrix2& B) const {
   return r;
 }
 
-Matrix2 Matrix2::Slice(int rowStart,
-                          int rowStop,
-                          int colStart,
-                          int colStop) {
+Matrix2 Matrix2::Slice(int rowStart, int rowStop, int colStart, int colStop) {
   Matrix2 r = Matrix2(rowStop - rowStart, colStop - colStart);
 
   int resultRowIx = 0;
@@ -194,14 +197,25 @@ Matrix2 Matrix2::Slice(int rowStart,
 }
 
 void Matrix2::UpdateSlice(int rowStart,
-                                      int rowStop,
-                                      int colStart,
-                                      int colStop,
-                                      const Matrix2& m) const {
-  for (int i = rowStart; i < rowStop; i++) {
-    for (int j = colStart; j < colStop; j++)
-      this->data[i * this->nCols + j] =
-          m.data[(i - rowStart) * m.nCols + (j - colStart)];
+                          int rowStop,
+                          int colStart,
+                          int colStop,
+                          const Matrix2& m) const {
+  // for (int i = rowStart; i < rowStop; i++) {
+  //   for (int j = colStart; j < colStop; j++)
+  //     this->data[i * this->nCols + j] =
+  //         m.data[(i - rowStart) * m.nCols + (j - colStart)];
+  // }
+
+  int rRowDataIx = rowStart * this->nCols;
+  int mRowDataIx = 0;
+  for (int rowIx = rowStart; rowIx < rowStop; rowIx++) {
+    rRowDataIx = rowIx * this->nCols;
+    // rRowDataIx += this->nCols;
+    mRowDataIx += m.nCols;
+    for (int colIx = colStart; colIx < colStop; colIx++) {
+      this->data[rRowDataIx + colIx] = m.data[mRowDataIx + (colIx - colStart)];
+    }
   }
 }
 
@@ -229,7 +243,7 @@ Matrix2 LinearAlgebra::Matrix2::Omega(const Vector3& v) {
 // Matrix2
 #pragma endregion
 
-}  // namespace LinearAlgbra
+}  // namespace LinearAlgebra
 
 template <>
 MatrixOf<float>::MatrixOf(unsigned int rows, unsigned int cols) {
diff --git a/LinearAlgebra/Matrix.h b/LinearAlgebra/Matrix.h
index 65d55d0..fc40055 100644
--- a/LinearAlgebra/Matrix.h
+++ b/LinearAlgebra/Matrix.h
@@ -39,6 +39,7 @@ class Matrix2 {
   Matrix2 Clone() const;
 
   static Matrix2 Zero(int nRows, int nCols);
+  void Clear();
 
   static Matrix2 Identity(int size);