diff --git a/testers/prefactor_code.c b/testers/prefactor_code.c
new file mode 100644
index 0000000..cbacecd
--- /dev/null
+++ b/testers/prefactor_code.c
@@ -0,0 +1,38 @@
+//
+// Created by anapt on 18/1/2018.
+//
+
+// compute kernel matrix
+//        // apply function to non zero elements of a sparse matrix
+//        for (int i=0; i<ROWS; i++){
+//            for (int j=0; j<ROWS; j++){
+//                if (W[i][j] != 0){
+//                    double pow = ((-1)*(W[i][j]))/(2*(h*h));
+//                    W[i][j] = exp(pow);
+//                }
+//            }
+//        }
+
+//        // make sure diagonal elements are 1
+//        for (int i=0; i<ROWS; i++){
+//            for (int j=0; j<ROWS; j++){
+//                if (i==j){
+//                    W[i][j] = W[i][j] +1;
+//                }
+//            }
+//        }
+
+
+//        // normalize vector
+//        // allocate memory for vector l [600 1]
+//        double * l = malloc(ROWS * sizeof(double));
+//        // calculate sum(W,2)
+
+//        // W is a 600 by 600 sparse matrix
+//        for (int i=0; i<ROWS; i++){
+//            double sum =0;
+//            for (int j = 0; j < ROWS; j++){
+//                sum = sum + W[i][j];
+//            }
+//            l[i] = sum;
+//        }
\ No newline at end of file
diff --git a/testers/test_code.c b/testers/test_code.c
new file mode 100644
index 0000000..0f39a70
--- /dev/null
+++ b/testers/test_code.c
@@ -0,0 +1,114 @@
+//
+// Created by anapt on 17/1/2018.
+//
+
+#include<stdio.h>
+#include<math.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <float.h>
+#include <stdbool.h>
+#define X "data/X.bin"
+#define Y "data/X.bin"
+#define COLUMNS     2
+#define ROWS        6
+#define N           4
+
+
+// allocates a 2d array in continuous memory positions
+double **alloc_2d_double(int rows, int cols) {
+    double *data = (double *)malloc(rows*cols*sizeof(double));
+    double **array= (double **)malloc(rows*sizeof(double*));
+    for (int i=0; i<rows; i++)
+        array[i] = &(data[cols*i]);
+    return array;
+}
+
+// copy the values of a 2d double array to another
+double **duplicate(double **a, double **b, int rows, int cols){
+    for (int i=0;i<rows;i++){
+        for (int j=0;j<cols;j++){
+            b[i][j] = a[i][j];
+        }
+    }
+    return b;
+}
+
+// TODO check why there's is a difference in the norm calculate in matlab
+
+double norm(double ** m, int rows, int cols){
+    double sum=0, a=0;
+    for (int i = 0; i < rows; i++) {
+        for (int j = 0; j < cols; j++) {
+            a = m[i][j] * m[i][j];
+            sum = sum + a;
+        }
+    }
+    double norm = sqrt(sum);
+    return norm;
+}
+
+double norm2(double ** m, int rows, int cols){
+    double sum=0, a=0;
+    for (int i = 0; i < cols; i++) {
+        for (int j = 0; j < rows; j++) {
+            a = m[i][j] * m[i][j];
+            sum = sum + a;
+        }
+    }
+    double norm = sqrt(sum);
+    return norm;
+}
+
+void multiply(double ** matrix1, double ** matrix2, double ** output){
+    // W dims are ROWS ROWS and x dims are ROWS COLUMNS
+    // TODO IMPLEMENT
+    int i, j, k;
+    for (i=0; i<ROWS; i++){
+        for (j=0; j<COLUMNS; j++){
+            output[i][j] = 0;
+            for (k=0; k<ROWS; k++){
+                output[i][j] += matrix1[i][k] * matrix2[k][j];
+            }
+        }
+    }
+}
+
+void print_matrix(double ** array, int rows, int cols){
+    for (int i=0; i<rows; i++){
+        for (int j=0; j<cols; j++){
+            printf("%f ", array[i][j]);
+        }
+        printf("\n");
+    }
+}
+
+int main()
+{
+
+    double ** vector1, **vector2, **res;
+//    printf("norm : %f \n", norm(vectors, ROWS, COLUMNS));
+//    printf("norm : %f \n", norm2(vectors, ROWS, COLUMNS));
+
+    FILE *f;
+    f = fopen(X, "rb");
+    vector1 = alloc_2d_double(ROWS, ROWS);
+    for (int i=0; i<ROWS; i++){
+        int out = fread(vector1[i], sizeof(double), ROWS, f);
+    }
+    fclose(f);
+    FILE *f2;
+    f2 = fopen(Y, "rb");
+    vector2 = alloc_2d_double(ROWS, COLUMNS);
+    for (int i=0; i<ROWS; i++){
+        int out = fread(vector2[i], sizeof(double), COLUMNS, f2);
+    }
+    fclose(f2);
+    res = alloc_2d_double(ROWS, COLUMNS);
+    multiply(vector1, vector2, res);
+    print_matrix(vector1, ROWS, ROWS);
+    print_matrix(vector2, ROWS, COLUMNS);
+    print_matrix(res, ROWS, COLUMNS);
+    return 0;
+}
+