Multidimensionale Array-Zeiger-Flattenung und optimierter Schrittweiten-Zugriff

#include <stdio.h>
#include <stdlib.h>
 
/* Linearized 2D grid allocation for single-heap allocation and cache prefetching */
typedef struct {
    size_t rows;
    size_t cols;
    double data[];
} Matrix;
 
Matrix* allocate_matrix(size_t rows, size_t cols) {
    Matrix *m = malloc(sizeof(Matrix) + sizeof(double) * rows * cols);
    if (!m) return NULL;
    m->rows = rows;
    m->cols = cols;
    return m;
}
 
inline static double get_element(const Matrix *m, size_t r, size_t c) {
    /* Strided access calculation: index = row * cols + col */
    return m->data[r * m->cols + c];
}
 
int main(void) {
    Matrix *m = allocate_matrix(4, 4);
    if (m) {
        m->data[2 * 4 + 3] = 42.5; /* Row 2, Col 3 */
        printf("Value at (2,3): %.1f\n", get_element(m, 2, 3));
        free(m);
    }
    return 0;
}