Corrected documentation and removed MPI exception.

src/active.h

@@ -30,11 +30,9 @@
 /**
  * @brief Check that a cell been drifted to the current time.
  *
- * Only used for debugging. Calls error() if the cell has not
- * been drifted. Does nothing if SWIFT_DEBUG_CHECKS is not defined.
- *
  * @param c The #cell.
  * @param e The #engine containing information about the current time.
+ * @return 1 if the #cell has been drifted to the current time, 0 otherwise.
  */
 __attribute__((always_inline)) INLINE static int cell_is_drifted(
     const struct cell *c, const struct engine *e) {
@@ -55,6 +53,7 @@ __attribute__((always_inline)) INLINE static int cell_is_drifted(
  *
  * @param c The #cell.
  * @param e The #engine containing information about the current time.
+ * @param 1 if the #cell contains at least an active particle, 0 otherwise.
  */
 __attribute__((always_inline)) INLINE static int cell_is_active(
     const struct cell *c, const struct engine *e) {
@@ -73,6 +72,7 @@ __attribute__((always_inline)) INLINE static int cell_is_active(
  *
  * @param c The #cell.
  * @param e The #engine containing information about the current time.
+ * @param 1 if all particles in a #cell are active, 0 otherwise.
  */
 __attribute__((always_inline)) INLINE static int cell_is_all_active(
     const struct cell *c, const struct engine *e) {
@@ -91,6 +91,7 @@ __attribute__((always_inline)) INLINE static int cell_is_all_active(
  *
  * @param p The #part.
  * @param e The #engine containing information about the current time.
+ * @return 1 if the #part is active, 0 otherwise.
  */
 __attribute__((always_inline)) INLINE static int part_is_active(
     const struct part *p, const struct engine *e) {
@@ -109,6 +110,7 @@ __attribute__((always_inline)) INLINE static int part_is_active(
  *
  * @param gp The #gpart.
  * @param e The #engine containing information about the current time.
+ * @return 1 if the #gpart is active, 0 otherwise.
  */
 __attribute__((always_inline)) INLINE static int gpart_is_active(
     const struct gpart *gp, const struct engine *e) {

src/engine.c

@@ -2684,7 +2684,7 @@ int engine_is_done(struct engine *e) {
 }
 
 /**
- * @brief Drift particles using the current engine drift policy.
+ * @brief Unskip all the tasks that act on active cells at this time.
  *
  * @param e The #engine.
  */
@@ -2699,6 +2699,11 @@ void engine_unskip(struct engine *e) {
             clocks_getunit());
 }
 
+/**
+ * @brief Drift *all* particles forward to the current time.
+ *
+ * @param e The #engine.
+ */
 void engine_drift_all(struct engine *e) {
 
   const ticks tic = getticks();

src/runner.c

@@ -757,7 +757,7 @@ static void runner_do_unskip(struct cell *c, struct engine *e) {
     if (forcerebuild) atomic_inc(&e->forcerebuild);
   }
 
-  /* Not drifting, but may still need to recurse for task un-skipping. */
+  /* Recurse */
   if (c->split) {
     for (int k = 0; k < 8; k++) {
       if (c->progeny[k] != NULL) {
@@ -783,11 +783,7 @@ void runner_do_unskip_mapper(void *map_data, int num_elements,
 
   for (int ind = 0; ind < num_elements; ind++) {
     struct cell *c = &cells[ind];
-#ifdef WITH_MPI
-    if (c != NULL) runner_do_unskip(c, e);
-#else
     if (c != NULL) runner_do_unskip(c, e);
-#endif
   }
 }
 /**