add some comments and make generated tests compile

scripts/devel/Template.py

@@ -38,16 +38,16 @@ int main(int argc, char **argv) {
   int rank = -1;
 
   MPI_Init(&argc, &argv);
-  @{mpi_init}@ 
+  // @{mpi_init}@ // One could also templte this 
   MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
   MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-   @{num_ranks_check}@ 
+   //@{num_ranks_check}@  // One could also templte this
   if (nprocs < 2)
     printf("MBI ERROR: This test needs at least 2 processes to produce a bug!\\n");
 
   @{test_code}@
 
-  @{mpi_finalize}@
+  //@{mpi_finalize}@// One could also templte this
   MPI_Finalize();
   printf("Rank %d finished normally\\n", rank);
   return 0;
@@ -261,6 +261,7 @@ class Invalid_negative_rank_error:
 
         tm.set_description("Invalid Rank: %s" % self.invalid_ranks[self.rank_to_use])
 
+        # include the buffer allocation in the template (all ranks execute it)
         tm.register_instruction_block(correct_params.get_buffer_alloc())
 
         send = MPI_Call_Factory().mpi_send(
@@ -274,8 +275,10 @@ class Invalid_negative_rank_error:
         send.set_has_error()
 
         b = InstructionBlock()
-        b.register_operation(send, 1)
-        b.register_operation(get_matching_recv(send), 0)
+        # only rank 0 execute the send
+        b.register_operation(send, 0)
+        # only rank 1 execute the recv
+        b.register_operation(get_matching_recv(send), 1)
         tm.register_instruction_block(b)
 
         return tm