def __create_bootstrap(self, main_root):
		bootstrap_dir = os.path.join(main_root, 'bootstrap')
		safe_mkdir(bootstrap_dir)

		bootstrap = self.__config_mgr.bootstrap()
		self.__bootstrap_mgr.create_bootstrap(bootstrap, bootstrap_dir)
def _acc_grads(g_sum, g_w, g):
  """Accumulate gradients in g, weighted by g_w."""
  return [g_sum_i + g_w * g_i for g_sum_i, g_i in zip(g_sum, g)]