diff --git a/Makefile b/Makefile
index b70e681..6a7c510 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@ SRCDIR=src
 DEBDIR=debian
 SERVEROBJ=	$(BINDIR)/scheduler.o $(BINDIR)/server.o $(BINDIR)/localworker.o \
 		$(BINDIR)/centers.o $(BINDIR)/cmds.o $(BINDIR)/model.o \
-		$(BINDIR)/main.o
+		$(BINDIR)/main.o $(BINDIR)/arrows.o
 CLIOBJ=		$(BINDIR)/cli.o
 
 .DEFAULT_GOAL:= all
diff --git a/include/base.h b/include/base.h
index ae7a8d5..ee5acda 100644
--- a/include/base.h
+++ b/include/base.h
@@ -45,7 +45,7 @@ struct {
 
 struct {
     size_t size;
-    bool lock;
+    pthread_spinlock_t lock;
     Arrow_t *array;
 } typedef ArrowArray_t;
 
@@ -81,7 +81,7 @@ struct {
 struct {
     Space_t *globalDrawingSpace;
     IntArray_t *transitionsTree;
-    ArrowArray_t *arrowList;
+    ArrowArray_t *arrowArray;
     int nmaxThread;
     int nmaxCycles;
     int ruleRadius;
@@ -108,7 +108,7 @@ struct {
     Center_t *localWorkAreaCenter;
     Space_t *globalDrawingSpace;
     IntArray_t *transitionsTree;
-    ArrowArray_t *arrowList;
+    ArrowArray_t *arrowArray;
     bool pleaseStop;
     bool terminated;
     int returnValue;
diff --git a/include/model.h b/include/model.h
index 4256da6..f63decc 100644
--- a/include/model.h
+++ b/include/model.h
@@ -24,3 +24,8 @@
 #endif
 
 void ModelPrepareSpace(Space_t *globalDrawingSpace, Model_t *model);
+
+void ModelPrepareArrows(Space_t *globalDrawingSpace, ArrowArray_t *arrowList,
+                        Model_t *model);
+
+
diff --git a/include/scheduler.h b/include/scheduler.h
index 573a81f..cb5eb40 100644
--- a/include/scheduler.h
+++ b/include/scheduler.h
@@ -37,8 +37,8 @@ static inline void SchedDestroy(Scheduler_t *scheduler)
     free(scheduler->globalDrawingSpace->space);
     free(scheduler->globalDrawingSpace);
 
-    free(scheduler->arrowList->array);
-    free(scheduler->arrowList);
+    free(scheduler->arrowArray->array);
+    free(scheduler->arrowArray);
 }
 
 // -------------------------------------------------------------------------- //
diff --git a/src/arrows.c b/src/arrows.c
index 290079a..0e6419e 100644
--- a/src/arrows.c
+++ b/src/arrows.c
@@ -22,3 +22,5 @@
 #include "../include/base.h"
 
 /* -------------------------------------------------------------------------- */
+
+
diff --git a/src/cmds.c b/src/cmds.c
index 9faa487..da1d1b6 100644
--- a/src/cmds.c
+++ b/src/cmds.c
@@ -48,27 +48,15 @@ void *launchScheduler(void *args)
     // Creating structure for the model
     model0 = (Model_t*) calloc(1, sizeof(Model_t));
 
+    model0->space_xmax = XMAX;
+    model0->siteNumber = SITE_NUMBER;
+
     // Preparing global drawing space
     ModelPrepareSpace(scheduler0->globalDrawingSpace, model0);
 
-    scheduler0->arrowList = (ArrowArray_t*) calloc(1, sizeof(ArrowArray_t));
+    scheduler0->arrowArray = (ArrowArray_t*) calloc(1, sizeof(ArrowArray_t));
 
-    printLog("Populating a random arrow list...\n");
-
-    for (int i = 0; i < ARROW_NUMBER; i++) {
-
-        if (scheduler0->globalDrawingSpace->xmax)
-            scheduler0->arrowList->array[i].x =
-                rand() % (scheduler0->globalDrawingSpace->xmax + 1);
-
-        if (scheduler0->globalDrawingSpace->ymax)
-            scheduler0->arrowList->array[i].y =
-                rand() % (scheduler0->globalDrawingSpace->ymax + 1);
-
-        if (scheduler0->globalDrawingSpace->zmax)
-            scheduler0->arrowList->array[i].z =
-                rand() % (scheduler0->globalDrawingSpace->zmax + 1);
-    }
+    ModelPrepareArrows(scheduler0->globalDrawingSpace, scheduler0->arrowArray, model0);
 
     scheduler0->nmaxThread = MAX_THREAD;
     scheduler0->nmaxCycles = MAX_CYCLES;
diff --git a/src/model.c b/src/model.c
index ba01a2f..80153a4 100644
--- a/src/model.c
+++ b/src/model.c
@@ -20,6 +20,9 @@
 //=-------------------------------------------------------------------------=//
 
 #include "../include/base.h"
+#include "../include/arrows.h"
+
+static Model_t *loadedModels;
 
 void ModelPrepareSpace(Space_t *globalDrawingSpace, Model_t *model)
 {
@@ -37,20 +40,18 @@ void ModelPrepareSpace(Space_t *globalDrawingSpace, Model_t *model)
     }
 }
 
-void ModelPrepareArrows(Space_t *globalDrawingSpace, ArrowArray_t *arrowList,
+void ModelPrepareArrows(Space_t *globalDrawingSpace, ArrowArray_t *arrowArray,
                         Model_t *model)
 {
-#define ARROW_NUMBER 6
-
-    arrowList->array = (Arrow_t*) calloc(ARROW_NUMBER, sizeof(Arrow_t));
-    arrowList->size = ARROW_NUMBER;
+    arrowArray->array = (Arrow_t*) calloc(6, sizeof(Arrow_t));
+    arrowArray->size = 6;
 
     // Creating some arrows
     globalDrawingSpace->space[3].sites[1].narrow = 1;
-    arrowList->array[0].siteId = 1;
-    arrowList->array[0].x = 3;
+    arrowArray->array[0].siteId = 1;
+    arrowArray->array[0].x = 3;
 
     globalDrawingSpace->space[4].sites[0].narrow = 1;
-    arrowList->array[1].siteId = 0;
-    arrowList->array[1].x = 4;
+    arrowArray->array[1].siteId = 0;
+    arrowArray->array[1].x = 4;
 }
diff --git a/src/scheduler.c b/src/scheduler.c
index 68d17a4..aea2f34 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -22,6 +22,7 @@
 #include "../include/base.h"
 #include "../include/centers.h"
 #include "../include/localworker.h"
+#include "../include/arrows.h"
 
 #include <sys/sysinfo.h>
 
@@ -85,7 +86,7 @@ static void *schedulerMain(void *scheduler)
     // A cycle is defined as the total renew of all allocated workers.
     // 1 cycle = thread * partial cycle.
     int nPartialCycles;
-    int ncpu, nworker;
+    int ncpu, nworker, err;
 
     // Getting scheduler argument structure
     args = (Scheduler_t*) scheduler;
@@ -104,6 +105,11 @@ static void *schedulerMain(void *scheduler)
     centersList = (Center_t*) calloc(1, sizeof(Center_t));
     nPartialCycles = 0;
 
+    // Initiate the arrowArray lock
+    if (err = createArrowLock(args->arrowArray), err != 0) { // TODO destroy this
+        printLog("Impossible to create the arrow array lock (error %d)\n", err);
+        return NULL;
+    }
     //
     // MAIN LOOP
     //
@@ -114,17 +120,24 @@ static void *schedulerMain(void *scheduler)
 
         // Create a new thread
         if (nworker < ncpu) {
-            // Random choice of an arrow
-            electedArrow =
-                &args->arrowList->array[rand() % args->arrowList->size];
 
-            // Find a local area
-            workArea = findWorkArea(centersList, electedArrow, args->ruleRadius,
-                                    args->globalDrawingSpace->size,
-                                    args->globalDrawingSpace->xmax,
-                                    args->globalDrawingSpace->ymax,
-                                    args->globalDrawingSpace->zmax
-                                    );
+            workArea = NULL;
+
+            // Acquiring lock to consistently read the arrowArray
+            if (acquireNonBlockinArrowgLock(args->arrowArray)) { //XXX does not return 0
+                // Random choice of an arrow
+                electedArrow =
+                    &args->arrowArray->array[rand() % args->arrowArray->size]; // XXX size is 0
+
+                // Find a local area
+                workArea = findWorkArea(centersList, electedArrow, args->ruleRadius,
+                                        args->globalDrawingSpace->size,
+                                        args->globalDrawingSpace->xmax,
+                                        args->globalDrawingSpace->ymax,
+                                        args->globalDrawingSpace->zmax
+                                        );
+                releaseArrowLock(args->arrowArray);
+            }
 
             // If a free area exists,
             if (workArea) {
@@ -141,8 +154,8 @@ static void *schedulerMain(void *scheduler)
                             args->globalDrawingSpace;
                         workerArray[i].transitionsTree =
                             args->transitionsTree;
-                        workerArray[i].arrowList =
-                            args->arrowList;
+                        workerArray[i].arrowArray =
+                            args->arrowArray;
                         // create the worker,
                         WorkerInit(&workerArray[i]);
                         // and increment worker count.