we only need ti_sorted in debug mode.

src/cell.h

@@ -239,9 +239,6 @@ struct cell {
   /*! Maximum beginning of (integer) time step in this cell. */
   integertime_t ti_beg_max;
 
-  /*! Last (integer) time the cell's sort arrays were updated. */
-  integertime_t ti_sort;
-
   /*! Last (integer) time the cell's part were drifted forward in time. */
   integertime_t ti_old_part;
 
@@ -347,6 +344,9 @@ struct cell {
   char do_sub_sort;
 
 #ifdef SWIFT_DEBUG_CHECKS
+  /*! Last (integer) time the cell's sort arrays were updated. */
+  integertime_t ti_sort;
+
   /*! The list of tasks that have been executed on this cell */
   char tasks_executed[64];
 

src/runner.c

@@ -355,11 +355,11 @@ void runner_do_sort(struct runner *r, struct cell *c, int flags, int cleanup,
        finger = finger->parent) {
     if (finger->sorted & ~c->sorted) error("Inconsistent sort flags (upward).");
   }
-#endif
 
   /* Update the sort timer which represents the last time the sorts
      were re-set. */
   if (c->sorted == 0) c->ti_sort = r->e->ti_current;
+#endif
 
   /* start by allocating the entry arrays. */
   if (c->sort == NULL) {