naive-mm-c++.cpp

void multiply1D(Matrix1D *A, Matrix1D *B, Matrix1D *C, int n) {
    for (int i = 0; i < n; ++i) {
        double *Arow = &A->matrix[i * n];
        double *Crow = &C->matrix[i * n];

        for (int j = 0; j < n; ++j) {
            double sum = 0;

            for (int k = 0; k < n; ++k)
                sum += *(Arow + k) * B->matrix[k * n + j];

            *(Crow + j) = sum;
        }
    }
}