!!----------------------------------------------------------------------
   !!                   ***  vectopt_loop_substitute  ***
   !!----------------------------------------------------------------------
   !! ** purpose :   substitute the inner loop starting and inding indices 
   !!      to allow unrolling of do-loop using CPP macro.
   !!----------------------------------------------------------------------
#if defined key_vectopt_loop
#  define fs_2     1
#  define fs_jpim1 jpi
#else
#  define fs_2     2
#  define fs_jpim1 jpim1
#endif