Removed an unnecessary test of neighbourhood in iact_pair()

examples/test_bh.c

@@ -820,27 +820,27 @@ void iact_pair(struct cell *ci, struct cell *cj) {
     error("The impossible has happened: pair interaction between a cell and "
           "itself.");
 
-#endif
-
   /* Are the cells direct neighbours? */
-  if (are_neighbours(ci, cj)) {
+  if (!are_neighbours(ci, cj)) 
+    error("Non-neighbouring cells !");
 
-    /* Are both cells split ? */
-    if (ci->split && cj->split) {
-
-      /* Let's split both cells and build all possible pairs */
-      for (cp = ci->firstchild; cp != ci->sibling; cp = cp->sibling) {
-        for (cps = cj->firstchild; cps != cj->sibling; cps = cps->sibling) {
+#endif
 
-          /* If the cells are neighbours, recurse. */
-          if (are_neighbours(cp, cps)) {
-            iact_pair(cp, cps);
-          }
-        }
+  /* Are both cells split ? */
+  if (ci->split && cj->split) {
+
+    /* Let's split both cells and build all possible pairs */
+    for (cp = ci->firstchild; cp != ci->sibling; cp = cp->sibling) {
+      for (cps = cj->firstchild; cps != cj->sibling; cps = cps->sibling) {
+	
+	/* If the cells are neighbours, recurse. */
+	if (are_neighbours(cp, cps)) {
+	  iact_pair(cp, cps);
+	}
       }
-    } else {/* Otherwise, compute the interactions at this level directly. */
-      iact_pair_direct(ci, cj);
     }
+  } else {/* Otherwise, compute the interactions at this level directly. */
+    iact_pair_direct(ci, cj);
   }
 }