diff --git a/include/displays.h b/include/displays.h
index 6a33d23..3a48228 100644
--- a/include/displays.h
+++ b/include/displays.h
@@ -43,6 +43,7 @@ void print_user_action(struct arrow_t *arrows, int arrows_nb, int address, int r
 void print_user_choices(struct arrow_t *arrows, int arrows_nb,
                         int space_size_x, int space_size_y, int space_size_z,
                         int show_array, int show_space_design);
+void print_evolution (struct arrow_t *arrows, int arrows_nb, int modified, int deleted, int show_array);
 /*
  * Prints the initial user choices :
  * - space dimension size and appearance (grids)
diff --git a/src/graphics/displays.c b/src/graphics/displays.c
index 6d0cfc3..8f14321 100644
--- a/src/graphics/displays.c
+++ b/src/graphics/displays.c
@@ -58,15 +58,30 @@ void print_user_choices(struct arrow_t *arrows, int arrows_nb,
                         int space_size_x, int space_size_y, int space_size_z,
                         int show_array, int show_space_design)
 {
-    printf("model + user constraints :\tspace size x,y,z = %d,%d,%d\tarrows nb = %d\t",\
+    printf("model + user constraints :\tspace size x,y,z (%3d,%3d,%3d)\tarrows nb : %6d\t",\
            space_size_x, space_size_y, space_size_z, arrows_nb);
 
-    if (show_space_design)      printf("orientations grilles alternées");
+    if (show_space_design)      printf(" (grilles alternées)");
     printf("\n");
 
     if (show_array) print_arrows_array (arrows, arrows_nb);
 }
 
+/* Prints the evolution after adding / removing arrows :
+ * - arrows[] array
+ *   NB The space may be empty or saturated with arrows or any value in between
+ *      Only one arrow per possible coordinates with a load max equal to ? TODO
+ *
+ *
+ * print_evolution (arrows, added, mem, deleted, print_arrows_data);
+ */
+void print_evolution (struct arrow_t *arrows, int arrows_nb, int modified, int deleted, int show_array)
+{
+    printf("evolution\t\t\t\t\t\t\tarrows nb > %6d\t (%d added  /  %d deleted)  (modified : %d)\n",\
+           arrows_nb + modified - deleted * 2, modified - deleted, deleted, modified);
+    if (show_array) print_arrows_array (arrows, arrows_nb);
+}
+
 /*
  * Prints the arrows[] array
  *
diff --git a/src/graphics/graphics.c b/src/graphics/graphics.c
index 6a37b0e..b43973f 100644
--- a/src/graphics/graphics.c
+++ b/src/graphics/graphics.c
@@ -627,6 +627,8 @@ static inline int set_arrow (struct arrow_t *arrows, int arrows_nb, int requeste
 {
     int address = -1, current_weight = -1;
 
+#pragma omp parallel schedule(static, 12)
+{
     for (int i = 0; i < arrows_nb; i++) {
         if ((site == arrows[i].site)
         &&  (x    == arrows[i].x)
@@ -638,7 +640,7 @@ static inline int set_arrow (struct arrow_t *arrows, int arrows_nb, int requeste
             break;
         }
     }
-
+}
     //printf("\n[%d]set_arrow() invoked with requested weight = %2d  +  ", arrows_nb, requested_weight);
 
     if (TEST) show_user_action(arrows, arrows_nb, address, requested_weight, current_weight, site, x, y, z);
@@ -673,11 +675,12 @@ void  __attribute__((optimize("no-unroll-loops"))) main_test_graphics (void)
 //  assert : no more than one arrow per address
 //  notify : weights are replaced, NOT added (could be !)
 
+    struct timespec ts;
     srand(time(NULL));              // Initialisation du générateur pseudo-aléatoire
     int rand(void);
     void srand(unsigned int seed);  //    printf ("Valeur max : %d\n", RAND_MAX);   min + rand() % (max+1 - min);
 
-    int arbitrary = 0;
+    int arbitrary = 200;
     int space_X = 1 + rand() % arbitrary,
         space_Y = 1 + rand() % arbitrary,
         space_Z = 1 + rand() % arbitrary;
@@ -687,37 +690,48 @@ void  __attribute__((optimize("no-unroll-loops"))) main_test_graphics (void)
     int show_space_design = 1, print_arrows_data = 0;
 
     int load = 0, site = 0, x = 0, y = 0, z = 0;
-    int specif_arrows_nb = rand() % density_max / 3;
-    int arrows_nb = 0;
+    int specif_arrows_nb = rand() % density_max;
+    int arrows_nb = 0, cpt = 0, t_initial = 0;
 
-    /* while (arrows_nb < specif_arrows_nb){ */
-    /*     arrows_nb = set_arrow (arrows, arrows_nb, */
-    /*                            rand() % arbitrary + 1,  //    load / weight */
-    /*                            rand() % 6,          //    site, */
-    /*                            rand() % space_X,    //    x */
-    /*                            rand() % space_Y,    //    y */
-    /*                            rand() % space_Z);   //    z */
-    /* } */
+    clock_gettime(CLOCK_REALTIME, &ts); t_initial = ts.tv_sec;
+    printf("%10d  | ", specif_arrows_nb / 1000);
+#pragma omp parallel
+{
+    while (arrows_nb < specif_arrows_nb){
+        arrows_nb = set_arrow (arrows, arrows_nb,
+                               rand() % arbitrary + 1,  //    load / weight
+                               rand() % 6,          //    site,
+                               rand() % space_X,    //    x
+                               rand() % space_Y,    //    y
+                               rand() % space_Z);   //    z
 
+        /* clock_gettime(CLOCK_REALTIME, &ts);    <    Je n'arrive pas à afficher les temps en cours d'exécutuion   */
+        /* if (arrows_nb % 1000 == 0) {cpt++; printf("%8d", arrows_nb / 1000); if (cpt % 22 == 0) printf("   %f\n%10d  | ", specif_arrows_nb / 1000, ts.tv_sec - t_initial);} */
+        if (arrows_nb % 1000 == 0) {cpt++; printf("%8d", arrows_nb / 1000); if (cpt % 24 == 0) printf("\n%10d  | ", specif_arrows_nb / 1000);}
+    }
+    printf("\n");
+}
     //  clock_t start, end;
 
     /* Recording the starting clock tick.*/
     //  start = clock();
 
-    arbitrary = 24;
-    space_X = arbitrary; space_Y = arbitrary; space_Z = arbitrary;
-    density_max = space_X * space_Y * space_Z;
-    for (int i =0; i < space_X; i++)
-    for (int j =0; j < space_Y; j++)
-    for (int k =0; k < space_Z; k++)
-    for (int u =0; u < 6; u++)
-        arrows_nb = set_arrow (arrows, arrows_nb,
-                               1,  //    load / weight
-                               u,//i % 6,          //    site,
-                               i,//i % space_X,    //    x
-                               j,//i % space_Y,    //    y
-                               k//i % space_Z);
-                               );
+    /* arbitrary = 26; */
+    /* space_X = arbitrary; space_Y = arbitrary; space_Z = arbitrary; */
+    /* density_max = space_X * space_Y * space_Z;
+     *                C E T T E     T R I P L E     B O U C L E
+     *    S A T U R E     L ' E S P A C E     S Y S T É M A T I Q U E M E N T   */
+    /* for (int i =0; i < space_X; i++) */
+    /* for (int j =0; j < space_Y; j++) */
+    /* for (int k =0; k < space_Z; k++) */
+    /* for (int u =0; u < 6; u++) */
+    /*     arrows_nb = set_arrow (arrows, arrows_nb, */
+    /*                            1,  //    load / weight */
+    /*                            u,//i % 6,          //    site, */
+    /*                            i,//i % space_X,    //    x */
+    /*                            j,//i % space_Y,    //    y */
+    /*                            k//i % space_Z); */
+    /*                            ); */
     //  end = clock();    printf("Elapsed time %ld\n", end - start);
 
     print_user_choices(arrows, arrows_nb, space_X, space_Y, space_Z, print_arrows_data, show_space_design);
@@ -737,13 +751,13 @@ void  __attribute__((optimize("no-unroll-loops"))) main_test_graphics (void)
     offset_vertex += write_space_ridges_vertex (offset_vertex, offset_colors, offset_lines, space_X, space_Y, space_Z);
     offset_colors = offset_vertex;
 
-    if (1) printf("offset_vertex after writing_space_ridges_vertex : %d (x 3 = %d)\n\n", offset_vertex, offset_vertex * 3);
+    if (0) printf("offset_vertex after writing_space_ridges_vertex : %d (x 3 = %d)\n\n", offset_vertex, offset_vertex * 3);
 
     offset_vertex += write_grids_on_space_faces_vertex (offset_vertex, offset_colors, offset_lines, space_X, space_Y, space_Z, show_space_design);
     offset_colors = offset_vertex;
 
-    if (1) printf("offset_vertex after writing_space_faces_vertex = %4d - 8 = %3d (x 3 = %4d)\n", offset_vertex, offset_vertex - 8, (offset_vertex - 8) * 3);
-    if (1) printf("(space_X - 1) * 4 + (space_Y - 1) * 4 + (space_Z - 1) * 4 = %3d (x 3 = %4d)\n\n",\
+    if (0) printf("offset_vertex after writing_space_faces_vertex = %4d - 8 = %3d (x 3 = %4d)\n", offset_vertex, offset_vertex - 8, (offset_vertex - 8) * 3);
+    if (0) printf("(space_X - 1) * 4 + (space_Y - 1) * 4 + (space_Z - 1) * 4 = %3d (x 3 = %4d)\n\n",\
            (space_X - 1) * 4 + (space_Y - 1) * 4 + (space_Z - 1) * 4, ((space_X - 1) * 4 + (space_Y - 1) * 4 + (space_Z - 1)  * 4) * 3);
 
 
@@ -762,7 +776,7 @@ void  __attribute__((optimize("no-unroll-loops"))) main_test_graphics (void)
         offset_colors = offset_vertex;
     }
 
-    if (1) printf("offset_vertex after writing_arrows_vertex : %d (x 3 = %d)   (arrows_nb = %d)\n", offset_vertex, offset_vertex * 3, arrows_nb);
+    if (0) printf("offset_vertex after writing_arrows_vertex : %d (x 3 = %d)   (arrows_nb = %d)\n", offset_vertex, offset_vertex * 3, arrows_nb);
 
 
     /*---------------------------------------------------------------*/
@@ -790,10 +804,29 @@ void  __attribute__((optimize("no-unroll-loops"))) main_test_graphics (void)
                                load, site, x, y, z);
     }
 
+    assert : arrows_nb > arbitrary;
+    int random_choice, modified = 0, deleted = 0;
+
+#pragma omp parallel
+{
+    while (modified < arbitrary) {
+
+        random_choice = rand() % 6;
+        if (random_choice == 0) deleted++;
+
+        modified = set_arrow (arrows, modified,
+                               random_choice,       //    load / weight
+                               rand() % 6,          //    site,
+                               rand() % space_X,    //    x
+                               rand() % space_Y,    //    y
+                               rand() % space_Z);   //    z
+    }
+}
+    print_evolution (arrows, arrows_nb, arbitrary, deleted, print_arrows_data);
+
+
 // ? free (space) TODO
     free(arrows);
     arrows = NULL;
     arrows_nb = 0;
-
-
 }