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prevent tasks to share resources when they don't have to.
[simgrid.git] / src / simdag / sd_task.c
index 555f6ef..9465be4 100644 (file)
@@ -1,4 +1,4 @@
-/* Copyright (c) 2006, 2007, 2008, 2009, 2010. The SimGrid Team.
+/* Copyright (c) 2006, 2007, 2008, 2009, 2010, 2011. The SimGrid Team.
  * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
@@ -16,44 +16,39 @@ XBT_LOG_NEW_DEFAULT_SUBCATEGORY(sd_task, sd,
 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)
+void* SD_task_new_f(void)
 {
+  SD_task_t task = xbt_new0(s_SD_task_t, 1);
+  task->tasks_before = xbt_dynar_new(sizeof(SD_dependency_t), NULL);
+  task->tasks_after = xbt_dynar_new(sizeof(SD_dependency_t), NULL);
 
-  SD_task_t task;
-  SD_CHECK_INIT_DONE();
+  return task;
+}
 
-  task = xbt_new(s_SD_task_t, 1);
+void SD_task_recycle_f(void *t)
+{
+  SD_task_t task = (SD_task_t) t;
 
-  /* general information */
-  task->data = data;            /* user data */
-  task->name = xbt_strdup(name);
+  /* Reset the content */
   task->kind = SD_TASK_NOT_TYPED;
   task->state_hookup.prev = NULL;
   task->state_hookup.next = NULL;
   task->state_set = sd_global->not_scheduled_task_set;
+  xbt_swag_insert(task, task->state_set);
   task->state = SD_NOT_SCHEDULED;
+  task->return_hookup.prev = NULL;
+  task->return_hookup.next = NULL;
+
   task->marked = 0;
-  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;
 
   /* dependencies */
-  task->tasks_before = xbt_dynar_new(sizeof(SD_dependency_t), NULL);
-  task->tasks_after = xbt_dynar_new(sizeof(SD_dependency_t), NULL);
+  xbt_dynar_reset(task->tasks_before);
+  xbt_dynar_reset(task->tasks_after);
   task->unsatisfied_dependencies = 0;
   task->is_not_ready = 0;
 
@@ -63,6 +58,35 @@ SD_task_t SD_task_create(const char *name, void *data, double amount)
   task->computation_amount = NULL;
   task->communication_amount = NULL;
   task->rate = -1;
+}
+
+void SD_task_free_f(void *t)
+{
+  SD_task_t task = (SD_task_t)t;
+
+  xbt_dynar_free(&task->tasks_before);
+  xbt_dynar_free(&task->tasks_after);
+  xbt_free(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)
+{
+  SD_task_t task = xbt_mallocator_get(sd_global->task_mallocator);
+
+  /* general information */
+  task->data = data;            /* user data */
+  task->name = xbt_strdup(name);
+  task->amount = amount;
+  task->remains = amount;
 
   sd_global->task_number++;
 
@@ -73,6 +97,46 @@ SD_task_t SD_task_create(const char *name, void *data, double amount)
   return task;
 }
 
+/**
+ * \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)
+{
+  XBT_DEBUG("Destroying task %s...", SD_task_get_name(task));
+
+  __SD_task_remove_dependencies(task);
+  /* if the task was scheduled or runnable we have to free the scheduling parameters */
+  if (__SD_task_is_scheduled_or_runnable(task))
+    __SD_task_destroy_scheduling_data(task);
+  if (task->state_set != NULL) /* would be null if just created */
+    xbt_swag_remove(task, task->state_set);
+
+  xbt_swag_remove(task, sd_global->return_set);
+
+  xbt_free(task->name);
+
+  if (task->surf_action != NULL)
+    surf_workstation_model->action_unref(task->surf_action);
+
+  xbt_free(task->workstation_list);
+  xbt_free(task->communication_amount);
+  xbt_free(task->computation_amount);
+
+  xbt_mallocator_release(sd_global->task_mallocator,task);
+  sd_global->task_number--;
+
+#ifdef HAVE_TRACING
+  TRACE_sd_task_destroy(task);
+#endif
+
+  XBT_DEBUG("Task destroyed.");
+}
+
 /**
  * \brief Returns the user data of a task
  *
@@ -82,8 +146,6 @@ SD_task_t SD_task_create(const char *name, void *data, double amount)
  */
 void *SD_task_get_data(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   return task->data;
 }
 
@@ -99,8 +161,6 @@ void *SD_task_get_data(SD_task_t task)
  */
 void SD_task_set_data(SD_task_t task, void *data)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   task->data = data;
 }
 
@@ -114,8 +174,6 @@ 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_assert(task != NULL, "Invalid parameter");
   return task->state;
 }
 
@@ -178,8 +236,6 @@ void __SD_task_set_state(SD_task_t task, e_SD_task_state_t new_state)
  */
 const char *SD_task_get_name(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   return task->name;
 }
 
@@ -201,8 +257,6 @@ xbt_dynar_t SD_task_get_parents(SD_task_t task)
   unsigned int i;
   xbt_dynar_t parents;
   SD_dependency_t dep;
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
 
   parents = xbt_dynar_new(sizeof(SD_task_t), NULL);
   xbt_dynar_foreach(task->tasks_before, i, dep) {
@@ -221,8 +275,6 @@ xbt_dynar_t SD_task_get_children(SD_task_t task)
   unsigned int i;
   xbt_dynar_t children;
   SD_dependency_t dep;
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
 
   children = xbt_dynar_new(sizeof(SD_task_t), NULL);
   xbt_dynar_foreach(task->tasks_after, i, dep) {
@@ -239,10 +291,6 @@ xbt_dynar_t SD_task_get_children(SD_task_t task)
  */
 int SD_task_get_workstation_count(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-  //xbt_assert(task->state_set != sd_global->scheduled_task_set,
-  //           "Unscheduled task %s", task->name);
   return task->workstation_nb;
 }
 
@@ -254,10 +302,6 @@ int SD_task_get_workstation_count(SD_task_t task)
  */
 SD_workstation_t *SD_task_get_workstation_list(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-  //xbt_assert(task->state_set != sd_global->scheduled_task_set,
-  //           "Unscheduled task %s", task->name);
   return task->workstation_list;
 }
 
@@ -270,8 +314,6 @@ SD_workstation_t *SD_task_get_workstation_list(SD_task_t task)
  */
 double SD_task_get_amount(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   return task->amount;
 }
 
@@ -284,9 +326,6 @@ double SD_task_get_amount(SD_task_t task)
  */
 double SD_task_get_remaining_amount(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-
   if (task->surf_action)
     return surf_workstation_model->get_remains(task->surf_action);
   else
@@ -333,14 +372,14 @@ void SD_task_dump(SD_task_t task)
     }
   }
   XBT_INFO("  - amount: %.0f", SD_task_get_amount(task));
-  XBT_INFO("  - Dependencies to satisfy: %d", task->unsatisfied_dependencies);
-  if (xbt_dynar_length(task->tasks_before)) {
+  XBT_INFO("  - Dependencies to satisfy: %u", task->unsatisfied_dependencies);
+  if (!xbt_dynar_is_empty(task->tasks_before)) {
     XBT_INFO("  - pre-dependencies:");
     xbt_dynar_foreach(task->tasks_before, counter, dependency) {
       XBT_INFO("    %s", SD_task_get_name(dependency->src));
     }
   }
-  if (xbt_dynar_length(task->tasks_after)) {
+  if (!xbt_dynar_is_empty(task->tasks_after)) {
     XBT_INFO("  - post-dependencies:");
     xbt_dynar_foreach(task->tasks_after, counter, dependency) {
       XBT_INFO("    %s", SD_task_get_name(dependency->dst));
@@ -374,8 +413,7 @@ void SD_task_dotty(SD_task_t task, void *out)
  */
 static void __SD_task_dependency_destroy(void *dependency)
 {
-  if (((SD_dependency_t) dependency)->name != NULL)
-    xbt_free(((SD_dependency_t) dependency)->name);
+  xbt_free(((SD_dependency_t)dependency)->name);
   xbt_free(dependency);
 }
 
@@ -400,9 +438,6 @@ void SD_task_dependency_add(const char *name, void *data, SD_task_t src,
   int i;
   SD_dependency_t dependency;
 
-  SD_CHECK_INIT_DONE();
-  xbt_assert(src != NULL && dst != NULL, "Invalid parameter");
-
   dynar = src->tasks_after;
   length = xbt_dynar_length(dynar);
 
@@ -412,9 +447,10 @@ void SD_task_dependency_add(const char *name, void *data, SD_task_t src,
            SD_task_get_name(src));
 
   if (!__SD_task_is_not_scheduled(src) && !__SD_task_is_schedulable(src)
-      && !__SD_task_is_scheduled_or_runnable(src))
+      && !__SD_task_is_scheduled_or_runnable(src) && !__SD_task_is_running(src))
     THROWF(arg_error, 0,
-           "Task '%s' must be SD_NOT_SCHEDULED, SD_SCHEDULABLE, SD_SCHEDULED or SD_RUNNABLE",
+           "Task '%s' must be SD_NOT_SCHEDULED, SD_SCHEDULABLE, SD_SCHEDULED or SD_RUNNABLE"
+          " or SD_RUNNING",
            SD_task_get_name(src));
 
   if (!__SD_task_is_not_scheduled(dst) && !__SD_task_is_schedulable(dst)
@@ -465,7 +501,7 @@ void SD_task_dependency_add(const char *name, void *data, SD_task_t src,
 }
 
 /**
- * \brief Indacates whether there is a dependency between two tasks.
+ * \brief Indicates whether there is a dependency between two tasks.
  *
  * \param src a task
  * \param dst a task depending on \a src
@@ -478,7 +514,6 @@ int SD_task_dependency_exists(SD_task_t src, SD_task_t dst)
   unsigned int counter;
   SD_dependency_t dependency;
 
-  SD_CHECK_INIT_DONE();
   xbt_assert(src != NULL
               || dst != NULL,
               "Invalid parameter: both src and dst are NULL");
@@ -514,9 +549,6 @@ void SD_task_dependency_remove(SD_task_t src, SD_task_t dst)
   int i;
   SD_dependency_t dependency;
 
-  SD_CHECK_INIT_DONE();
-  xbt_assert(src != NULL && dst != NULL, "Invalid parameter");
-
   /* remove the dependency from src->tasks_after */
   dynar = src->tasks_after;
   length = xbt_dynar_length(dynar);
@@ -588,10 +620,6 @@ void *SD_task_dependency_get_data(SD_task_t src, SD_task_t dst)
   int i;
   SD_dependency_t dependency;
 
-
-  SD_CHECK_INIT_DONE();
-  xbt_assert(src != NULL && dst != NULL, "Invalid parameter");
-
   dynar = src->tasks_after;
   length = xbt_dynar_length(dynar);
 
@@ -642,9 +670,6 @@ static void __SD_print_watch_points(SD_task_t task)
  */
 void SD_task_watch(SD_task_t task, e_SD_task_state_t state)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-
   if (state & SD_NOT_SCHEDULED)
     THROWF(arg_error, 0,
            "Cannot add a watch point for state SD_NOT_SCHEDULED");
@@ -662,8 +687,6 @@ 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_assert(task != NULL, "Invalid parameter");
   xbt_assert(state != SD_NOT_SCHEDULED,
               "SimDag error: Cannot have a watch point for state SD_NOT_SCHEDULED");
 
@@ -693,9 +716,7 @@ double SD_task_get_execution_time(SD_task_t task,
 {
   double time, max_time = 0.0;
   int i, j;
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL && workstation_nb > 0
-              && workstation_list != NULL, "Invalid parameter");
+  xbt_assert(workstation_nb > 0, "Invalid parameter");
 
   /* the task execution time is the maximum execution time of the parallel tasks */
 
@@ -725,8 +746,6 @@ double SD_task_get_execution_time(SD_task_t task,
 
 static XBT_INLINE void SD_task_do_schedule(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-
   if (!__SD_task_is_not_scheduled(task) && !__SD_task_is_schedulable(task))
     THROWF(arg_error, 0, "Task '%s' has already been scheduled",
            SD_task_get_name(task));
@@ -746,7 +765,7 @@ static XBT_INLINE void SD_task_do_schedule(SD_task_t task)
  * 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_count 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
@@ -808,9 +827,6 @@ void SD_task_schedule(SD_task_t task, int workstation_count,
  */
 void SD_task_unschedule(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-
   if (task->state_set != sd_global->scheduled_task_set &&
       task->state_set != sd_global->runnable_task_set &&
       task->state_set != sd_global->running_task_set &&
@@ -839,7 +855,6 @@ void SD_task_unschedule(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_runnable(task)
       && !__SD_task_is_in_fifo(task))
     THROWF(arg_error, 0,
@@ -861,11 +876,9 @@ void __SD_task_really_run(SD_task_t task)
   int i;
   void **surf_workstations;
 
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   xbt_assert(__SD_task_is_runnable_or_in_fifo(task),
               "Task '%s' is not runnable or in a fifo! Task state: %d",
-              SD_task_get_name(task), SD_task_get_state(task));
+             SD_task_get_name(task), (int)SD_task_get_state(task));
   xbt_assert(task->workstation_list != NULL,
               "Task '%s': workstation_list is NULL!",
               SD_task_get_name(task));
@@ -967,7 +980,7 @@ void __SD_task_really_run(SD_task_t task)
   __SD_task_destroy_scheduling_data(task);      /* now the scheduling data are not useful anymore */
   __SD_task_set_state(task, SD_RUNNING);
   xbt_assert(__SD_task_is_running(task), "Bad state of task '%s': %d",
-              SD_task_get_name(task), SD_task_get_state(task));
+             SD_task_get_name(task), (int)SD_task_get_state(task));
 
 }
 
@@ -984,11 +997,9 @@ int __SD_task_try_to_run(SD_task_t task)
   int i;
   SD_workstation_t workstation;
 
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   xbt_assert(__SD_task_is_runnable(task),
               "Task '%s' is not runnable! Task state: %d",
-              SD_task_get_name(task), SD_task_get_state(task));
+             SD_task_get_name(task), (int)SD_task_get_state(task));
 
 
   for (i = 0; i < task->workstation_nb; i++) {
@@ -1010,7 +1021,7 @@ int __SD_task_try_to_run(SD_task_t task)
     }
     __SD_task_set_state(task, SD_IN_FIFO);
     xbt_assert(__SD_task_is_in_fifo(task), "Bad state of task '%s': %d",
-                SD_task_get_name(task), SD_task_get_state(task));
+               SD_task_get_name(task), (int)SD_task_get_state(task));
     XBT_DEBUG("Task '%s' state is now SD_IN_FIFO", SD_task_get_name(task));
   } else {
     __SD_task_really_run(task);
@@ -1034,11 +1045,9 @@ void __SD_task_just_done(SD_task_t task)
   SD_task_t *candidates;
   int can_start = 1;
 
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   xbt_assert(__SD_task_is_running(task),
               "The task must be running! Task state: %d",
-              SD_task_get_state(task));
+              (int)SD_task_get_state(task));
   xbt_assert(task->workstation_list != NULL,
               "Task '%s': workstation_list is NULL!",
               SD_task_get_name(task));
@@ -1057,7 +1066,7 @@ void __SD_task_just_done(SD_task_t task)
   for (i = 0; i < task->workstation_nb; i++) {
     workstation = task->workstation_list[i];
     XBT_DEBUG("Workstation '%s': access_mode = %d",
-           SD_workstation_get_name(workstation), workstation->access_mode);
+              SD_workstation_get_name(workstation), (int)workstation->access_mode);
     if (workstation->access_mode == SD_WORKSTATION_SEQUENTIAL_ACCESS) {
       xbt_assert(workstation->task_fifo != NULL,
                   "Workstation '%s' has sequential access but no fifo!",
@@ -1080,7 +1089,7 @@ void __SD_task_just_done(SD_task_t task)
         xbt_assert(__SD_task_is_in_fifo(candidate),
                     "Bad state of candidate '%s': %d",
                     SD_task_get_name(candidate),
-                    SD_task_get_state(candidate));
+                    (int)SD_task_get_state(candidate));
       }
 
       XBT_DEBUG("Candidate in fifo: %p", candidate);
@@ -1119,7 +1128,7 @@ void __SD_task_just_done(SD_task_t task)
 
     xbt_assert(__SD_task_is_in_fifo(candidate),
                 "Bad state of candidate '%s': %d",
-                SD_task_get_name(candidate), SD_task_get_state(candidate));
+               SD_task_get_name(candidate), (int)SD_task_get_state(candidate));
 
     for (j = 0; j < candidate->workstation_nb && can_start; j++) {
       workstation = candidate->workstation_list[j];
@@ -1153,7 +1162,7 @@ void __SD_task_just_done(SD_task_t task)
 
       /* finally execute the task */
       XBT_DEBUG("Task '%s' state: %d", SD_task_get_name(candidate),
-             SD_task_get_state(candidate));
+             (int)SD_task_get_state(candidate));
       __SD_task_really_run(candidate);
 
       XBT_DEBUG
@@ -1163,7 +1172,7 @@ void __SD_task_just_done(SD_task_t task)
       xbt_assert(__SD_task_is_running(candidate),
                   "Bad state of task '%s': %d",
                   SD_task_get_name(candidate),
-                  SD_task_get_state(candidate));
+                 (int)SD_task_get_state(candidate));
       XBT_DEBUG("Okay, the task is running.");
 
     }                           /* can start */
@@ -1180,12 +1189,12 @@ 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) {
+  while (!xbt_dynar_is_empty(task->tasks_before)) {
     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) {
+  while (!xbt_dynar_is_empty(task->tasks_after)) {
     xbt_dynar_get_cpy(task->tasks_after, 0, &dependency);
     SD_task_dependency_remove(dependency->src, dependency->dst);
   }
@@ -1201,8 +1210,6 @@ static void __SD_task_remove_dependencies(SD_task_t task)
  */
 double SD_task_get_start_time(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
   if (task->surf_action)
     return surf_workstation_model->
         action_get_start_time(task->surf_action);
@@ -1223,9 +1230,6 @@ double SD_task_get_start_time(SD_task_t task)
  */
 double SD_task_get_finish_time(SD_task_t task)
 {
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-
   if (task->surf_action)        /* should never happen as actions are destroyed right after their completion */
     return surf_workstation_model->
         action_get_finish_time(task->surf_action);
@@ -1233,56 +1237,6 @@ double SD_task_get_finish_time(SD_task_t task)
     return task->finish_time;
 }
 
-/**
- * \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)
-{
-  SD_CHECK_INIT_DONE();
-  xbt_assert(task != NULL, "Invalid parameter");
-
-  XBT_DEBUG("Destroying task %s...", SD_task_get_name(task));
-
-  __SD_task_remove_dependencies(task);
-  /* if the task was scheduled or runnable we have to free the scheduling parameters */
-  if (__SD_task_is_scheduled_or_runnable(task))
-    __SD_task_destroy_scheduling_data(task);
-  xbt_swag_remove(task, task->state_set);
-
-  if (task->name != NULL)
-    xbt_free(task->name);
-
-  if (task->surf_action != NULL)
-    surf_workstation_model->action_unref(task->surf_action);
-
-  if (task->workstation_list != NULL)
-    xbt_free(task->workstation_list);
-
-  if (task->communication_amount)
-    xbt_free(task->communication_amount);
-
-  if (task->computation_amount)
-    xbt_free(task->computation_amount);
-
-#ifdef HAVE_TRACING
-  TRACE_sd_task_destroy(task);
-#endif
-
-  xbt_dynar_free(&task->tasks_before);
-  xbt_dynar_free(&task->tasks_after);
-  xbt_free(task);
-
-  sd_global->task_number--;
-
-  XBT_DEBUG("Task destroyed.");
-}
-
-
 static XBT_INLINE SD_task_t SD_task_create_sized(const char *name,
                                                  void *data, double amount,
                                                  int ws_count)
@@ -1364,7 +1318,7 @@ void SD_task_schedulev(SD_task_t task, int count,
   switch (task->kind) {
   case SD_TASK_COMM_E2E:
   case SD_TASK_COMP_SEQ:
-    xbt_assert(task->workstation_nb == count);
+    xbt_assert(task->workstation_nb == count,"Got %d locations, but were expecting %d locations",count,task->workstation_nb);
     for (i = 0; i < count; i++)
       task->workstation_list[i] = list[i];
     SD_task_do_schedule(task);