sessions:improve error messages

Improve error message when an application is using
a PML that doesn't support excid, and hence sessions
related functions
- MPI_Comm_from_group
- MPI_Intercomm_create_from_groups

Example:

--------------------------------------------------------------------------
Your application has invoked an MPI function that is not supported in
this environment.

  MPI function: MPI_Comm_from_group/MPI_Intercomm_from_groups
  Reason:       The PML being used - ucx - does not support MPI sessions related features
--------------------------------------------------------------------------

Signed-off-by: Howard Pritchard <[email protected]>

Author: hppritcha

ompi/communicator/Makefile.am

@@ -39,3 +39,4 @@ lib@OMPI_LIBMPI_NAME@_la_SOURCES += \
 	communicator/ft/comm_ft.c communicator/ft/comm_ft_reliable_bcast.c communicator/ft/comm_ft_propagator.c communicator/ft/comm_ft_detector.c communicator/ft/comm_ft_revoke.c
 endif # WANT_FT_MPI
 
+dist_ompidata_DATA += communicator/help-comm.txt

ompi/communicator/comm_cid.c

@@ -39,6 +39,7 @@
 #include "opal/mca/pmix/base/base.h"
 #include "opal/mca/pmix/pmix-internal.h"
 #include "opal/util/printf.h"
+#include "opal/util/show_help.h"
 
 #include "ompi/proc/proc.h"
 #include "ompi/communicator/communicator.h"
@@ -48,6 +49,7 @@
 #include "opal/class/opal_list.h"
 #include "ompi/mca/pml/pml.h"
 #include "ompi/runtime/ompi_rte.h"
+#include "ompi/mca/pml/base/base.h"
 #include "ompi/mca/coll/base/base.h"
 #include "ompi/request/request.h"
 #include "ompi/runtime/mpiruntime.h"
@@ -428,8 +430,19 @@ int ompi_comm_nextcid_nb (ompi_communicator_t *newcomm, ompi_communicator_t *com
 
     /* old CID algorighm */
 
+    /* if we got here and comm is NULL then that means the app is  invoking MPI-4 Sessions or later
+       functions but the pml does not support these functions so return not supported */
     if (NULL == comm) {
-        return OMPI_ERR_BAD_PARAM;
+       char msg_string[1024];
+       sprintf(msg_string,"The PML being used - %s - does not support MPI sessions related features", 
+               mca_pml_base_selected_component.pmlm_version.mca_component_name);
+       opal_show_help("help-comm.txt",
+                      "MPI function not supported",
+                      true,
+                      "MPI_Comm_from_group/MPI_Intercomm_from_groups",
+                      msg_string);
+
+        return MPI_ERR_UNSUPPORTED_OPERATION;
     }
 
     newcomm->c_flags |= OMPI_COMM_GLOBAL_INDEX;

ompi/mpi/c/comm_create_from_group.c

@@ -83,5 +83,10 @@ 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,
                                       (ompi_communicator_t **) newcomm);
-    OMPI_ERRHANDLER_RETURN (rc, *newcomm, rc, FUNC_NAME);
+    if (MPI_SUCCESS != rc) {
+        return ompi_errhandler_invoke (errhandler, MPI_COMM_NULL, errhandler->eh_mpi_object_type,
+                                       rc, FUNC_NAME);
+    }
+
+    return rc;
 }

ompi/mpi/c/intercomm_create_from_groups.c

@@ -85,6 +85,11 @@ int MPI_Intercomm_create_from_groups (MPI_Group local_group, int local_leader, M
     rc = ompi_intercomm_create_from_groups (local_group, local_leader, remote_group, remote_leader, tag,
                                             &info->super, errhandler, newintercomm);
 
-    OMPI_ERRHANDLER_RETURN (rc, MPI_COMM_SELF, rc, FUNC_NAME);
+    if (MPI_SUCCESS != rc) {
+        return ompi_errhandler_invoke (errhandler, MPI_COMM_NULL, errhandler->eh_mpi_object_type,
+                                       rc, FUNC_NAME);
+    }
+
+    return rc;
 }