Add protection against a bozo case where we could end up in an infinite loop while calculating ranks

This commit was SVN r25491.

orte/mca/rmaps/base/help-orte-rmaps-base.txt

@@ -185,3 +185,9 @@ Unknown binding level:
 
   Target:  %s
   Cache level:  %u
+#
+[ranking-error]
+An infinite loop condition has been detected in the ranking
+code when computing ranks %s. This indicates a problem
+in the mapper. Please refer the problem to the attention
+of the OMPI developers.

orte/mca/rmaps/base/rmaps_base_ranking.c

@@ -381,7 +381,8 @@ int orte_rmaps_base_compute_vpids(orte_job_t *jdata)
     orte_node_t *node;
     orte_proc_t *proc, *ptr;
     int rc;
-    
+    bool added_one=false;
+
     map = jdata->map;
     
     if (ORTE_RANK_BY_NODE == ORTE_GET_RANKING_POLICY(map->ranking) ||
@@ -395,6 +396,7 @@ int orte_rmaps_base_compute_vpids(orte_job_t *jdata)
         cnt=0;
         vpid=0;
         while (cnt < jdata->num_procs) {
+            added_one = false;
             for (i=0; i < map->nodes->size; i++) {
                 if (NULL == (node = (orte_node_t*)opal_pointer_array_get_item(map->nodes, i))) {
                     continue;
@@ -408,8 +410,7 @@ int orte_rmaps_base_compute_vpids(orte_job_t *jdata)
                         continue;
                     }
                     if (ORTE_VPID_INVALID != proc->name.vpid) {
-                        /* vpid was already assigned, probably by the
-                         * round-robin mapper. Some mappers require that
+                        /* vpid was already assigned. Some mappers require that
                          * we insert the proc into the jdata->procs
                          * array, while others will have already done it - so check and
                          * do the operation if required
@@ -423,6 +424,7 @@ int orte_rmaps_base_compute_vpids(orte_job_t *jdata)
                              * it in our loop - otherwise don't as we would be
                              * double counting
                              */
+                            added_one = true;
                             cnt++;
                         }
                         continue;
@@ -444,8 +446,17 @@ int orte_rmaps_base_compute_vpids(orte_job_t *jdata)
                         return rc;
                     }
                     cnt++;
+                    added_one = true;
                     break;  /* move on to next node */
-                }
+                }                
+            }
+            /* it should be impossible, but check to see if there was nothing
+             * added during this pass and error out if not
+             */
+            if (!added_one) {
+                orte_show_help("help-orte-rmaps-base.txt", "orte-rmaps-base:ranking-error",
+                               true, "bynode");
+                return ORTE_ERR_SILENT;
             }
         }
         return ORTE_SUCCESS;