X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/3f17e7a2d9e727cf8ba2da354280f3afd329c8a6..178d9ca3560ec4b1e756970b888b4e36212ce670:/src/simdag/sd_task.c

diff --git a/src/simdag/sd_task.c b/src/simdag/sd_task.c
index 4a046fa6b9..a19bd49c79 100644
--- a/src/simdag/sd_task.c
+++ b/src/simdag/sd_task.c
@@ -3,20 +3,25 @@
 #include "xbt/sysdep.h"
 #include "xbt/dynar.h"
 
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(sd_task,sd,
+				"Logging specific to SimDag (task)");
+
+static void __SD_task_remove_dependencies(SD_task_t task);
+static void __SD_task_destroy_scheduling_data(SD_task_t task);
+
 /**
  * \brief Creates a new task.
  *
  * \param name the name of the task (can be \c NULL)
  * \param data the user data you want to associate with the task (can be \c NULL)
- * \param amount the computing amount necessary to do this task
+ * \param amount amount of the task
  * \return the new task
  * \see SD_task_destroy()
  */
 SD_task_t SD_task_create(const char *name, void *data, double amount) {
   SD_CHECK_INIT_DONE();
-  xbt_assert0(amount > 0, "amount must be positive");
 
-  SD_task_t task = xbt_new0(s_SD_task_t, 1);
+  SD_task_t task = xbt_new(s_SD_task_t, 1);
 
   /* general information */
   task->data = data; /* user data */
@@ -26,9 +31,13 @@ SD_task_t SD_task_create(const char *name, void *data, double amount) {
     task->name = NULL;
 
   task->state_set = sd_global->not_scheduled_task_set;
+  task->state = SD_NOT_SCHEDULED;
   xbt_swag_insert(task,task->state_set);
 
   task->amount = amount;
+  task->remains = amount;
+  task->start_time = -1.0;
+  task->finish_time = -1.0;
   task->surf_action = NULL;
   task->watch_points = 0;
   task->state_changed = 0;
@@ -44,6 +53,8 @@ SD_task_t SD_task_create(const char *name, void *data, double amount) {
   task->communication_amount = NULL;
   task->rate = 0;
 
+  sd_global->task_number++;
+
   return task;
 }
 
@@ -87,18 +98,7 @@ void SD_task_set_data(SD_task_t task, void *data) {
 e_SD_task_state_t SD_task_get_state(SD_task_t task) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
-
-  if (task->state_set == sd_global->scheduled_task_set)
-    return SD_SCHEDULED;
-  if (task->state_set == sd_global->done_task_set)
-    return SD_DONE;
-  if (task->state_set == sd_global->running_task_set)
-    return SD_RUNNING;
-  if (task->state_set == sd_global->ready_task_set)
-    return SD_READY;
-  if (task->state_set == sd_global->not_scheduled_task_set)
-    return SD_NOT_SCHEDULED;
-  return SD_FAILED;
+  return task->state;
 }
 
 /* Changes the state of a task. Updates the swags and the flag sd_global->watch_point_reached.
@@ -115,11 +115,19 @@ void __SD_task_set_state(SD_task_t task, e_SD_task_state_t new_state) {
   case SD_READY:
     task->state_set = sd_global->ready_task_set;
     break;
+  case SD_IN_FIFO:
+    task->state_set = sd_global->in_fifo_task_set;
+    break;
   case SD_RUNNING:
     task->state_set = sd_global->running_task_set;
+    task->start_time = surf_workstation_resource->common_public->
+      action_get_start_time(task->surf_action);
     break;
   case SD_DONE:
     task->state_set = sd_global->done_task_set;
+    task->finish_time = surf_workstation_resource->common_public->
+      action_get_finish_time(task->surf_action);
+    task->remains = 0;
     break;
   case SD_FAILED:
     task->state_set = sd_global->failed_task_set;
@@ -128,9 +136,10 @@ void __SD_task_set_state(SD_task_t task, e_SD_task_state_t new_state) {
     xbt_assert0(0, "Invalid state");
   }
   xbt_swag_insert(task, task->state_set);
+  task->state = new_state;
 
   if (task->watch_points & new_state) {
-    printf("Watch point reached with task '%s' in state %d!\n", SD_task_get_name(task), new_state);
+    INFO1("Watch point reached with task '%s'!", SD_task_get_name(task));
     sd_global->watch_point_reached = 1;
     SD_task_unwatch(task, new_state); /* remove the watch point */
   }
@@ -149,10 +158,10 @@ const char* SD_task_get_name(SD_task_t task) {
 }
 
 /**
- * \brief Returns the computing amount of a task
+ * \brief Returns the total amount of a task
  *
  * \param task a task
- * \return the total computing amount of this task
+ * \return the total amount of this task
  * \see SD_task_get_remaining_amount()
  */
 double SD_task_get_amount(SD_task_t task) {
@@ -162,43 +171,43 @@ double SD_task_get_amount(SD_task_t task) {
 }
 
 /**
- * \brief Returns the remaining computing amount of a task
+ * \brief Returns the remaining amount of a task
  *
  * \param task a task
- * \return the remaining computing amount of this task
+ * \return the remaining amount of this task
  * \see SD_task_get_amount()
  */
 double SD_task_get_remaining_amount(SD_task_t task) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
-  
+
   if (task->surf_action)
-    return task->amount;
-  else
     return task->surf_action->remains;
+  else
+    return task->remains;
 }
 
 /* temporary function for debbuging */
 static void __SD_print_dependencies(SD_task_t task) {
-  printf("The following tasks must be executed before %s:", SD_task_get_name(task));
+  INFO1("The following tasks must be executed before %s:", SD_task_get_name(task));
   xbt_dynar_t dynar = task->tasks_before;
   int length = xbt_dynar_length(dynar);
   int i;
   SD_dependency_t dependency;
   for (i = 0; i < length; i++) {
     xbt_dynar_get_cpy(dynar, i, &dependency);
-    printf(" %s", SD_task_get_name(dependency->src));
+    INFO1(" %s", SD_task_get_name(dependency->src));
   }
 
-  printf("\nThe following tasks must be executed after %s:", SD_task_get_name(task));
+  INFO1("The following tasks must be executed after %s:", SD_task_get_name(task));
 
   dynar = task->tasks_after;
   length = xbt_dynar_length(dynar);
   for (i = 0; i < length; i++) {
     xbt_dynar_get_cpy(dynar, i, &dependency);
-    printf(" %s", SD_task_get_name(dependency->dst));
+    INFO1(" %s", SD_task_get_name(dependency->dst));
   }
-  printf("\n----------------------------\n");
+  INFO0("----------------------------");
 }
 
 /* Destroys a dependency between two tasks.
@@ -224,28 +233,41 @@ static void __SD_task_dependency_destroy(void *dependency) {
 void SD_task_dependency_add(const char *name, void *data, SD_task_t src, SD_task_t dst) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(src != NULL && dst != NULL, "Invalid parameter");
-  xbt_assert1(src != dst, "Cannot add a dependency between task '%s' and itself", SD_task_get_name(src));
-  xbt_assert1(__SD_task_is_not_scheduled(src) || __SD_task_is_scheduled_or_ready(src),
-	      "Task '%s' must be SD_NOT_SCHEDULED, SD_SCHEDULED or SD_READY", SD_task_get_name(src));
-  xbt_assert1(__SD_task_is_not_scheduled(dst) || __SD_task_is_scheduled_or_ready(dst),
-	      "Task '%s' must be SD_NOT_SCHEDULED, SD_SCHEDULED or SD_READY", SD_task_get_name(dst));
 
   xbt_dynar_t dynar = src->tasks_after;
   int length = xbt_dynar_length(dynar);
   int found = 0;
   int i;
   SD_dependency_t dependency;
+
+  if (src == dst) 
+    THROW1(arg_error, 0, "Cannot add a dependency between task '%s' and itself",
+	   SD_task_get_name(src));
+
+  if (!__SD_task_is_not_scheduled(src) && !__SD_task_is_scheduled_or_ready(src))
+    THROW1(arg_error, 0, "Task '%s' must be SD_NOT_SCHEDULED, SD_SCHEDULED or SD_READY", SD_task_get_name(src));
+
+  if (!__SD_task_is_not_scheduled(dst) && !__SD_task_is_scheduled_or_ready(dst))
+    THROW1(arg_error, 0, "Task '%s' must be SD_NOT_SCHEDULED, SD_SCHEDULED or SD_READY", SD_task_get_name(dst));
+
+  DEBUG2("SD_task_dependency_add: src = %s, dst = %s", SD_task_get_name(src), SD_task_get_name(dst));
   for (i = 0; i < length && !found; i++) {
     xbt_dynar_get_cpy(dynar, i, &dependency);
     found = (dependency->dst == dst);
+    DEBUG2("Dependency %d: dependency->dst = %s", i, SD_task_get_name(dependency->dst));
   }
-  xbt_assert2(!found, "A dependency already exists between task '%s' and task '%s'",
-	      SD_task_get_name(src), SD_task_get_name(dst));
 
-  dependency = xbt_new0(s_SD_dependency_t, 1);
+  if (found)
+    THROW2(arg_error, 0, "A dependency already exists between task '%s' and task '%s'",
+	   SD_task_get_name(src), SD_task_get_name(dst));
+
+  dependency = xbt_new(s_SD_dependency_t, 1);
 
   if (name != NULL)
     dependency->name = xbt_strdup(name);
+  else
+    dependency->name = NULL;
+
   dependency->data = data;
   dependency->src = src;
   dependency->dst = dst;
@@ -257,7 +279,7 @@ void SD_task_dependency_add(const char *name, void *data, SD_task_t src, SD_task
   /* if the task was ready, then dst->tasks_before is not empty anymore,
      so we must go back to state SD_SCHEDULED */
   if (__SD_task_is_ready(dst)) {
-    printf("SD_task_dependency_add: %s was ready and becomes scheduled!\n", SD_task_get_name(dst));
+    DEBUG1("SD_task_dependency_add: %s was ready and becomes scheduled!", SD_task_get_name(dst));
     __SD_task_set_state(dst, SD_SCHEDULED);
   }
 
@@ -289,8 +311,10 @@ void SD_task_dependency_remove(SD_task_t src, SD_task_t dst) {
       found = 1;
     }
   }
-  xbt_assert4(found, "No dependency found between task '%s' and '%s': task '%s' is not a successor of task '%s'",
-	      SD_task_get_name(src), SD_task_get_name(dst), SD_task_get_name(dst), SD_task_get_name(src));
+  if (!found)
+    THROW4(arg_error, 0,
+	   "No dependency found between task '%s' and '%s': task '%s' is not a successor of task '%s'",
+	   SD_task_get_name(src), SD_task_get_name(dst), SD_task_get_name(dst), SD_task_get_name(src));
 
   /* remove the dependency from dst->tasks_before */
   dynar = dst->tasks_before;
@@ -305,8 +329,9 @@ void SD_task_dependency_remove(SD_task_t src, SD_task_t dst) {
       found = 1;
     }
   }
+  /* should never happen... */
   xbt_assert4(found, "SimDag error: task '%s' is a successor of '%s' but task '%s' is not a predecessor of task '%s'",
-	      SD_task_get_name(dst), SD_task_get_name(src), SD_task_get_name(src), SD_task_get_name(dst)); /* should never happen... */
+	      SD_task_get_name(dst), SD_task_get_name(src), SD_task_get_name(src), SD_task_get_name(dst));
 
   /* if the task was scheduled and dst->tasks_before is empty now, we can make it ready */
   if (xbt_dynar_length(dst->tasks_before) == 0 && __SD_task_is_scheduled(dst))
@@ -337,7 +362,8 @@ void *SD_task_dependency_get_data(SD_task_t src, SD_task_t dst) {
     xbt_dynar_get_cpy(dynar, i, &dependency);
     found = (dependency->dst == dst);
   }
-  xbt_assert2(found, "No dependency found between task '%s' and '%s'", SD_task_get_name(src), SD_task_get_name(dst));
+  if (!found)
+    THROW2(arg_error, 0, "No dependency found between task '%s' and '%s'", SD_task_get_name(src), SD_task_get_name(dst));
   return dependency->data;
 }
 
@@ -346,30 +372,33 @@ static void __SD_print_watch_points(SD_task_t task) {
   static const int state_masks[] = {SD_SCHEDULED, SD_RUNNING, SD_READY, SD_DONE, SD_FAILED};
   static const char* state_names[] = {"scheduled", "running", "ready", "done", "failed"};
 
-  printf("Task '%s' watch points (%x): ", SD_task_get_name(task), task->watch_points);
+  INFO2("Task '%s' watch points (%x): ", SD_task_get_name(task), task->watch_points);
 
   int i;
   for (i = 0; i < 5; i++) {
     if (task->watch_points & state_masks[i])
-      printf("%s ", state_names[i]);
+      INFO1("%s ", state_names[i]);
   }
-  printf("\n");
 }
 
 /**
  * \brief Adds a watch point to a task
  *
- * SD_simulate() will stop as soon as the \ref e_SD_task_state_t "state" of this task becomes the one given in argument. The
+ * SD_simulate() will stop as soon as the \ref e_SD_task_state_t "state" of this
+ * task becomes the one given in argument. The
  * watch point is then automatically removed.
  * 
  * \param task a task
- * \param state the \ref e_SD_task_state_t "state" you want to watch (cannot be #SD_NOT_SCHEDULED)
+ * \param state the \ref e_SD_task_state_t "state" you want to watch
+ * (cannot be #SD_NOT_SCHEDULED)
  * \see SD_task_unwatch()
  */
 void SD_task_watch(SD_task_t task, e_SD_task_state_t state) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
-  xbt_assert0(state != SD_NOT_SCHEDULED, "Cannot add a watch point for state SD_NOT_SCHEDULED");
+
+  if (state & SD_NOT_SCHEDULED)
+    THROW0(arg_error, 0, "Cannot add a watch point for state SD_NOT_SCHEDULED");
 
   task->watch_points = task->watch_points | state;
   /*  __SD_print_watch_points(task);*/
@@ -385,21 +414,54 @@ void SD_task_watch(SD_task_t task, e_SD_task_state_t state) {
 void SD_task_unwatch(SD_task_t task, e_SD_task_state_t state) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
-  xbt_assert0(state != SD_NOT_SCHEDULED, "Cannot have a watch point for state SD_NOT_SCHEDULED");
+  xbt_assert0(state != SD_NOT_SCHEDULED,
+	      "SimDag error: Cannot have a watch point for state SD_NOT_SCHEDULED");
   
   task->watch_points = task->watch_points & ~state;
   /*  __SD_print_watch_points(task);*/
 }
 
-/* Destroys the data memorised by SD_task_schedule. Task state must be SD_SCHEDULED or SD_READY.
+/**
+ * \brief Returns an approximative estimation of the execution time of a task.
+ * 
+ * The estimation is very approximative because the value returned is the time
+ * the task would take if it was executed now and if it was the only task.
+ * 
+ * \param task the task to evaluate
+ * \param workstation_nb number of workstations on which the task would be executed
+ * \param workstation_list the workstations on which the task would be executed
+ * \param computation_amount computation amount for each workstation
+ * \param communication_amount communication amount between each pair of workstations
+ * \param rate task execution speed rate
+ * \see SD_schedule()
  */
-static void __SD_task_destroy_scheduling_data(SD_task_t task) {
+double SD_task_get_execution_time(SD_task_t task,
+				  int workstation_nb,
+				  const SD_workstation_t *workstation_list,
+				  const double *computation_amount,
+				  const double *communication_amount,
+				  double rate) {
   SD_CHECK_INIT_DONE();
-  xbt_assert1(__SD_task_is_scheduled_or_ready(task),
-	      "Task '%s' must be SD_SCHEDULED or SD_READY", SD_task_get_name(task));
-  xbt_free(task->workstation_list);
-  xbt_free(task->computation_amount);
-  xbt_free(task->communication_amount);
+  xbt_assert0(task != NULL && workstation_nb > 0 && workstation_list != NULL &&
+	      computation_amount != NULL && communication_amount != NULL,
+	      "Invalid parameter");
+
+  /* the task execution time is the maximum execution time of the parallel tasks */
+  double time, max_time = 0.0;
+  int i, j;
+  for (i = 0; i < workstation_nb; i++) {
+    time = SD_workstation_get_computation_time(workstation_list[i], computation_amount[i]);
+    
+    for (j = 0; j < workstation_nb; j++) {
+      time += SD_route_get_communication_time(workstation_list[i], workstation_list[j],
+					      communication_amount[i * workstation_nb + j]);
+    }
+
+    if (time > max_time) {
+      max_time = time;
+    }
+  }
+  return max_time * SD_task_get_amount(task);
 }
 
 /**
@@ -418,29 +480,27 @@ static void __SD_task_destroy_scheduling_data(SD_task_t task) {
  * \see SD_task_unschedule()
  */
 void SD_task_schedule(SD_task_t task, int workstation_nb,
-		     const SD_workstation_t *workstation_list, double *computation_amount,
-		     double *communication_amount, double rate) {
+		     const SD_workstation_t *workstation_list, const double *computation_amount,
+		     const double *communication_amount, double rate) {
   SD_CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-  xbt_assert1(__SD_task_is_not_scheduled(task), "Task '%s' has already been scheduled.", SD_task_get_name(task));
+  xbt_assert0(task != NULL, "Invalid parameter");
   xbt_assert0(workstation_nb > 0, "workstation_nb must be positive");
 
+  if (!__SD_task_is_not_scheduled(task))
+    THROW1(arg_error, 0, "Task '%s' has already been scheduled", SD_task_get_name(task));
+
   task->workstation_nb = workstation_nb;
   task->rate = rate;
 
-  task->computation_amount = xbt_new0(double, workstation_nb);
+  task->computation_amount = xbt_new(double, workstation_nb);
   memcpy(task->computation_amount, computation_amount, sizeof(double) * workstation_nb);
 
   int communication_nb = workstation_nb * workstation_nb;
-  task->communication_amount = xbt_new0(double, communication_nb);
+  task->communication_amount = xbt_new(double, communication_nb);
   memcpy(task->communication_amount, communication_amount, sizeof(double) * communication_nb);
 
-  /* we have to create a Surf workstation array instead of the SimDag workstation array */
-  task->workstation_list = xbt_new0(void*, workstation_nb);
-  int i;
-  for (i = 0; i < workstation_nb; i++) {
-    task->workstation_list[i] = workstation_list[i]->surf_workstation;
-  }
+  task->workstation_list = xbt_new(SD_workstation_t, workstation_nb);
+  memcpy(task->workstation_list, workstation_list, sizeof(SD_workstation_t) * workstation_nb);
 
   /* update the task state */
   if (xbt_dynar_length(task->tasks_before) == 0)
@@ -462,12 +522,13 @@ void SD_task_schedule(SD_task_t task, int workstation_nb,
 void SD_task_unschedule(SD_task_t task) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
-  xbt_assert1(task->state_set == sd_global->scheduled_task_set ||
-	      task->state_set == sd_global->ready_task_set ||
-	      task->state_set == sd_global->running_task_set ||
-	      task->state_set == sd_global->failed_task_set,
-	      "Task %s: the state must be SD_SCHEDULED, SD_READY, SD_RUNNING or SD_FAILED",
-	      SD_task_get_name(task));
+
+  if (task->state_set != sd_global->scheduled_task_set &&
+      task->state_set != sd_global->ready_task_set &&
+      task->state_set != sd_global->running_task_set &&
+      task->state_set != sd_global->failed_task_set)
+    THROW1(arg_error, 0, "Task %s: the state must be SD_SCHEDULED, SD_READY, SD_RUNNING or SD_FAILED",
+	   SD_task_get_name(task));
 
   if (__SD_task_is_scheduled_or_ready(task)) /* if the task is scheduled or ready */
     __SD_task_destroy_scheduling_data(task);
@@ -476,34 +537,246 @@ void SD_task_unschedule(SD_task_t task) {
     surf_workstation_resource->common_public->action_cancel(task->surf_action);
   else
     __SD_task_set_state(task, SD_NOT_SCHEDULED);
+  task->remains = task->amount;
+  task->start_time = -1.0;
 }
 
-/* Runs a task. This function is called by SD_simulate when a scheduled task can start
- * (ie when its dependencies are satisfied).
+/* Destroys the data memorised by SD_task_schedule. Task state must be SD_SCHEDULED or SD_READY.
  */
-surf_action_t __SD_task_run(SD_task_t task) {
+static void __SD_task_destroy_scheduling_data(SD_task_t task) {
+  SD_CHECK_INIT_DONE();
+  if (!__SD_task_is_scheduled_or_ready(task) && !__SD_task_is_in_fifo(task))
+    THROW1(arg_error, 0, "Task '%s' must be SD_SCHEDULED, SD_READY or SD_IN_FIFO", SD_task_get_name(task));
+
+  xbt_free(task->computation_amount);
+  xbt_free(task->communication_amount);
+}
+
+/* Runs a task. This function is directly called by __SD_task_try_to_run if the task
+ * doesn't have to wait in fifos. Otherwise, it is called by __SD_task_just_done when
+ * the task gets out of its fifos.
+ */
+void __SD_task_really_run(SD_task_t task) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
-  xbt_assert2(__SD_task_is_ready(task), "Task '%s' is not ready! Task state: %d",
-	      SD_task_get_name(task), SD_task_get_state(task));
+  xbt_assert2(__SD_task_is_ready_or_in_fifo(task), "Task '%s' is not ready or in a fifo! Task state: %d",
+	   SD_task_get_name(task), SD_task_get_state(task));
+  xbt_assert1(task->workstation_list != NULL, "Task '%s': workstation_list is NULL!", SD_task_get_name(task));
 
-  surf_action_t surf_action = surf_workstation_resource->extension_public->
+  int i;
+  void **surf_workstations;
+
+  DEBUG1("Really running task '%s'", SD_task_get_name(task));
+
+  /* set this task as current task for the workstations in sequential mode */
+  for (i = 0; i < task->workstation_nb; i++) {
+    if (SD_workstation_get_access_mode(task->workstation_list[i]) == SD_WORKSTATION_SEQUENTIAL_ACCESS) {
+      task->workstation_list[i]->current_task = task;
+      xbt_assert0(__SD_workstation_is_busy(task->workstation_list[i]), "The workstation should be busy now");
+    }
+  }
+  
+  DEBUG1("Task '%s' set as current task for its workstations", SD_task_get_name(task));
+
+  /* start the task */
+
+  /* we have to create a Surf workstation array instead of the SimDag workstation array */
+  surf_workstations = xbt_new(void*, task->workstation_nb);
+
+  for (i = 0; i < task->workstation_nb; i++) {
+    surf_workstations[i] = task->workstation_list[i]->surf_workstation;
+  }
+  
+  task->surf_action = surf_workstation_resource->extension_public->
     execute_parallel_task(task->workstation_nb,
-			  task->workstation_list,
+			  surf_workstations,
 			  task->computation_amount,
 			  task->communication_amount,
 			  task->amount,
 			  task->rate);
+  surf_workstation_resource->common_public->action_set_data(task->surf_action, task);
+  task->state_changed = 1;
+
+  DEBUG1("surf_action = %p",  task->surf_action);
 
+  xbt_free(surf_workstations);
   __SD_task_destroy_scheduling_data(task); /* now the scheduling data are not useful anymore */
   __SD_task_set_state(task, SD_RUNNING);
+  xbt_assert2(__SD_task_is_running(task), "Bad state of task '%s': %d",
+	      SD_task_get_name(task), SD_task_get_state(task));
+
+}
+
+/* Tries to run a task. This function is called by SD_simulate() when a scheduled task becomes SD_READY
+ * (ie when its dependencies are satisfied).
+ * If one of the workstations where the task is scheduled on is busy (in sequential mode),
+ * the task doesn't start.
+ * Returns whether the task has started.
+ */
+int __SD_task_try_to_run(SD_task_t task) {
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+  xbt_assert2(__SD_task_is_ready(task), "Task '%s' is not ready! Task state: %d",
+	   SD_task_get_name(task), SD_task_get_state(task));
+
+  int can_start = 1;
+  int i;
+  SD_workstation_t workstation;
+
+  for (i = 0; i < task->workstation_nb; i++) {
+    can_start = !__SD_workstation_is_busy(task->workstation_list[i]);
+  }
+
+  DEBUG2("Task '%s' can start: %d", SD_task_get_name(task), can_start);
+  
+  if (!can_start) { /* if the task cannot start and is not in the fifos yet*/
+    for (i = 0; i < task->workstation_nb; i++) {
+      workstation = task->workstation_list[i];
+      if (workstation->access_mode == SD_WORKSTATION_SEQUENTIAL_ACCESS) {
+	DEBUG2("Pushing task '%s' in the fifo of workstation '%s'", SD_task_get_name(task),
+	       SD_workstation_get_name(workstation));
+	xbt_fifo_push(workstation->task_fifo, task);
+      }
+    }
+    __SD_task_set_state(task, SD_IN_FIFO);
+    xbt_assert2(__SD_task_is_in_fifo(task), "Bad state of task '%s': %d",
+		SD_task_get_name(task), SD_task_get_state(task));
+    DEBUG1("Task '%s' state is now SD_IN_FIFO", SD_task_get_name(task));
+  }
+  else {
+    __SD_task_really_run(task);
+  }
+
+  return can_start;
+}
+
+/* This function is called by SD_simulate when a task is done.
+ * It updates task->state and task->action and executes if necessary the tasks
+ * which were waiting in fifos for the end of `task'
+ */
+void __SD_task_just_done(SD_task_t task) {
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+  xbt_assert1(__SD_task_is_running(task), "The task must be running! Task state: %d", SD_task_get_state(task));
+  xbt_assert1(task->workstation_list != NULL, "Task '%s': workstation_list is NULL!", SD_task_get_name(task));
+
+  int i, j;
+  SD_workstation_t workstation;
+
+  SD_task_t candidate;
+  int candidate_nb = 0;
+  int candidate_capacity = 8;
+  SD_task_t *candidates = xbt_new(SD_task_t, 8);
+  int can_start = 1;
+
+  __SD_task_set_state(task, SD_DONE);
+  surf_workstation_resource->common_public->action_free(task->surf_action);
+  task->surf_action = NULL;
+
+  DEBUG0("Looking for candidates");
+
+  /* if the task was executed on sequential workstations,
+     maybe we can execute the next task of the fifo for each workstation */
+  for (i = 0; i < task->workstation_nb; i++) {
+    workstation = task->workstation_list[i];
+    DEBUG2("Workstation '%s': access_mode = %d", SD_workstation_get_name(workstation), workstation->access_mode);
+    if (workstation->access_mode == SD_WORKSTATION_SEQUENTIAL_ACCESS) {
+      xbt_assert1(workstation->task_fifo != NULL, "Workstation '%s' has sequential access but no fifo!",
+		  SD_workstation_get_name(workstation));
+      xbt_assert2(workstation->current_task = task, "Workstation '%s': current task should be '%s'",
+		  SD_workstation_get_name(workstation), SD_task_get_name(task));
+
+      /* the task is over so we can release the workstation */
+      workstation->current_task = NULL;
+
+      DEBUG0("Getting candidate in fifo");
+      candidate = xbt_fifo_get_item_content(xbt_fifo_get_first_item(workstation->task_fifo));
+
+      if (candidate != NULL) {
+	DEBUG1("Candidate: '%s'", SD_task_get_name(candidate));
+	xbt_assert2(__SD_task_is_in_fifo(candidate), "Bad state of candidate '%s': %d",
+		    SD_task_get_name(candidate), SD_task_get_state(candidate));
+      }
+
+      DEBUG1("Candidate in fifo: %p", candidate);
+
+      /* if there was a task waiting for my place */
+      if (candidate != NULL) {
+	/* Unfortunately, we are not sure yet that we can execute the task now,
+	   because the task can be waiting more deeply in some other workstation's fifos...
+	   So we memorize all candidate tasks, and then we will check for each candidate
+	   whether or not all its workstations are available. */
+
+	/* realloc if necessary */
+	if (candidate_nb == candidate_capacity) {
+	  candidate_capacity *= 2;
+	  candidates = xbt_realloc(candidates, sizeof(SD_task_t) * candidate_capacity);
+	}
+
+	/* register the candidate */
+	candidates[candidate_nb++] = candidate;
+	candidate->fifo_checked = 0;
+      }
+    }
+  }
+
+  DEBUG1("Candidates found: %d", candidate_nb);
+
+  /* now we check every candidate task */
+  for (i = 0; i < candidate_nb; i++) {
+    candidate = candidates[i];
+
+    if (candidate->fifo_checked) {
+      continue; /* we have already evaluated that task*/
+    }
+
+    xbt_assert2(__SD_task_is_in_fifo(candidate), "Bad state of candidate '%s': %d",
+		SD_task_get_name(candidate), SD_task_get_state(candidate));
+
+    for (j = 0; j < candidate->workstation_nb && can_start; j++) {
+      workstation = candidate->workstation_list[j];
 
-  return surf_action;
+      /* I can start on this workstation if the workstation is shared
+	 or if I am the first task in the fifo */
+      can_start = workstation->access_mode == SD_WORKSTATION_SHARED_ACCESS ||
+	candidate == xbt_fifo_get_item_content(xbt_fifo_get_first_item(workstation->task_fifo));
+    }
+
+    DEBUG2("Candidate '%s' can start: %d", SD_task_get_name(candidate), can_start);
+
+    /* now we are sure that I can start! */
+    if (can_start) {
+      for (j = 0; j < candidate->workstation_nb && can_start; j++) {
+	workstation = candidate->workstation_list[j];
+
+	/* update the fifo */
+	if (workstation->access_mode == SD_WORKSTATION_SEQUENTIAL_ACCESS) {
+	  candidate = xbt_fifo_shift(workstation->task_fifo); /* the return value is stored just for debugging */
+	  DEBUG1("Head of the fifo: '%s'", (candidate != NULL) ? SD_task_get_name(candidate) : "NULL");
+	  xbt_assert0(candidate == candidates[i], "Error in __SD_task_just_done: bad first task in the fifo");
+	}
+      } /* for each workstation */
+      
+      /* finally execute the task */
+      DEBUG2("Task '%s' state: %d", SD_task_get_name(candidate), SD_task_get_state(candidate));
+      __SD_task_really_run(candidate);
+      
+      DEBUG4("Calling __SD_task_is_running: task '%s', state set: %p, running_task_set: %p, is running: %d",
+	     SD_task_get_name(candidate), candidate->state_set, sd_global->running_task_set, __SD_task_is_running(candidate));
+      xbt_assert2(__SD_task_is_running(candidate), "Bad state of task '%s': %d",
+		  SD_task_get_name(candidate), SD_task_get_state(candidate));
+      DEBUG0("Okay, the task is running.");
+
+    } /* can start */
+    candidate->fifo_checked = 1;
+  } /* for each candidate */ 
+  
+  xbt_free(candidates);
 }
 
-/* Remove all dependencies associated with a task. This function is called when the task is done.
+/* Remove all dependencies associated with a task. This function is called when the task is destroyed.
  */
-void __SD_task_remove_dependencies(SD_task_t task) {
+static void __SD_task_remove_dependencies(SD_task_t task) {
   /* we must destroy the dependencies carefuly (with SD_dependency_remove)
      because each one is stored twice */
   SD_dependency_t dependency;
@@ -518,6 +791,44 @@ void __SD_task_remove_dependencies(SD_task_t task) {
   }
 }
 
+/**
+ * \brief Returns the start time of a task
+ *
+ * The task state must be SD_RUNNING, SD_DONE or SD_FAILED.
+ *
+ * \param task: a task
+ * \return the start time of this task
+ */
+double SD_task_get_start_time(SD_task_t task) {
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+  if(task->surf_action)
+    return surf_workstation_resource->common_public->action_get_start_time(task->surf_action);
+  else 
+    return task->start_time;
+}
+
+/**
+ * \brief Returns the finish time of a task
+ *
+ * The task state must be SD_RUNNING, SD_DONE or SD_FAILED.
+ * If the state is not completed yet, the returned value is an
+ * estimation of the task finish time. This value can fluctuate 
+ * until the task is completed.
+ *
+ * \param task: a task
+ * \return the start time of this task
+ */
+double SD_task_get_finish_time(SD_task_t task) {
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+
+  if(task->surf_action) /* should never happen as actions are destroyed right after their completion */
+    return surf_workstation_resource->common_public->action_get_finish_time(task->surf_action);
+  else 
+    return task->finish_time;
+}
+
 /**
  * \brief Destroys a task.
  *
@@ -530,7 +841,7 @@ void SD_task_destroy(SD_task_t task) {
   SD_CHECK_INIT_DONE();
   xbt_assert0(task != NULL, "Invalid parameter");
 
-  /*printf("Destroying task %s...\n", SD_task_get_name(task));*/
+  DEBUG1("Destroying task %s...", SD_task_get_name(task));
 
   __SD_task_remove_dependencies(task);
 
@@ -541,9 +852,17 @@ void SD_task_destroy(SD_task_t task) {
   if (task->name != NULL)
     xbt_free(task->name);
 
+  if (task->surf_action != NULL)
+    surf_workstation_resource->common_public->action_free(task->surf_action);
+
+  if (task->workstation_list != NULL)
+    xbt_free(task->workstation_list);
+
   xbt_dynar_free(&task->tasks_before);
   xbt_dynar_free(&task->tasks_after);
   xbt_free(task);
 
-  /*printf("Task destroyed.\n");*/
+  sd_global->task_number--;
+
+  DEBUG0("Task destroyed.");
 }