Added a debugging check to verify that the drift flags have been reset

src/cell.c

@@ -5466,6 +5466,43 @@ void cell_check_sort_flags(const struct cell *c) {
 #endif
 }
 
+/**
+ * @brief Checks that a cell and all its progenies have cleared their drift
+ * flags.
+ *
+ * Should only be used for debugging purposes.
+ *
+ * @param c The #cell to check.
+ */
+void cell_check_drift_flags(const struct cell *c) {
+
+#ifdef SWIFT_DEBUG_CHECKS
+  const int do_hydro_drift = cell_get_flag(c, cell_flag_do_hydro_drift);
+  const int do_hydro_sub_drift = cell_get_flag(c, cell_flag_do_hydro_sub_drift);
+  const int do_stars_sub_drift = cell_get_flag(c, cell_flag_do_stars_sub_drift);
+
+  if (do_hydro_drift)
+    error("cell %d has a hydro drift flag set. Node=%d depth=%d maxdepth=%d",
+          c->cellID, c->nodeID, c->depth, c->maxdepth);
+
+  if (do_hydro_sub_drift)
+    error(
+        "cell %d has a hydro sub_drift flag set. Node=%d depth=%d maxdepth=%d",
+        c->cellID, c->nodeID, c->depth, c->maxdepth);
+
+  if (do_stars_sub_drift)
+    error(
+        "cell %d has a stars sub_drift flag set. Node=%d depth=%d maxdepth=%d",
+        c->cellID, c->nodeID, c->depth, c->maxdepth);
+
+  if (c->split) {
+    for (int k = 0; k < 8; ++k) {
+      if (c->progeny[k] != NULL) cell_check_drift_flags(c->progeny[k]);
+    }
+  }
+#endif
+}
+
 /**
  * @brief Recursively update the pointer and counter for #spart after the
  * addition of a new particle.

src/cell.h

@@ -932,6 +932,7 @@ void cell_set_super_mapper(void *map_data, int num_elements, void *extra_data);
 void cell_check_spart_pos(const struct cell *c,
                           const struct spart *global_sparts);
 void cell_check_sort_flags(const struct cell *c);
+void cell_check_drift_flags(const struct cell *c);
 void cell_clear_stars_sort_flags(struct cell *c, const int unused_flags);
 void cell_clear_hydro_sort_flags(struct cell *c, const int unused_flags);
 int cell_has_tasks(struct cell *c);

src/engine.c

@@ -1814,6 +1814,7 @@ void engine_rebuild(struct engine *e, const int repartitioned,
       cell_check_foreign_multipole(&e->s->cells_top[e->s->local_cells_top[k]]);
   }
 
+  space_check_drift_flags(e->s);
   space_check_sort_flags(e->s);
 #endif
 
@@ -2704,6 +2705,7 @@ void engine_step(struct engine *e) {
 #ifdef SWIFT_DEBUG_CHECKS
   /* Make sure all woken-up particles have been processed */
   space_check_limiter(e->s);
+  space_check_drift_flags(e->s);
   space_check_sort_flags(e->s);
   space_check_swallow(e->s);
 #endif

src/space.c

@@ -5737,6 +5737,41 @@ void space_check_sort_flags(struct space *s) {
 #endif
 }
 
+void space_check_drift_flags_mapper(void *map_data, int nr_cells,
+                                    void *extra_data) {
+
+#ifdef SWIFT_DEBUG_CHECKS
+
+  const struct space *s = (struct space *)extra_data;
+  int *local_cells_top = map_data;
+
+  for (int ind = 0; ind < nr_cells; ++ind) {
+    const struct cell *c = &s->cells_top[local_cells_top[ind]];
+
+    cell_check_drift_flags(c);
+  }
+
+#endif
+}
+
+/**
+ * @brief Checks that all cells have cleared their drift flags.
+ *
+ * Should only be used for debugging purposes.
+ *
+ * @param s The #space to check.
+ */
+void space_check_drift_flags(struct space *s) {
+#ifdef SWIFT_DEBUG_CHECKS
+
+  threadpool_map(&s->e->threadpool, space_check_drift_flags_mapper,
+                 s->local_cells_with_tasks_top, s->nr_local_cells_with_tasks,
+                 sizeof(int), 1, s);
+#else
+  error("Calling debugging code without debugging flag activated.");
+#endif
+}
+
 /**
  * @brief Resets all the individual cell task counters to 0.
  *

src/space.h

@@ -374,6 +374,7 @@ void space_check_timesteps(const struct space *s);
 void space_check_limiter(struct space *s);
 void space_check_swallow(struct space *s);
 void space_check_sort_flags(struct space *s);
+void space_check_drift_flags(struct space *s);
 void space_replicate(struct space *s, int replicate, int verbose);
 void space_generate_gas(struct space *s, const struct cosmology *cosmo,
                         const int periodic, const int with_DM_background,