coll/han: disable alltoall for device buffers and MPI_IN_PLACE

The han alltoall algorithm was never intended for an in-place alltoall
and will crash if used in that configuration.  Additionally it is not
an efficient choice for device buffers.  Fall back to another
algorithm if either condition is met.

Signed-off-by: Luke Robison <lrbison@amazon.com>

Author: Luke Robison

ompi/mca/coll/han/coll_han_alltoall.c

@@ -69,6 +69,10 @@ int mca_coll_han_alltoall_using_smsc(
 {
 
     mca_coll_han_module_t *han_module = (mca_coll_han_module_t *)module;
+    opal_convertor_t convertor;
+    int send_needs_bounce, have_device_buffer;
+    size_t packed_size = 0;
+
 
     OPAL_OUTPUT_VERBOSE((90, mca_coll_han_component.han_output,
                             "Entering mca_coll_han_alltoall_using_smsc\n"));
@@ -82,6 +86,44 @@ int mca_coll_han_alltoall_using_smsc(
                                              comm, han_module->previous_alltoall_module);
     }
 
+    if (sbuf == MPI_IN_PLACE) {
+        /* This is not an in-place algorithm */
+        return han_module->previous_alltoall(sbuf, scount, sdtype, rbuf, rcount, rdtype,
+                                             comm, han_module->previous_alltoall_module);
+   }
+
+    OBJ_CONSTRUCT( &convertor, opal_convertor_t );
+    send_needs_bounce = 0;
+    have_device_buffer = 0;
+    /* get converter for copying to one of the leader ranks, and get packed size: */
+    opal_convertor_copy_and_prepare_for_send(ompi_mpi_local_convertor, &sdtype->super, scount, sbuf, 0, &convertor);
+    have_device_buffer |= opal_convertor_on_device(&convertor);
+    send_needs_bounce  |= opal_convertor_need_buffers(&convertor);
+    opal_convertor_cleanup(&convertor);
+
+    opal_convertor_copy_and_prepare_for_recv(ompi_mpi_local_convertor, &rdtype->super, rcount, rbuf, 0, &convertor);
+    have_device_buffer |= opal_convertor_on_device(&convertor);
+    send_needs_bounce  |= opal_convertor_need_buffers(&convertor);
+    opal_convertor_get_packed_size( &convertor, &packed_size );
+    opal_convertor_cleanup(&convertor);
+
+    if (have_device_buffer) {
+        /*
+        Although this algorithm is functional for device buffers, it requires an
+        extra copy through the bounce buffer that doesn't make it efficient.
+        Prefer another algorithm instead.
+
+        Note that Open MPI makes assumptions that if one rank uses a device
+        buffer in a collective, then all ranks will use device buffers, so there
+        is no need to communicate before taking this branch.
+        */
+        OBJ_DESTRUCT(&convertor);
+        return han_module->previous_alltoall(sbuf, scount, sdtype, rbuf, rcount, rdtype,
+                                             comm, han_module->previous_alltoall_module);
+    }
+
+
+
     /* Create the subcommunicators */
     if( OMPI_SUCCESS != mca_coll_han_comm_create_new(comm, han_module) ) {
         opal_output_verbose(1, mca_coll_han_component.han_output,
@@ -107,12 +149,11 @@ int mca_coll_han_alltoall_using_smsc(
                                              comm, han_module->previous_alltoall_module);
     }
 
-    int rc, send_needs_bounce, ii_push_data;
+    int rc, ii_push_data;
     size_t sndsize;
     MPI_Aint sextent, rextent, lb;
-    char *send_bounce;
-    opal_convertor_t convertor;
-    size_t packed_size = 0, packed_size_tmp;
+    char *send_bounce = NULL;
+    size_t packed_size_tmp;
     int use_isend;
     void *gather_buf_in[4];
     int up_rank;
@@ -140,22 +181,6 @@ int mca_coll_han_alltoall_using_smsc(
     }
     if (fanout > up_size) { fanout = up_size; }
 
-    OBJ_CONSTRUCT( &convertor, opal_convertor_t );
-
-
-    send_needs_bounce = 0;
-    /* get converter for copying to one of the leader ranks, and get packed size: */
-    opal_convertor_copy_and_prepare_for_send(ompi_mpi_local_convertor, &sdtype->super, scount, sbuf, 0, &convertor);
-    send_needs_bounce |= 0 != opal_convertor_on_device(&convertor);
-    send_needs_bounce |= opal_convertor_need_buffers(&convertor);
-    opal_convertor_cleanup(&convertor);
-
-    opal_convertor_copy_and_prepare_for_recv(ompi_mpi_local_convertor, &rdtype->super, rcount, rbuf, 0, &convertor);
-    send_needs_bounce |= 0 != opal_convertor_on_device(&convertor);
-    send_needs_bounce |= opal_convertor_need_buffers(&convertor);
-    opal_convertor_get_packed_size( &convertor, &packed_size );
-    opal_convertor_cleanup(&convertor);
-
     /*
       Because push-mode needs extra synchronizations, we'd like to avoid it,
       however it might be necessary: