X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/0a7eb8c381f11279a5b6e1e97a726ff8d0746bcd..98f86232eb9857c8c31067d5db378a6ad417165c:/src/simdag/sd_task.c

diff --git a/src/simdag/sd_task.c b/src/simdag/sd_task.c
index ea0d862093..5d13f2af3a 100644
--- a/src/simdag/sd_task.c
+++ b/src/simdag/sd_task.c
@@ -1,141 +1,598 @@
 #include "private.h"
 #include "simdag/simdag.h"
 #include "xbt/sysdep.h"
+#include "xbt/dynar.h"
 
-/* Creates a task.
+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 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) {
-  CHECK_INIT_DONE();
-  xbt_assert0(name != NULL, "name is NULL !");
-  xbt_assert0(amount >= 0, "amount must be positive"); /* or amount > 0 ? */
-
-  SD_task_data_t sd_data = xbt_new0(s_SD_task_data_t, 1); /* task private data */
-  sd_data->name = xbt_strdup(name);
-  sd_data->state = SD_SCHEDULED; /* not sure */
+  SD_CHECK_INIT_DONE();
 
   SD_task_t task = xbt_new0(s_SD_task_t, 1);
-  task->sd_data = sd_data; /* private data */
+
+  /* general information */
   task->data = data; /* user data */
+  if (name != NULL)
+    task->name = xbt_strdup(name);
+  else
+    task->name = NULL;
 
-  /* TODO: dependencies + watch */
+  task->state_set = sd_global->not_scheduled_task_set;
+  xbt_swag_insert(task,task->state_set);
 
-  return task;
-}
+  task->amount = amount;
+  task->surf_action = NULL;
+  task->watch_points = 0;
+  task->state_changed = 0;
 
-/* Schedules a task.
- */
-int SD_task_schedule(SD_task_t task, int workstation_nb,
-		     SD_workstation_t **workstation_list, double *computation_amount,
-		     double *communication_amount, double rate) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-  /* TODO */
+  /* dependencies */
+  task->tasks_before = xbt_dynar_new(sizeof(SD_dependency_t), NULL);
+  task->tasks_after = xbt_dynar_new(sizeof(SD_dependency_t), NULL);
+
+  /* scheduling parameters */
+  task->workstation_nb = 0;
+  task->workstation_list = NULL;
+  task->computation_amount = NULL;
+  task->communication_amount = NULL;
+  task->rate = 0;
 
-  return 0;
+  return task;
 }
 
-/* Returns the data of a task.
+/**
+ * \brief Returns the user data of a task
+ *
+ * \param task a task
+ * \return the user data associated with this task (can be \c NULL)
+ * \see SD_task_set_data()
  */
 void* SD_task_get_data(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
   return task->data;
 }
 
-/* Sets the data of a task.
+/**
+ * \brief Sets the user data of a task
+ *
+ * The new data can be \c NULL. The old data should have been freed first
+ * if it was not \c NULL.
+ *
+ * \param task a task
+ * \param data the new data you want to associate with this task
+ * \see SD_task_get_data()
  */
 void SD_task_set_data(SD_task_t task, void *data) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
   task->data = data;
 }
 
-/* Returns the name of a task.
+/**
+ * \brief Returns the state of a task
+ *
+ * \param task a task
+ * \return the current \ref e_SD_task_state_t "state" of this task:
+ * #SD_NOT_SCHEDULED, #SD_SCHEDULED, #SD_READY, #SD_RUNNING, #SD_DONE or #SD_FAILED
+ * \see e_SD_task_state_t
+ */
+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;
+}
+
+/* Changes the state of a task. Updates the swags and the flag sd_global->watch_point_reached.
+ */
+void __SD_task_set_state(SD_task_t task, e_SD_task_state_t new_state) {
+  xbt_swag_remove(task, task->state_set);
+  switch (new_state) {
+  case SD_NOT_SCHEDULED:
+    task->state_set = sd_global->not_scheduled_task_set;
+    break;
+  case SD_SCHEDULED:
+    task->state_set = sd_global->scheduled_task_set;
+    break;
+  case SD_READY:
+    task->state_set = sd_global->ready_task_set;
+    break;
+  case SD_RUNNING:
+    task->state_set = sd_global->running_task_set;
+    break;
+  case SD_DONE:
+    task->state_set = sd_global->done_task_set;
+    break;
+  case SD_FAILED:
+    task->state_set = sd_global->failed_task_set;
+    break;
+  default:
+    xbt_assert0(0, "Invalid state");
+  }
+  xbt_swag_insert(task, task->state_set);
+
+  if (task->watch_points & 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 */
+  }
+}
+
+/**
+ * \brief Returns the name of a task
+ *
+ * \param task a task
+ * \return the name of this task (can be \c NULL)
  */
 const char* SD_task_get_name(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-  return task->sd_data->name;
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+  return task->name;
 }
 
-/* Returns the computing amount of a task.
+/**
+ * \brief Returns the total amount of a task
+ *
+ * \param task a task
+ * \return the total amount of this task
+ * \see SD_task_get_remaining_amount()
  */
 double SD_task_get_amount(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-
-  /* TODO */
-  return 0;
-  /*return task->amount;*/
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+  return task->amount;
 }
 
-/* Returns the remaining computing amount of a task.
+/**
+ * \brief Returns the remaining amount of a task
+ *
+ * \param task a task
+ * \return the remaining amount of this task
+ * \see SD_task_get_amount()
  */
 double SD_task_get_remaining_amount(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter")
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+
+  if (task->surf_action)
+    return task->surf_action->remains;
+  else
+    return task->amount;
+}
+
+/* temporary function for debbuging */
+static void __SD_print_dependencies(SD_task_t 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);
+    INFO1(" %s", SD_task_get_name(dependency->src));
+  }
+
+  INFO1("The following tasks must be executed after %s:", SD_task_get_name(task));
 
-  /* TODO (surf encapsulation) */;
-  return 0;
+  dynar = task->tasks_after;
+  length = xbt_dynar_length(dynar);
+  for (i = 0; i < length; i++) {
+    xbt_dynar_get_cpy(dynar, i, &dependency);
+    INFO1(" %s", SD_task_get_name(dependency->dst));
+  }
+  INFO0("----------------------------");
 }
 
-/* Adds a dependency between two tasks.
+/* Destroys a dependency between two tasks.
+ */
+static void __SD_task_dependency_destroy(void *dependency) {
+  if (((SD_dependency_t) dependency)->name != NULL)
+    xbt_free(((SD_dependency_t) dependency)->name);
+  xbt_free(dependency);
+}
+
+/**
+ * \brief Adds a dependency between two tasks
+ *
+ * \a dst will depend on \a src, ie \a dst will not start before \a src is finished.
+ * Their \ref e_SD_task_state_t "state" must be #SD_NOT_SCHEDULED, #SD_SCHEDULED or #SD_READY.
+ *
+ * \param name the name of the new dependency (can be \c NULL)
+ * \param data the user data you want to associate with this dependency (can be \c NULL)
+ * \param src the task which must be executed first
+ * \param dst the task you want to make depend on \a src
+ * \see SD_task_dependency_remove()
  */
 void SD_task_dependency_add(const char *name, void *data, SD_task_t src, SD_task_t dst) {
-  CHECK_INIT_DONE();
+  SD_CHECK_INIT_DONE();
   xbt_assert0(src != NULL && dst != NULL, "Invalid parameter");
-  /* TODO */
+  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;
+  for (i = 0; i < length && !found; i++) {
+    xbt_dynar_get_cpy(dynar, i, &dependency);
+    found = (dependency->dst == 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 (name != NULL)
+    dependency->name = xbt_strdup(name);
+  else
+    dependency->name = NULL;
+
+  dependency->data = data;
+  dependency->src = src;
+  dependency->dst = dst;
+
+  /* src must be executed before dst */
+  xbt_dynar_push(src->tasks_after, &dependency);
+  xbt_dynar_push(dst->tasks_before, &dependency);
+
+  /* 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)) {
+    DEBUG1("SD_task_dependency_add: %s was ready and becomes scheduled!", SD_task_get_name(dst));
+    __SD_task_set_state(dst, SD_SCHEDULED);
+  }
+
+  /*  __SD_print_dependencies(src);
+      __SD_print_dependencies(dst); */
 }
 
-/* Removes a dependency between two tasks.
+/**
+ * \brief Remove a dependency between two tasks
+ *
+ * \param src a task
+ * \param dst a task depending on \a src
+ * \see SD_task_dependency_add()
  */
 void SD_task_dependency_remove(SD_task_t src, SD_task_t dst) {
-  CHECK_INIT_DONE();
+  SD_CHECK_INIT_DONE();
   xbt_assert0(src != NULL && dst != NULL, "Invalid parameter");
-  /* TODO */
+
+  /* remove the dependency from src->tasks_after */
+  xbt_dynar_t dynar = src->tasks_after;
+  int length = xbt_dynar_length(dynar);
+  int found = 0;
+  int i;
+  SD_dependency_t dependency;
+  for (i = 0; i < length && !found; i++) {
+    xbt_dynar_get_cpy(dynar, i, &dependency);
+    if (dependency->dst == dst) {
+      xbt_dynar_remove_at(dynar, i, NULL);
+      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));
+
+  /* remove the dependency from dst->tasks_before */
+  dynar = dst->tasks_before;
+  length = xbt_dynar_length(dynar);
+  found = 0;
+  
+  for (i = 0; i < length && !found; i++) {
+    xbt_dynar_get_cpy(dynar, i, &dependency);
+    if (dependency->src == src) {
+      xbt_dynar_remove_at(dynar, i, NULL);
+      __SD_task_dependency_destroy(dependency);
+      found = 1;
+    }
+  }
+  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... */
+
+  /* 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))
+    __SD_task_set_state(dst, SD_READY);
+
+  /*  __SD_print_dependencies(src); 
+      __SD_print_dependencies(dst);*/
 }
 
-/* Returns the state of a task: SD_SCHEDULED, SD_RUNNING, SD_DONE or SD_FAILED.
+/**
+ * \brief Returns the user data associated with a dependency between two tasks
+ *
+ * \param src a task
+ * \param dst a task depending on \a src
+ * \return the user data associated with this dependency (can be \c NULL)
+ * \see SD_task_dependency_add()
  */
-SD_task_state_t SD_task_get_state(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-  return task->sd_data->state;
+void *SD_task_dependency_get_data(SD_task_t src, SD_task_t dst) {
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(src != NULL && dst != NULL, "Invalid parameter");
+
+  xbt_dynar_t dynar = src->tasks_after;
+  int length = xbt_dynar_length(dynar);
+  int found = 0;
+  int i;
+  SD_dependency_t dependency;
+  for (i = 0; i < length && !found; i++) {
+    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));
+  return dependency->data;
+}
+
+/* temporary function for debugging */
+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"};
+
+  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])
+      INFO1("%s ", state_names[i]);
+  }
 }
 
-/* Adds a watch point to a task.
-   SD_simulate will stop as soon as the state of this task is the one given in argument.
-   Watch point is then automatically removed.
+/**
+ * \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
+ * 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)
+ * \see SD_task_unwatch()
  */
-void  SD_task_watch(SD_task_t task, SD_task_state_t state) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-  /* TODO */
+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");
+
+  task->watch_points = task->watch_points | state;
+  /*  __SD_print_watch_points(task);*/
+}
+
+/**
+ * \brief Removes a watch point from a task
+ * 
+ * \param task a task
+ * \param state the \ref e_SD_task_state_t "state" you no longer want to watch
+ * \see SD_task_watch()
+ */
+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");
+  
+  task->watch_points = task->watch_points & ~state;
+  /*  __SD_print_watch_points(task);*/
 }
 
-/* Removes a watch point from a task.
+/**
+ * \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()
  */
-void SD_task_unwatch(SD_task_t task, SD_task_state_t state) {
-  CHECK_INIT_DONE();
+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) {
+  /* 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);
+}
+
+/**
+ * \brief Schedules a task
+ *
+ * The task state must be #SD_NOT_SCHEDULED.
+ * Once scheduled, a task will be executed as soon as possible in SD_simulate(),
+ * i.e. when its dependencies are satisfied.
+ * 
+ * \param task the task you want to schedule
+ * \param workstation_nb number of workstations on which the task will be executed
+ * \param workstation_list the workstations on which the task will 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_task_unschedule()
+ */
+void SD_task_schedule(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_assert0(task, "Invalid parameter");
-  /* TODO */
+  xbt_assert1(__SD_task_is_not_scheduled(task), "Task '%s' has already been scheduled.", SD_task_get_name(task));
+  xbt_assert0(workstation_nb > 0, "workstation_nb must be positive");
+
+  task->workstation_nb = workstation_nb;
+  task->rate = rate;
+
+  task->computation_amount = xbt_new0(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);
+  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;
+  }
+
+  /* update the task state */
+  if (xbt_dynar_length(task->tasks_before) == 0)
+    __SD_task_set_state(task, SD_READY);
+  else
+    __SD_task_set_state(task, SD_SCHEDULED);
 }
 
-/* Unschedules a task.
-   Change state and rerun
+/**
+ * \brief Unschedules a task
+ *
+ * The task state must be #SD_SCHEDULED, #SD_READY, #SD_RUNNING or #SD_FAILED.
+ * If you call this function, the task state becomes #SD_NOT_SCHEDULED.
+ * Call SD_task_schedule() to schedule it again.
+ *
+ * \param task the task you want to unschedule
+ * \see SD_task_schedule()
  */
 void SD_task_unschedule(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_assert0(task, "Invalid parameter");
-  /* TODO */
+  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 (__SD_task_is_scheduled_or_ready(task)) /* if the task is scheduled or ready */
+    __SD_task_destroy_scheduling_data(task);
+
+  if (__SD_task_is_running(task)) /* the task should become SD_FAILED */
+    surf_workstation_resource->common_public->action_cancel(task->surf_action);
+  else
+    __SD_task_set_state(task, SD_NOT_SCHEDULED);
+}
+
+/* Destroys the data memorised by SD_task_schedule. Task state must be SD_SCHEDULED or SD_READY.
+ */
+static void __SD_task_destroy_scheduling_data(SD_task_t task) {
+  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);
 }
 
-/* Destroys a task. The user data (if any) should have been destroyed first.
+/* Runs a task. This function is called by SD_simulate() when a scheduled task can start
+ * (ie when its dependencies are satisfied).
+ */
+surf_action_t __SD_task_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));
+
+  surf_action_t surf_action = surf_workstation_resource->extension_public->
+    execute_parallel_task(task->workstation_nb,
+			  task->workstation_list,
+			  task->computation_amount,
+			  task->communication_amount,
+			  task->amount,
+			  task->rate);
+
+  DEBUG1("surf_action = %p", surf_action);
+
+  __SD_task_destroy_scheduling_data(task); /* now the scheduling data are not useful anymore */
+  __SD_task_set_state(task, SD_RUNNING);
+
+  return surf_action;
+}
+/* Remove all dependencies associated with a task. This function is called when the task is destroyed.
+ */
+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;
+  while (xbt_dynar_length(task->tasks_before) > 0) {
+    xbt_dynar_get_cpy(task->tasks_before, 0, &dependency);
+    SD_task_dependency_remove(dependency->src, dependency->dst);
+  }
+
+  while (xbt_dynar_length(task->tasks_after) > 0) {
+    xbt_dynar_get_cpy(task->tasks_after, 0, &dependency);
+    SD_task_dependency_remove(dependency->src, dependency->dst);
+  }
+}
+
+/**
+ * \brief Destroys a task.
+ *
+ * The user data (if any) should have been destroyed first.
+ *
+ * \param task the task you want to destroy
+ * \see SD_task_create()
  */
 void SD_task_destroy(SD_task_t task) {
-  CHECK_INIT_DONE();
-  xbt_free(task->sd_data->name);
+  SD_CHECK_INIT_DONE();
+  xbt_assert0(task != NULL, "Invalid parameter");
+
+  DEBUG1("Destroying task %s...", SD_task_get_name(task));
 
-  /* TODO: dependencies + watch */
+  __SD_task_remove_dependencies(task);
+
+  /* if the task was scheduled or ready we have to free the scheduling parameters */
+  if (__SD_task_is_scheduled_or_ready(task))
+    __SD_task_destroy_scheduling_data(task);
+
+  if (task->name != NULL)
+    xbt_free(task->name);
+
+  if (task->surf_action != NULL)
+    surf_workstation_resource->common_public->action_free(task->surf_action);
+
+  xbt_dynar_free(&task->tasks_before);
+  xbt_dynar_free(&task->tasks_after);
   xbt_free(task);
+
+  DEBUG0("Task destroyed.");
 }