def _global_var_name(splittable_dimension, mesh_dimension):
    """Name for a global variable.

  Args:
    splittable_dimension: the name of a splittable dimension (string)
    mesh_dimension: the name of a mesh dimension (string)

  Returns:
    A string, the variable name.
  """
    return 'x_({}:{})'.format(splittable_dimension, mesh_dimension)
