coll: improve readability in MPIDI_Bcast_intra_composition_alpha

When the root is not the local node leader, the data needs to be sent
from the root to the local leader. Rewrite that part of code to make
it more clear.

src/mpid/ch4/src/ch4_coll_impl.h

@@ -233,35 +233,36 @@ MPL_STATIC_INLINE_PREFIX int MPIDI_Bcast_intra_composition_alpha(void *buffer, M
     MPI_Aint nbytes, recvd_size, type_size;
 #endif
 
-    if (comm->node_roots_comm == NULL && comm->rank == root) {
-        coll_ret = MPIC_Send(buffer, count, datatype, 0, MPIR_BCAST_TAG, comm->node_comm, errflag);
-        MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
-    }
-
-    if (comm->node_roots_comm != NULL && comm->rank != root &&
-        MPIR_Get_intranode_rank(comm, root) != -1) {
+    int intra_root = MPIR_Get_intranode_rank(comm, root);
+    if (intra_root != -1 && intra_root != 0) {
+        /* root send message to local leader (node_comm rank 0) */
+        if (comm->rank == root) {
+            coll_ret = MPIC_Send(buffer, count, datatype, 0, MPIR_BCAST_TAG, comm->node_comm, errflag);
+            MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
+        } else {
 #ifndef HAVE_ERROR_CHECKING
-        coll_ret =
-            MPIC_Recv(buffer, count, datatype, MPIR_Get_intranode_rank(comm, root), MPIR_BCAST_TAG,
-                      comm->node_comm, MPI_STATUS_IGNORE);
-        MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
+            coll_ret =
+                MPIC_Recv(buffer, count, datatype, MPIR_Get_intranode_rank(comm, root), MPIR_BCAST_TAG,
+                        comm->node_comm, MPI_STATUS_IGNORE);
+            MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
 #else
-        coll_ret =
-            MPIC_Recv(buffer, count, datatype, MPIR_Get_intranode_rank(comm, root), MPIR_BCAST_TAG,
-                      comm->node_comm, &status);
-        MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
-
-        MPIR_Datatype_get_size_macro(datatype, type_size);
-        nbytes = type_size * count;
-        /* check that we received as much as we expected */
-        MPIR_Get_count_impl(&status, MPI_BYTE, &recvd_size);
-        if (recvd_size != nbytes) {
-            MPIR_ERR_SET2(coll_ret, MPI_ERR_OTHER,
-                          "**collective_size_mismatch",
-                          "**collective_size_mismatch %d %d", recvd_size, nbytes);
+            coll_ret =
+                MPIC_Recv(buffer, count, datatype, MPIR_Get_intranode_rank(comm, root), MPIR_BCAST_TAG,
+                        comm->node_comm, &status);
             MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
-        }
+
+            MPIR_Datatype_get_size_macro(datatype, type_size);
+            nbytes = type_size * count;
+            /* check that we received as much as we expected */
+            MPIR_Get_count_impl(&status, MPI_BYTE, &recvd_size);
+            if (recvd_size != nbytes) {
+                MPIR_ERR_SET2(coll_ret, MPI_ERR_OTHER,
+                            "**collective_size_mismatch",
+                            "**collective_size_mismatch %d %d", recvd_size, nbytes);
+                MPIR_ERR_COLL_CHECKANDCONT(coll_ret, errflag, mpi_errno);
+            }
 #endif
+        }
     }
 
     MPIR_GPU_query_pointer_attr(buffer, &attr);