Fix singleton operation

OpenPMIx fills in a variety of info when it detects that we are in
singleton mode. Best way of detecting it is to look for the "singleton"
at the beginning of the returned nspace.

Make the modex recvs optional so we don't bounce up to the server and
then to the host trying to retrieve job-level info that must be given to
us at job start.

Signed-off-by: Ralph Castain <rhc@pmix.org>

ompi/runtime/ompi_rte.c

@@ -543,6 +543,10 @@ int ompi_rte_init(int *pargc, char ***pargv)
         opal_show_help("help-mpi-runtime.txt", "no-pmi", true, PMIx_Error_string(ret));
         return OPAL_ERR_SILENT;
     }
+    /* if our nspace starts with "singleton", then we are a singleton */
+    if (0 == strncmp(myprocid.nspace, "singleton", strlen("singleton"))) {
+        ompi_singleton = true;
+    }
 
     /* setup the process name fields - also registers the new nspace */
     OPAL_PMIX_CONVERT_PROCT(rc, &pname, &myprocid);
@@ -566,20 +570,19 @@ int ompi_rte_init(int *pargc, char ***pargv)
     ompi_process_info.nodename = opal_process_info.nodename;
 
     /* get our local rank from PMI */
-    OPAL_MODEX_RECV_VALUE(rc, PMIX_LOCAL_RANK,
-                          &pmix_process_info.my_name, &u16ptr, PMIX_UINT16);
+    OPAL_MODEX_RECV_VALUE_OPTIONAL(rc, PMIX_LOCAL_RANK,
+                                   &pmix_process_info.my_name, &u16ptr, PMIX_UINT16);
     if (PMIX_SUCCESS != rc) {
-        /* assume we are a singleton */
-        u16 = 0;
-        ompi_singleton = true;
+        ret = opal_pmix_convert_status(rc);
+        error = "local rank";
+        goto error;
     }
     pmix_process_info.my_local_rank = u16;
 
     /* get our node rank from PMI */
-    OPAL_MODEX_RECV_VALUE(rc, PMIX_NODE_RANK,
-                          &pmix_process_info.my_name, &u16ptr, PMIX_UINT16);
+    OPAL_MODEX_RECV_VALUE_OPTIONAL(rc, PMIX_NODE_RANK,
+                                   &pmix_process_info.my_name, &u16ptr, PMIX_UINT16);
     if (PMIX_SUCCESS != rc) {
-        /* assume we are a singleton */
         u16 = 0;
     }
     pmix_process_info.my_node_rank = u16;
@@ -587,11 +590,12 @@ int ompi_rte_init(int *pargc, char ***pargv)
     /* get job size */
     pname.jobid = pmix_process_info.my_name.jobid;
     pname.vpid = OPAL_VPID_WILDCARD;
-    OPAL_MODEX_RECV_VALUE(rc, PMIX_JOB_SIZE,
-                          &pname, &u32ptr, PMIX_UINT32);
+    OPAL_MODEX_RECV_VALUE_OPTIONAL(rc, PMIX_JOB_SIZE,
+                                   &pname, &u32ptr, PMIX_UINT32);
     if (PMIX_SUCCESS != rc) {
-        /* assume we are a singleton */
-        u32 = 1;
+        ret = opal_pmix_convert_status(rc);
+        error = "job size";
+        goto error;
     }
     pmix_process_info.num_procs = u32;
 
@@ -620,12 +624,14 @@ int ompi_rte_init(int *pargc, char ***pargv)
 
     /* get the number of local peers - required for wireup of
      * shared memory BTL */
-    OPAL_MODEX_RECV_VALUE(rc, PMIX_LOCAL_SIZE,
-                          &pname, &u32ptr, PMIX_UINT32);
+    OPAL_MODEX_RECV_VALUE_OPTIONAL(rc, PMIX_LOCAL_SIZE,
+                                   &pname, &u32ptr, PMIX_UINT32);
     if (PMIX_SUCCESS == rc) {
         pmix_process_info.num_local_peers = u32 - 1;  // want number besides ourselves
     } else {
-        pmix_process_info.num_local_peers = 0;
+        ret = opal_pmix_convert_status(rc);
+        error = "local size";
+        goto error;
     }
 
     /* setup transport keys in case the MPI layer needs them -
@@ -711,7 +717,9 @@ int ompi_rte_init(int *pargc, char ***pargv)
             peers = opal_argv_split(val, ',');
             free(val);
         } else {
-            peers = NULL;
+            ret = opal_pmix_convert_status(rc);
+            error = "local peers";
+            goto error;
         }
     } else {
         peers = NULL;