mirror of
https://github.com/google-deepmind/deepmind-research.git
synced 2026-05-09 21:07:49 +08:00
Victoria Krakovna
683 lines
25 KiB
Python
683 lines
25 KiB
Python
# Copyright 2019 DeepMind Technologies Limited.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ============================================================================
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"""Side Effects Penalties.
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Abstract class for implementing a side effects (impact measure) penalty,
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and various concrete penalties deriving from it.
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"""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import print_function
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import abc
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import collections
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import copy
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import enum
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import random
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import numpy as np
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import six
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from six.moves import range
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from six.moves import zip
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import sonnet as snt
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import tensorflow.compat.v1 as tf
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class Actions(enum.IntEnum):
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"""Enum for actions the agent can take."""
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UP = 0
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DOWN = 1
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LEFT = 2
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RIGHT = 3
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NOOP = 4
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@six.add_metaclass(abc.ABCMeta)
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class Baseline(object):
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"""Base class for baseline states."""
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def __init__(self, start_timestep, exact=False, env=None,
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timestep_to_state=None):
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"""Create a baseline.
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Args:
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start_timestep: starting state timestep
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exact: whether to use an exact or approximate baseline
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env: a copy of the environment (used to simulate exact baselines)
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timestep_to_state: a function that turns timesteps into states
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"""
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self._exact = exact
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self._env = env
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self._timestep_to_state = timestep_to_state
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self._start_timestep = start_timestep
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self._baseline_state = self._timestep_to_state(self._start_timestep)
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self._inaction_next = collections.defaultdict(
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lambda: collections.defaultdict(lambda: 0))
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@abc.abstractmethod
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def calculate(self):
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"""Update and return the baseline state."""
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def sample(self, state):
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"""Sample the outcome of a noop in `state`."""
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d = self._inaction_next[state]
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counts = np.array(list(d.values()))
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index = np.random.choice(a=len(counts), p=counts/sum(counts))
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return list(d.keys())[index]
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def reset(self):
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"""Signal start of new episode."""
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self._baseline_state = self._timestep_to_state(self._start_timestep)
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if self._exact:
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self._env.reset()
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@abc.abstractproperty
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def rollout_func(self):
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"""Function to compute a rollout chain, or None if n/a."""
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@property
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def baseline_state(self):
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return self._baseline_state
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class StartBaseline(Baseline):
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"""Starting state baseline."""
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def calculate(self, *unused_args):
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return self._baseline_state
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@property
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def rollout_func(self):
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return None
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class InactionBaseline(Baseline):
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"""Inaction baseline: the state resulting from taking no-ops from start."""
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def calculate(self, prev_state, action, current_state):
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if self._exact:
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self._baseline_state = self._timestep_to_state(
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self._env.step(Actions.NOOP))
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else:
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if action == Actions.NOOP:
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self._inaction_next[prev_state][current_state] += 1
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if self._baseline_state in self._inaction_next:
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self._baseline_state = self.sample(self._baseline_state)
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return self._baseline_state
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@property
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def rollout_func(self):
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return None
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class StepwiseBaseline(Baseline):
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"""Stepwise baseline: the state one no-op after the previous state."""
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def __init__(self, start_timestep, exact=False, env=None,
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timestep_to_state=None, use_rollouts=True):
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"""Create a stepwise baseline.
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Args:
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start_timestep: starting state timestep
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exact: whether to use an exact or approximate baseline
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env: a copy of the environment (used to simulate exact baselines)
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timestep_to_state: a function that turns timesteps into states
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use_rollouts: whether to use inaction rollouts
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"""
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super(StepwiseBaseline, self).__init__(
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start_timestep, exact, env, timestep_to_state)
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self._rollouts = use_rollouts
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def calculate(self, prev_state, action, current_state):
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"""Update and return the baseline state.
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Args:
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prev_state: the state in which `action` was taken
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action: the action just taken
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current_state: the state resulting from taking `action`
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Returns:
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the baseline state, for computing the penalty for this transition
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"""
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if self._exact:
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if prev_state in self._inaction_next:
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self._baseline_state = self.sample(prev_state)
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else:
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inaction_env = copy.deepcopy(self._env)
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timestep_inaction = inaction_env.step(Actions.NOOP)
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self._baseline_state = self._timestep_to_state(timestep_inaction)
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self._inaction_next[prev_state][self._baseline_state] += 1
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timestep_action = self._env.step(action)
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assert current_state == self._timestep_to_state(timestep_action)
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else:
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if action == Actions.NOOP:
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self._inaction_next[prev_state][current_state] += 1
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if prev_state in self._inaction_next:
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self._baseline_state = self.sample(prev_state)
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else:
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self._baseline_state = prev_state
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return self._baseline_state
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def _inaction_rollout(self, state):
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"""Compute an (approximate) inaction rollout from a state."""
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chain = []
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st = state
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while st not in chain:
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chain.append(st)
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if st in self._inaction_next:
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st = self.sample(st)
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return chain
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def parallel_inaction_rollouts(self, s1, s2):
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"""Compute (approximate) parallel inaction rollouts from two states."""
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chain = []
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states = (s1, s2)
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while states not in chain:
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chain.append(states)
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s1, s2 = states
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states = (self.sample(s1) if s1 in self._inaction_next else s1,
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self.sample(s2) if s2 in self._inaction_next else s2)
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return chain
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@property
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def rollout_func(self):
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return self._inaction_rollout if self._rollouts else None
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@six.add_metaclass(abc.ABCMeta)
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class DeviationMeasure(object):
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"""Base class for deviation measures."""
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@abc.abstractmethod
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def calculate(self):
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"""Calculate the deviation between two states."""
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@abc.abstractmethod
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def update(self):
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"""Update any models after seeing a state transition."""
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class ReachabilityMixin(object):
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"""Class for computing reachability deviation measure.
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Computes the relative/un- reachability given a dictionary of
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reachability scores for pairs of states.
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Expects _reachability, _discount, and _dev_fun attributes to exist in the
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inheriting class.
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"""
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def calculate(self, current_state, baseline_state, rollout_func=None):
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"""Calculate relative/un- reachability between particular states."""
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# relative reachability case
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if self._dev_fun:
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if rollout_func:
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curr_values = self._rollout_values(rollout_func(current_state))
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base_values = self._rollout_values(rollout_func(baseline_state))
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else:
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curr_values = self._reachability[current_state]
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base_values = self._reachability[baseline_state]
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all_s = set(list(curr_values.keys()) + list(base_values.keys()))
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total = 0
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for s in all_s:
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diff = base_values[s] - curr_values[s]
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total += self._dev_fun(diff)
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d = total / len(all_s)
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# unreachability case
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else:
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assert rollout_func is None
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d = 1 - self._reachability[current_state][baseline_state]
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return d
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def _rollout_values(self, chain):
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"""Compute stepwise rollout values for the relative reachability penalty.
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Args:
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chain: chain of states in an inaction rollout starting with the state for
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which to compute the rollout values
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Returns:
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a dictionary of the form:
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{ s : (1-discount) sum_{k=0}^inf discount^k R_s(S_k) }
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where S_k is the k-th state in the inaction rollout from 'state',
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s is a state, and
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R_s(S_k) is the reachability of s from S_k.
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"""
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rollout_values = collections.defaultdict(lambda: 0)
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coeff = 1
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for st in chain:
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for s, rch in six.iteritems(self._reachability[st]):
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rollout_values[s] += coeff * rch * (1.0 - self._discount)
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coeff *= self._discount
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last_state = chain[-1]
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for s, rch in six.iteritems(self._reachability[last_state]):
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rollout_values[s] += coeff * rch
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return rollout_values
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class Reachability(ReachabilityMixin, DeviationMeasure):
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"""Approximate (relative) (un)reachability deviation measure.
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Unreachability (the default, when `dev_fun=None`) uses the length (say, n)
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of the shortest path (sequence of actions) from the current state to the
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baseline state. The reachability score is value_discount ** n.
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Unreachability is then 1.0 - the reachability score.
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Relative reachability (when `dev_fun` is not `None`) considers instead the
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difference in reachability of all other states from the current state
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versus from the baseline state.
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We approximate reachability by only considering state transitions
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that have been observed. Add transitions using the `update` function.
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"""
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def __init__(self, value_discount=1.0, dev_fun=None, discount=None):
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self._value_discount = value_discount
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self._dev_fun = dev_fun
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self._discount = discount
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self._reachability = collections.defaultdict(
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lambda: collections.defaultdict(lambda: 0))
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def update(self, prev_state, current_state, action=None):
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del action # Unused.
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self._reachability[prev_state][prev_state] = 1
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self._reachability[current_state][current_state] = 1
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if self._reachability[prev_state][current_state] < self._value_discount:
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for s1 in self._reachability.keys():
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if self._reachability[s1][prev_state] > 0:
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for s2 in self._reachability[current_state].keys():
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if self._reachability[current_state][s2] > 0:
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self._reachability[s1][s2] = max(
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self._reachability[s1][s2],
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self._reachability[s1][prev_state] * self._value_discount *
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self._reachability[current_state][s2])
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@property
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def discount(self):
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return self._discount
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class UVFAReachability(ReachabilityMixin, DeviationMeasure):
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"""Approximate relative reachability deviation measure using UVFA.
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We approximate reachability using a neural network only trained on state
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transitions that have been observed. For each (s0, action, s1) transition,
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we update the reachability estimate for (s0, action, s) towards the
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reachability estimate between s1 and s, for each s in a random sample of
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size update_sample_size. In particular, the loss for the neural network
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reachability estimate (NN) is
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sum_s(max_a(NN(s1, a, s)) * value_discount - NN(s0, action, s)),
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where the sum is over all sampled s, the max is taken over all actions a.
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At evaluation time, the reachability difference is calculated with respect
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to a randomly sampled set of states of size calc_sample_size.
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"""
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def __init__(
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self,
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value_discount=0.95,
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dev_fun=None,
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discount=0.95,
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state_size=36, # Sokoban default
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num_actions=5,
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update_sample_size=10,
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calc_sample_size=10,
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hidden_size=50,
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representation_size=5,
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num_layers=1,
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base_loss_coeff=0.1,
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num_stored=100):
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# Create networks to generate state representations. To get a reachability
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# estimate, take the dot product of the origin network output and the goal
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# network output, then pass it through a sigmoid function to constrain it to
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# between 0 and 1.
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output_sizes = [hidden_size] * num_layers + [representation_size]
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self._origin_network = snt.nets.MLP(
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output_sizes=output_sizes,
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activation=tf.nn.relu,
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activate_final=False,
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name='origin_network')
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self._goal_network = snt.nets.MLP(
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output_sizes=output_sizes,
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activation=tf.nn.relu,
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activate_final=False,
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name='goal_network')
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self._value_discount = value_discount
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self._dev_fun = dev_fun
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self._discount = discount
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self._state_size = state_size
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self._num_actions = num_actions
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self._update_sample_size = update_sample_size
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self._calc_sample_size = calc_sample_size
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self._num_stored = num_stored
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self._stored_states = set()
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self._state_0_placeholder = tf.placeholder(tf.float32, shape=(state_size))
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self._state_1_placeholder = tf.placeholder(tf.float32, shape=(state_size))
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self._action_placeholder = tf.placeholder(tf.float32, shape=(num_actions))
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self._update_sample_placeholder = tf.placeholder(
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tf.float32, shape=(update_sample_size, state_size))
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self._calc_sample_placeholder = tf.placeholder(
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tf.float32, shape=(calc_sample_size, state_size))
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# Trained to estimate reachability = value_discount ^ distance.
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self._sample_loss = self._get_state_action_loss(
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self._state_0_placeholder,
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self._state_1_placeholder,
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self._action_placeholder,
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self._update_sample_placeholder)
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# Add additional loss to force observed transitions towards value_discount.
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self._base_reachability = self._get_state_sample_reachability(
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self._state_0_placeholder,
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tf.expand_dims(self._state_1_placeholder, axis=0),
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action=self._action_placeholder)
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self._base_case_loss = tf.keras.losses.MSE(self._value_discount,
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self._base_reachability)
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self._opt = tf.train.AdamOptimizer().minimize(self._sample_loss +
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base_loss_coeff *
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self._base_case_loss)
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current_state_reachability = self._get_state_sample_reachability(
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self._state_0_placeholder, self._calc_sample_placeholder)
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baseline_state_reachability = self._get_state_sample_reachability(
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self._state_1_placeholder, self._calc_sample_placeholder)
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self._reachability_calculation = [
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tf.reshape(baseline_state_reachability, [-1]),
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tf.reshape(current_state_reachability, [-1])
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]
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init = tf.global_variables_initializer()
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self._sess = tf.Session()
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self._sess.run(init)
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def calculate(self, current_state, baseline_state, rollout_func=None):
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"""Compute the reachability penalty between two states."""
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current_state = np.array(current_state).flatten()
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baseline_state = np.array(baseline_state).flatten()
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sample = self._sample_n_states(self._calc_sample_size)
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# Run if there are enough states to draw a correctly-sized sample from.
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if sample:
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base, curr = self._sess.run(
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self._reachability_calculation,
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feed_dict={
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self._state_0_placeholder: current_state,
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self._state_1_placeholder: baseline_state,
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self._calc_sample_placeholder: sample
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})
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return sum(map(self._dev_fun, base - curr)) / self._calc_sample_size
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else:
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return 0
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def _sample_n_states(self, n):
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try:
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return random.sample(self._stored_states, n)
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except ValueError:
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return None
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def update(self, prev_state, current_state, action):
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prev_state = np.array(prev_state).flatten()
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current_state = np.array(current_state).flatten()
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one_hot_action = np.zeros(self._num_actions)
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one_hot_action[action] = 1
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sample = self._sample_n_states(self._update_sample_size)
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if self._num_stored is None or len(self._stored_states) < self._num_stored:
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self._stored_states.add(tuple(prev_state))
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self._stored_states.add(tuple(current_state))
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elif (np.random.random() < 0.01 and
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tuple(current_state) not in self._stored_states):
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self._stored_states.pop()
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self._stored_states.add(tuple(current_state))
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# If there aren't enough states to get a full sample, do nothing.
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if sample:
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self._sess.run([self._opt], feed_dict={
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self._state_0_placeholder: prev_state,
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self._state_1_placeholder: current_state,
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self._action_placeholder: one_hot_action,
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self._update_sample_placeholder: sample
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})
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def _get_state_action_loss(self, prev_state, current_state, action, sample):
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"""Get the loss from differences in state reachability estimates."""
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# Calculate NN(s0, action, s) for all s in sample.
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prev_state_reachability = self._get_state_sample_reachability(
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prev_state, sample, action=action)
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# Calculate max_a(NN(s1, a, s)) for all s in sample and all actions a.
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current_state_reachability = tf.stop_gradient(
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self._get_state_sample_reachability(current_state, sample))
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# Combine to return loss.
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return tf.keras.losses.MSE(
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current_state_reachability * self._value_discount,
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prev_state_reachability)
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def _get_state_sample_reachability(self, state, sample, action=None):
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"""Calculate reachability from a state to each item in a sample."""
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if action is None:
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state_options = self._tile_with_all_actions(state)
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else:
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state_options = tf.expand_dims(tf.concat([state, action], axis=0), axis=0)
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goal_representations = self._goal_network(sample)
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# Reachability of sampled states by taking actions
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reach_result = tf.sigmoid(
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tf.reduce_max(
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tf.matmul(
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goal_representations,
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self._origin_network(state_options),
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transpose_b=True),
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axis=1))
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if action is None:
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# Return 1 if sampled state is already reached (equal to state)
|
|
reach_no_action = tf.cast(tf.reduce_all(tf.equal(sample, state), axis=1),
|
|
dtype=tf.float32)
|
|
reach_result = tf.maximum(reach_result, reach_no_action)
|
|
return reach_result
|
|
|
|
def _tile_with_all_actions(self, state):
|
|
"""Returns tensor with all state/action combinations."""
|
|
state_tiled = tf.tile(tf.expand_dims(state, axis=0), [self._num_actions, 1])
|
|
all_actions_tiled = tf.one_hot(
|
|
tf.range(self._num_actions), depth=self._num_actions)
|
|
return tf.concat([state_tiled, all_actions_tiled], axis=1)
|
|
|
|
|
|
class AttainableUtilityMixin(object):
|
|
"""Class for computing attainable utility measure.
|
|
|
|
Computes attainable utility (averaged over a set of utility functions)
|
|
given value functions for each utility function.
|
|
|
|
Expects _u_values, _discount, _value_discount, and _dev_fun attributes to
|
|
exist in the inheriting class.
|
|
"""
|
|
|
|
def calculate(self, current_state, baseline_state, rollout_func=None):
|
|
if rollout_func:
|
|
current_values = self._rollout_values(rollout_func(current_state))
|
|
baseline_values = self._rollout_values(rollout_func(baseline_state))
|
|
else:
|
|
current_values = [u_val[current_state] for u_val in self._u_values]
|
|
baseline_values = [u_val[baseline_state] for u_val in self._u_values]
|
|
penalties = [self._dev_fun(base_val - cur_val) * (1. - self._value_discount)
|
|
for base_val, cur_val in zip(baseline_values, current_values)]
|
|
return sum(penalties) / len(penalties)
|
|
|
|
def _rollout_values(self, chain):
|
|
"""Compute stepwise rollout values for the attainable utility penalty.
|
|
|
|
Args:
|
|
chain: chain of states in an inaction rollout starting with the state
|
|
for which to compute the rollout values
|
|
|
|
Returns:
|
|
a list containing
|
|
(1-discount) sum_{k=0}^inf discount^k V_u(S_k)
|
|
for each utility function u,
|
|
where S_k is the k-th state in the inaction rollout from 'state'.
|
|
"""
|
|
rollout_values = [0 for _ in self._u_values]
|
|
coeff = 1
|
|
for st in chain:
|
|
rollout_values = [rv + coeff * u_val[st] * (1.0 - self._discount)
|
|
for rv, u_val in zip(rollout_values, self._u_values)]
|
|
coeff *= self._discount
|
|
last_state = chain[-1]
|
|
rollout_values = [rv + coeff * u_val[last_state]
|
|
for rv, u_val in zip(rollout_values, self._u_values)]
|
|
return rollout_values
|
|
|
|
def _set_util_funs(self, util_funs):
|
|
"""Set up this instance's utility functions.
|
|
|
|
Args:
|
|
util_funs: either a number of functions to generate or a list of
|
|
pre-defined utility functions, represented as dictionaries
|
|
over states: util_funs[i][s] = u_i(s), the utility of s
|
|
according to u_i.
|
|
"""
|
|
if isinstance(util_funs, int):
|
|
self._util_funs = [
|
|
collections.defaultdict(float) for _ in range(util_funs)
|
|
]
|
|
else:
|
|
self._util_funs = util_funs
|
|
|
|
def _utility(self, u, state):
|
|
"""Apply a random utility function, generating its value if necessary."""
|
|
if state not in u:
|
|
u[state] = np.random.random()
|
|
return u[state]
|
|
|
|
|
|
class AttainableUtility(AttainableUtilityMixin, DeviationMeasure):
|
|
"""Approximate attainable utility deviation measure."""
|
|
|
|
def __init__(self, value_discount=0.99, dev_fun=np.abs, util_funs=10,
|
|
discount=None):
|
|
assert value_discount < 1.0 # AU does not converge otherwise
|
|
self._value_discount = value_discount
|
|
self._dev_fun = dev_fun
|
|
self._discount = discount
|
|
self._set_util_funs(util_funs)
|
|
# u_values[i][s] = V_{u_i}(s), the (approximate) value of s according to u_i
|
|
self._u_values = [
|
|
collections.defaultdict(float) for _ in range(len(self._util_funs))
|
|
]
|
|
# predecessors[s] = set of states known to lead, by some action, to s
|
|
self._predecessors = collections.defaultdict(set)
|
|
|
|
def update(self, prev_state, current_state, action=None):
|
|
"""Update predecessors and attainable utility estimates."""
|
|
del action # Unused.
|
|
self._predecessors[current_state].add(prev_state)
|
|
seen = set()
|
|
queue = [current_state]
|
|
while queue:
|
|
s_to = queue.pop(0)
|
|
seen.add(s_to)
|
|
for u, u_val in zip(self._util_funs, self._u_values):
|
|
for s_from in self._predecessors[s_to]:
|
|
v = self._utility(u, s_from) + self._value_discount * u_val[s_to]
|
|
if u_val[s_from] < v:
|
|
u_val[s_from] = v
|
|
if s_from not in seen:
|
|
queue.append(s_from)
|
|
|
|
|
|
class NoDeviation(DeviationMeasure):
|
|
"""Dummy deviation measure corresponding to no impact penalty."""
|
|
|
|
def calculate(self, *unused_args):
|
|
return 0
|
|
|
|
def update(self, *unused_args):
|
|
pass
|
|
|
|
|
|
class SideEffectPenalty(object):
|
|
"""Impact penalty."""
|
|
|
|
def __init__(
|
|
self, baseline, dev_measure, beta=1.0, nonterminal_weight=0.01,
|
|
use_inseparable_rollout=False):
|
|
"""Make an object to calculate the impact penalty.
|
|
|
|
Args:
|
|
baseline: object for calculating the baseline state
|
|
dev_measure: object for calculating the deviation between states
|
|
beta: weight (scaling factor) for the impact penalty
|
|
nonterminal_weight: penalty weight on nonterminal states.
|
|
use_inseparable_rollout:
|
|
whether to compute the penalty as the average of deviations over
|
|
parallel inaction rollouts from the current and baseline states (True)
|
|
otherwise just between the current state and baseline state (or by
|
|
whatever rollout value is provided in the baseline) (False)
|
|
"""
|
|
self._baseline = baseline
|
|
self._dev_measure = dev_measure
|
|
self._beta = beta
|
|
self._nonterminal_weight = nonterminal_weight
|
|
self._use_inseparable_rollout = use_inseparable_rollout
|
|
|
|
def calculate(self, prev_state, action, current_state):
|
|
"""Calculate the penalty associated with a transition, and update models."""
|
|
def compute_penalty(current_state, baseline_state):
|
|
"""Compute penalty."""
|
|
if self._use_inseparable_rollout:
|
|
penalty = self._rollout_value(current_state, baseline_state,
|
|
self._dev_measure.discount,
|
|
self._dev_measure.calculate)
|
|
else:
|
|
penalty = self._dev_measure.calculate(current_state, baseline_state,
|
|
self._baseline.rollout_func)
|
|
return self._beta * penalty
|
|
if current_state: # not a terminal state
|
|
self._dev_measure.update(prev_state, current_state, action)
|
|
baseline_state =\
|
|
self._baseline.calculate(prev_state, action, current_state)
|
|
penalty = compute_penalty(current_state, baseline_state)
|
|
return self._nonterminal_weight * penalty
|
|
else: # terminal state
|
|
penalty = compute_penalty(prev_state, self._baseline.baseline_state)
|
|
return penalty
|
|
|
|
def reset(self):
|
|
"""Signal start of new episode."""
|
|
self._baseline.reset()
|
|
|
|
def _rollout_value(self, cur_state, base_state, discount, func):
|
|
"""Compute stepwise rollout value for unreachability."""
|
|
# Returns (1-discount) sum_{k=0}^inf discount^k R(S_{t,t+k}, S'_{t,t+k}),
|
|
# where S_{t,t+k} is k-th state in the inaction rollout from current state,
|
|
# S'_{t,t+k} is k-th state in the inaction rollout from baseline state,
|
|
# and R is the reachability function.
|
|
chain = self._baseline.parallel_inaction_rollouts(cur_state, base_state)
|
|
coeff = 1
|
|
rollout_value = 0
|
|
for states in chain:
|
|
rollout_value += (coeff * func(states[0], states[1]) * (1.0 - discount))
|
|
coeff *= discount
|
|
last_states = chain[-1]
|
|
rollout_value += coeff * func(last_states[0], last_states[1])
|
|
return rollout_value
|
|
|
|
@property
|
|
def beta(self):
|
|
return self._beta
|