sa_controller.py

#   Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserve.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""The controller used to search hyperparameters or neural architecture"""

import copy
import math
import logging
import numpy as np
import json
from .controller import EvolutionaryController
from log_helper import get_logger

__all__ = ["SAController"]

_logger = get_logger(__name__, level=logging.INFO)


class SAController(EvolutionaryController):
    """Simulated annealing controller."""

    def __init__(self,
                 range_table=None,
                 reduce_rate=0.85,
                 init_temperature=1024,
                 max_try_times=None,
                 init_tokens=None,
                 reward=-1,
                 max_reward=-1,
                 iters=0,
                 best_tokens=None,
                 constrain_func=None,
                 checkpoints=None):
        """Initialize.
        Args:
            range_table(list<int>): Range table.
            reduce_rate(float): The decay rate of temperature.
            init_temperature(float): Init temperature.
            max_try_times(int): max try times before get legal tokens.
            init_tokens(list<int>): The initial tokens.
            constrain_func(function): The callback function used to check whether the tokens meet constraint. None means there is no constraint. Default: None.
            checkpoints(str): if checkpoint is None, donnot save checkpoints, else save scene to checkpoints file.
        """
        super(SAController, self).__init__()
        self._range_table = range_table
        assert isinstance(self._range_table, tuple) and (
            len(self._range_table) == 2)
        self._reduce_rate = reduce_rate
        self._init_temperature = init_temperature
        self._max_try_times = max_try_times
        self._reward = reward
        self._tokens = init_tokens
        self._constrain_func = constrain_func
        self._max_reward = max_reward
        self._best_tokens = best_tokens
        self._iter = iters
        self._checkpoints = checkpoints

    def __getstate__(self):
        d = {}
        for key in self.__dict__:
            if key != "_constrain_func":
                d[key] = self.__dict__[key]
        return d

    def update(self, tokens, reward, iter):
        """
        Update the controller according to latest tokens and reward.
        Args:
            tokens(list<int>): The tokens generated in last step.
            reward(float): The reward of tokens.
        """
        iter = int(iter)
        if iter > self._iter:
            self._iter = iter
        temperature = self._init_temperature * self._reduce_rate**self._iter
        if (reward > self._reward) or (np.random.random() <= math.exp(
            (reward - self._reward) / temperature)):
            self._reward = reward
            self._tokens = tokens
        if reward > self._max_reward:
            self._max_reward = reward
            self._best_tokens = tokens
        _logger.info(
            "Controller - iter: {}; best_reward: {}, best tokens: {}, current_reward: {}; current tokens: {}".
            format(self._iter, self._reward, self._tokens, reward, tokens))

        if self._checkpoints != None:
            self._save_checkpoint(self._checkpoints)


    def next_tokens(self, control_token=None):
        """
        Get next tokens.
        """
        if control_token:
            tokens = control_token[:]
        else:
            tokens = self._tokens
        new_tokens = tokens[:]
        index = int(len(self._range_table[0]) * np.random.random())
        new_tokens[index] = np.random.randint(self._range_table[0][index],
                                              self._range_table[1][index])
        _logger.debug("change index[{}] from {} to {}".format(index, tokens[
            index], new_tokens[index]))
        if self._constrain_func is None or self._max_try_times is None:
            return new_tokens
        for _ in range(self._max_try_times):
            if not self._constrain_func(new_tokens):
                index = int(len(self._range_table[0]) * np.random.random())
                new_tokens = tokens[:]
                new_tokens[index] = np.random.randint(
                    self._range_table[0][index],
                    self._range_table[1][index])
            else:
                break
        return new_tokens

    def _save_checkpoint(self, output_file):
        scene = dict()
        for key in self.__dict__():
            if key in ['_checkpoints']:
                continue
            scene[key] = self.__dict__[key]
        f = open(output_file, 'w')
        json.dump(scene)
        f.close()