From 8b76d014c1d682098fa13d7f25538bba799bd87f Mon Sep 17 00:00:00 2001
From: Simon Wiesend <117300309+smnws@users.noreply.github.com>
Date: Sun, 9 Nov 2025 13:25:47 +0100
Subject: [PATCH] This implements all functions in matrix.c except multiply().
 All tests from matrixTests.c are passing for the implemented functions.

---
 .gitignore |  3 ++-
 matrix.c   | 68 ++++++++++++++++++++++++++++++++++++++++++++++--------
 matrix.h   |  9 ++++++--
 3 files changed, 68 insertions(+), 12 deletions(-)

diff --git a/.gitignore b/.gitignore
index 4f907f8..39be31d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 mnist
 runTests
 *.o
-*.exe
\ No newline at end of file
+*.exe
+runMatrixTests
\ No newline at end of file
diff --git a/matrix.c b/matrix.c
index ad00628..917a8b2 100644
--- a/matrix.c
+++ b/matrix.c
@@ -2,34 +2,84 @@
 #include <string.h>
 #include "matrix.h"
 
-// TODO Matrix-Funktionen implementieren
-
 Matrix createMatrix(unsigned int rows, unsigned int cols)
 {
-    
+    Matrix mat = {.rows = rows, .cols = cols};
+    // If one dimension is 0, return both dimensions as 0 and don't init the array/buffer.
+    if (rows == 0 || cols == 0)
+    {
+        mat.rows = 0;
+        mat.cols = 0;
+        return mat;
+    }
+
+    // allocate contiguous and 0 initialized memory
+    mat.buffer = calloc(rows * cols, sizeof(MatrixType));
+
+    // check if calloc failed
+    if (mat.buffer == NULL)
+    {
+        clearMatrix(&mat);
+    }
+
+    return mat;
 }
 
+// reduce the dimensions to (0, 0) and free the memory
 void clearMatrix(Matrix *matrix)
 {
-    
+    free(matrix->buffer);
+    matrix->buffer = NULL;
+    matrix->cols = 0;
+    matrix->rows = 0;
 }
 
 void setMatrixAt(MatrixType value, Matrix matrix, unsigned int rowIdx, unsigned int colIdx)
 {
-    
+    // do nothing if idx is not in array or matrix buffer is NULL
+    if (!(rowIdx < matrix.rows) || !(colIdx < matrix.cols) || matrix.buffer == NULL)
+    {
+        return;
+    }
+
+    matrix.buffer[rowIdx * matrix.cols + colIdx] = value;
 }
 
 MatrixType getMatrixAt(const Matrix matrix, unsigned int rowIdx, unsigned int colIdx)
 {
-    
-}
+    // return UNDEFINED_MATRIX_VALUE if idx is not in array or matrix buffer is NULL
+    if (!(rowIdx < matrix.rows) || !(colIdx < matrix.cols) || matrix.buffer == NULL)
+    {
+        return UNDEFINED_MATRIX_VALUE;
+    }
+
+    return matrix.buffer[rowIdx * matrix.cols + colIdx];
+};
 
 Matrix add(const Matrix matrix1, const Matrix matrix2)
 {
-    
+    Matrix resMat = createMatrix(matrix1.rows, matrix1.cols);
+
+    // clear matrix and return if the dimensions of the input matrices differ from each other
+    if (matrix1.rows != matrix2.rows || matrix1.cols != matrix2.cols)
+    {
+        clearMatrix(&resMat);
+        return resMat;
+    }
+
+    for (size_t m = 0; m < matrix1.rows; m++)
+    {
+        for (size_t n = 0; n < matrix1.cols; n++)
+        {
+            // this is unnecessarily complicated because at this point we already know that the matrices are compatible
+            setMatrixAt(getMatrixAt(matrix1, m, n) + getMatrixAt(matrix2, m, n), resMat, m, n);
+        }
+    }
+
+    return resMat;
 }
 
+// TODO implement
 Matrix multiply(const Matrix matrix1, const Matrix matrix2)
 {
-    
 }
\ No newline at end of file
diff --git a/matrix.h b/matrix.h
index cc640d1..9293cb6 100644
--- a/matrix.h
+++ b/matrix.h
@@ -5,8 +5,14 @@
 
 typedef float MatrixType;
 
-// TODO Matrixtyp definieren
+// Matrixtyp
+typedef struct Matrix
+{
+    size_t rows;
+    size_t cols;
+    MatrixType *buffer;
 
+} Matrix;
 
 Matrix createMatrix(unsigned int rows, unsigned int cols);
 void clearMatrix(Matrix *matrix);
@@ -15,5 +21,4 @@ MatrixType getMatrixAt(const Matrix matrix, unsigned int rowIdx, unsigned int co
 Matrix add(const Matrix matrix1, const Matrix matrix2);
 Matrix multiply(const Matrix matrix1, const Matrix matrix2);
 
-
 #endif