Print more information when returning an error message for unsorted particles in DOPAIR1()

src/cell.c

@@ -1791,7 +1791,9 @@ int cell_unskip_tasks(struct cell *c, struct scheduler *s) {
           if (l == NULL) error("Missing link to send_ti task.");
           scheduler_activate(s, l->t);
         }
-      } else if (t->type == task_type_pair) {
+      } 
+
+      else if (t->type == task_type_pair) { /* ci and cj on same node */
         scheduler_activate(s, ci->drift_part);
         scheduler_activate(s, cj->drift_part);
       }

src/engine.c

@@ -2717,7 +2717,7 @@ void engine_marktasks_mapper(void *map_data, int num_elements,
           scheduler_activate(s, l->t);
         }
 
-      } else if (t->type == task_type_pair) {
+      } else if (t->type == task_type_pair) { /* ci and cj on same node */
         scheduler_activate(s, ci->drift_part);
         scheduler_activate(s, cj->drift_part);
       }

src/runner_doiact.h

@@ -919,7 +919,7 @@ void DOPAIR1(struct runner *r, struct cell *ci, struct cell *cj, const int sid,
                     p->x[2] * runner_shift[sid][2];
     if (fabsf(d - sort_i[pid].d) - ci->dx_max_sort >
         1.0e-6 * max(fabsf(d), ci->dx_max_sort))
-      error("particle shift diff exceeds dx_max_sort.");
+      error("particle shift diff exceeds dx_max_sort in cell ci. ci->nodeID=%d cj->nodeID=%d d=%e sort_i[pid].d=%e ci->dx_max_sort=%e ci->dx_max_sort_old=%e", ci->nodeID, cj->nodeID, d, sort_i[pid].d, ci->dx_max_sort, ci->dx_max_sort_old);
   }
   for (int pjd = 0; pjd < cj->count; pjd++) {
     const struct part *p = &cj->parts[sort_j[pjd].i];
@@ -928,7 +928,7 @@ void DOPAIR1(struct runner *r, struct cell *ci, struct cell *cj, const int sid,
                     p->x[2] * runner_shift[sid][2];
     if (fabsf(d - sort_j[pjd].d) - cj->dx_max_sort >
         1.0e-6 * max(fabsf(d), cj->dx_max_sort))
-      error("particle shift diff exceeds dx_max_sort.");
+      error("particle shift diff exceeds dx_max_sort in cell cj. cj->nodeID=%d ci->nodeID=%d d=%e sort_j[pjd].d=%e cj->dx_max_sort=%e cj->dx_max_sort_old=%e", cj->nodeID, ci->nodeID, d, sort_j[pjd].d, cj->dx_max_sort, cj->dx_max_sort_old);
   }
 #endif /* SWIFT_DEBUG_CHECKS */