Fix bug in multiple BH mergers

src/runner_black_holes.c

@@ -306,9 +306,10 @@ void runner_do_bh_swallow(struct runner *r, struct cell *c, int timer) {
     }
   } else {
 
-    /* Loop over all the gas particles in the cell
+    /* Loop over all the BH particles in the cell
      * Note that the cell (and hence the bparts) may be local or foreign. */
     const size_t nr_cell_bparts = c->black_holes.count;
+
     for (size_t k = 0; k < nr_cell_bparts; k++) {
 
       /* Get a handle on the part. */
@@ -317,7 +318,7 @@ void runner_do_bh_swallow(struct runner *r, struct cell *c, int timer) {
       /* Ignore inhibited particles (they have already been removed!) */
       if (bpart_is_inhibited(cell_bp, e)) continue;
 
-      /* Get the ID of the black holes that will swallow this part */
+      /* Get the ID of the black holes that will swallow this bpart */
       const long long swallow_id =
           black_holes_get_bpart_swallow_id(&cell_bp->merger_data);
 
@@ -350,7 +351,21 @@ void runner_do_bh_swallow(struct runner *r, struct cell *c, int timer) {
              */
             lock_lock(&s->lock);
 
-            /* Swallow the gas particle (i.e. update the BH properties) */
+            /* If bpart is inhibited, it cannot do any swallowing */
+            if (bpart_is_inhibited(bp, e)) {
+              message("BH %lld inhibited -- DOES NOT swallow BH %lld", bp->id,
+                      cell_bp->id);
+
+              /* Pretend it was found */
+              found = 1;
+
+              if (lock_unlock(&s->lock) != 0)
+                error("Failed to unlock the space.");
+              break;
+            }
+
+            /* Swallow the BH particle (i.e. update the swallowing BH
+             * properties with the properties of cell_bp) */
             black_holes_swallow_bpart(bp, cell_bp, e->cosmology, e->time,
                                       with_cosmology, props);
 
@@ -360,12 +375,12 @@ void runner_do_bh_swallow(struct runner *r, struct cell *c, int timer) {
 
             message("BH %lld swallowing BH particle %lld", bp->id, cell_bp->id);
 
-            /* If the gas particle is local, remove it */
+            /* If the BH particle is local, remove it */
             if (c->nodeID == e->nodeID) {
 
               message("BH %lld removing BH particle %lld", bp->id, cell_bp->id);
 
-              /* Finally, remove the gas particle from the system
+              /* Finally, remove the BH particle from the system
                * Recall that the gpart associated with it is also removed
                * at the same time. */
               cell_remove_bpart(e, c, cell_bp);
@@ -414,6 +429,7 @@ void runner_do_bh_swallow(struct runner *r, struct cell *c, int timer) {
           error("BH particle %lld could not find BH %lld to be swallowed",
                 cell_bp->id, swallow_id);
         }
+
       } /* Part was flagged for swallowing */
     }   /* Loop over the parts */
   }     /* Cell is not split */