make_target (https://arxiv.org/src/1911.08265v1/anc/pseudocode.py)

pseudocode.py

class Game(object):
  """A single episode of interaction with the environment."""

  def __init__(self, action_space_size: int, discount: float):
    self.environment = Environment()  # Game specific environment.
    self.history = []
    self.rewards = []
    self.child_visits = []
    self.root_values = []
    self.action_space_size = action_space_size
    self.discount = discount

  def make_target(self, state_index: int, num_unroll_steps: int, td_steps: int,
                  to_play: Player):
    # The value target is the discounted root value of the search tree N steps
    # into the future, plus the discounted sum of all rewards until then.
    targets = []
    for current_index in range(state_index, state_index + num_unroll_steps + 1):
      bootstrap_index = current_index + td_steps
      if bootstrap_index < len(self.root_values):
        value = self.root_values[bootstrap_index] * self.discount**td_steps
      else:
        value = 0

      for i, reward in enumerate(self.rewards[current_index:bootstrap_index]):
        value += reward * self.discount**i  # pytype: disable=unsupported-operands

      if current_index < len(self.root_values):
        targets.append((value, self.rewards[current_index],
                        self.child_visits[current_index]))
      else:
        # States past the end of games are treated as absorbing states.
        targets.append((0, 0, []))
    return targets
  
  ...