Merge pull request #12960 from hppritcha/fix_for_issue10895

comm: beef up use of PMIx_Group_construct

Author: hppritcha

ompi/communicator/comm.c

@@ -1784,22 +1784,22 @@ int ompi_intercomm_create_from_groups (ompi_group_t *local_group, int local_lead
                 leader_procs[1] = tmp;
             }
 
-            /* create a unique tag for allocating the leader communicator. we can eliminate this step
-             * if we take a CID from the newly allocated block belonging to local_comm. this is
-             * a note to make this change at a later time. */
-            opal_asprintf (&sub_tag, "%s-OMPIi-LC", tag);
-            if (OPAL_UNLIKELY(NULL == sub_tag)) {
-                ompi_comm_free (&local_comm);
+            leader_group = ompi_group_allocate_plist_w_procs (NULL, leader_procs, 2);
+            ompi_set_group_rank (leader_group, my_proc);
+            if (OPAL_UNLIKELY(NULL == leader_group)) {
                 free(leader_procs);
+                ompi_comm_free (&local_comm);
                 return OMPI_ERR_OUT_OF_RESOURCE;
             }
 
-            leader_group = ompi_group_allocate_plist_w_procs (NULL, leader_procs, 2);
-            ompi_set_group_rank (leader_group, my_proc);
-            if (OPAL_UNLIKELY(NULL == leader_group)) {
-                free (sub_tag);
+            /* create a unique tag for allocating the leader communicator. we can eliminate this step
+             * if we take a CID from the newly allocated block belonging to local_comm. this is
+             * a note to make this change at a later time. */
+            opal_asprintf (&sub_tag, "%s-OMPIi-LC-%s", tag, OPAL_NAME_PRINT(ompi_group_get_proc_name (leader_group, 0)));
+            if (OPAL_UNLIKELY(NULL == sub_tag)) {
                 free(leader_procs);
                 ompi_comm_free (&local_comm);
+                OBJ_RELEASE(leader_group);
                 return OMPI_ERR_OUT_OF_RESOURCE;
             }
 
@@ -1809,6 +1809,7 @@ int ompi_intercomm_create_from_groups (ompi_group_t *local_group, int local_lead
             rc = ompi_comm_create_from_group (leader_group, sub_tag, info, errhandler, &leader_comm);
             OBJ_RELEASE(leader_group);
             free (sub_tag);
+            sub_tag = NULL;
             if (OPAL_UNLIKELY(OMPI_SUCCESS != rc)) {
                 free(leader_procs);
                 ompi_comm_free (&local_comm);
@@ -1864,7 +1865,16 @@ int ompi_intercomm_create_from_groups (ompi_group_t *local_group, int local_lead
         return rc;
     }
 
-    rc = ompi_comm_nextcid (newcomp, NULL, NULL, (void *) tag, NULL, false, OMPI_COMM_CID_GROUP_NEW);
+    /*
+     * append the pmix CONTEXT_ID obtained when creating the leader comm as discriminator
+     */
+    opal_asprintf (&sub_tag, "%s-%ld", tag, data[1]);
+    if (OPAL_UNLIKELY(NULL == sub_tag)) {
+        return OMPI_ERR_OUT_OF_RESOURCE;
+    }
+
+    rc = ompi_comm_nextcid (newcomp, NULL, NULL, (void *) sub_tag, NULL, false, OMPI_COMM_CID_GROUP_NEW);
+    free (sub_tag);
     if ( OMPI_SUCCESS != rc ) {
         OBJ_RELEASE(newcomp);
         return rc;

ompi/mpi/c/comm_create_from_group.c

@@ -46,6 +46,7 @@ static const char FUNC_NAME[] = "MPI_Comm_create_from_group";
 int MPI_Comm_create_from_group (MPI_Group group, const char *tag, MPI_Info info, MPI_Errhandler errhandler,
                                 MPI_Comm *newcomm) {
     int rc;
+    char *pmix_group_tag = NULL;
 
     MEMCHECKER(
         memchecker_comm(comm);
@@ -89,8 +90,22 @@ int MPI_Comm_create_from_group (MPI_Group group, const char *tag, MPI_Info info,
     }
 
 
-    rc = ompi_comm_create_from_group ((ompi_group_t *) group, tag, &info->super, errhandler,
+    /*
+     * we use PMIx group operations to implement comm/intercomm create from group/groups.
+     * PMIx group constructors require a unique tag across the processes using the same
+     * PMIx server.  This is not equivalent to the uniqueness requirements of the tag argument
+     * to MPI_Comm_create_from_group and MPI_Intercomm_create_from_groups, hence an
+     * additional discriminator needs to be added to the user supplied tag argument.
+     */
+    opal_asprintf (&pmix_group_tag, "%s-%s.%d", tag, OPAL_NAME_PRINT(ompi_group_get_proc_name (group, 0)),
+                   ompi_group_size(group));
+    if (OPAL_UNLIKELY(NULL == pmix_group_tag)) {
+        return OMPI_ERR_OUT_OF_RESOURCE;
+    }
+
+    rc = ompi_comm_create_from_group ((ompi_group_t *) group, pmix_group_tag, &info->super, errhandler,
                                       (ompi_communicator_t **) newcomm);
+    free(pmix_group_tag);
     if (MPI_SUCCESS != rc) {
         return ompi_errhandler_invoke (errhandler, MPI_COMM_NULL, errhandler->eh_mpi_object_type,
                                        rc, FUNC_NAME);