autogen/flaml/onlineml/trial.py

import numpy as np
import logging
import time
import math
import copy
import collections
from typing import Dict, Optional
from sklearn.metrics import mean_squared_error, mean_absolute_error
from vowpalwabbit import pyvw
from flaml.tune import Trial
logger = logging.getLogger(__name__)


def get_ns_feature_dim_from_vw_example(vw_example) -> dict:
    """Get a dictionary of feature dimensionality for each namespace singleton

    NOTE:
        Assumption: assume the vw_example takes one of the following format
        depending on whether the example includes the feature names

        format 1: 'y |ns1 feature1:feature_value1 feature2:feature_value2 |ns2
                ns2 feature3:feature_value3 feature4:feature_value4'
        format 2: 'y | ns1 feature_value1 feature_value2 |
                ns2 feature_value3 feature_value4'

        The output of both cases are {'ns1': 2, 'ns2': 2}

        For more information about the input formate of vw example, please refer to
        https://github.com/VowpalWabbit/vowpal_wabbit/wiki/Input-format
    """
    ns_feature_dim = {}
    data = vw_example.split('|')
    for i in range(1, len(data)):
        if ':' in data[i]:
            ns_w_feature = data[i].split(' ')
            ns = ns_w_feature[0]
            feature = ns_w_feature[1:]
            feature_dim = len(feature)
        else:
            data_split = data[i].split(' ')
            ns = data_split[0]
            feature_dim = len(data_split) - 1
            if len(data_split[-1]) == 0:
                feature_dim -= 1
        ns_feature_dim[ns] = feature_dim
    logger.debug('name space feature dimension %s', ns_feature_dim)
    return ns_feature_dim


class OnlineResult:
    """Class for managing the result statistics of a trial

    Attributes:
        observation_count: the total number of observations
        resource_used: the sum of loss

    Methods:
        update_result(new_loss, new_resource_used, data_dimension)
            Update result
        get_score(score_name)
            Get the score according to the input score_name
    """
    prob_delta = 0.1
    LOSS_MIN = 0.0
    LOSS_MAX = np.inf
    CB_COEF = 0.05  # 0.001 for mse

    def __init__(self, result_type_name: str, cb_coef: Optional[float] = None,
                 init_loss: Optional[float] = 0.0, init_cb: Optional[float] = 100.0,
                 mode: Optional[str] = 'min', sliding_window_size: Optional[int] = 100):
        """
        Args:
            result_type_name (str): The name of the result type
        """
        self._result_type_name = result_type_name  # for example 'mse' or 'mae'
        self._mode = mode
        self._init_loss = init_loss
        # statistics needed for alg
        self.observation_count = 0
        self.resource_used = 0.0
        self._loss_avg = 0.0
        self._loss_cb = init_cb  # a large number (TODO: this can be changed)
        self._cb_coef = cb_coef if cb_coef is not None else self.CB_COEF
        # optional statistics
        self._sliding_window_size = sliding_window_size
        self._loss_queue = collections.deque(maxlen=self._sliding_window_size)

    def update_result(self, new_loss, new_resource_used, data_dimension,
                      bound_of_range=1.0, new_observation_count=1.0):
        """Update result statistics
        """
        self.resource_used += new_resource_used
        # keep the running average instead of sum of loss to avoid over overflow
        self._loss_avg = self._loss_avg * (self.observation_count / (self.observation_count + new_observation_count)
                                           ) + new_loss / (self.observation_count + new_observation_count)
        self.observation_count += new_observation_count
        self._loss_cb = self._update_loss_cb(bound_of_range, data_dimension)
        self._loss_queue.append(new_loss)

    def _update_loss_cb(self, bound_of_range, data_dim,
                        bound_name='sample_complexity_bound'):
        """Calculate bound coef
        """
        if bound_name == 'sample_complexity_bound':
            # set the coefficient in the loss bound
            if 'mae' in self.result_type_name:
                coef = self._cb_coef * bound_of_range
            else:
                coef = 0.001 * bound_of_range

            comp_F = math.sqrt(data_dim)
            n = self.observation_count
            return coef * comp_F * math.sqrt((np.log10(n / OnlineResult.prob_delta)) / n)
        else:
            raise NotImplementedError

    @property
    def result_type_name(self):
        return self._result_type_name

    @property
    def loss_avg(self):
        return self._loss_avg if \
            self.observation_count != 0 else self._init_loss

    @property
    def loss_cb(self):
        return self._loss_cb

    @property
    def loss_lcb(self):
        return max(self._loss_avg - self._loss_cb, OnlineResult.LOSS_MIN)

    @property
    def loss_ucb(self):
        return min(self._loss_avg + self._loss_cb, OnlineResult.LOSS_MAX)

    @property
    def loss_avg_recent(self):
        return sum(self._loss_queue) / len(self._loss_queue) \
            if len(self._loss_queue) != 0 else self._init_loss

    def get_score(self, score_name, cb_ratio=1):
        if 'lcb' in score_name:
            return max(self._loss_avg - cb_ratio * self._loss_cb, OnlineResult.LOSS_MIN)
        elif 'ucb' in score_name:
            return min(self._loss_avg + cb_ratio * self._loss_cb, OnlineResult.LOSS_MAX)
        elif 'avg' in score_name:
            return self._loss_avg
        else:
            raise NotImplementedError


class BaseOnlineTrial(Trial):
    """Class for online trial.

    Attributes：
        config: the config for this trial
        trial_id: the trial_id of this trial
        min_resource_lease (float): the minimum resource realse
        status: the status of this trial
        start_time: the start time of this trial
        custom_trial_name: a custom name for this trial

    Methods:
        set_resource_lease(resource)
        set_status(status)
        set_checked_under_current_champion(checked_under_current_champion)
    """

    def __init__(self,
                 config: dict,
                 min_resource_lease: float,
                 is_champion: Optional[bool] = False,
                 is_checked_under_current_champion: Optional[bool] = True,
                 custom_trial_name: Optional[str] = 'mae',
                 trial_id: Optional[str] = None,
                 ):
        """
        Args:
            config: the config dict
            min_resource_lease: the minimum resource realse
            is_champion: a bool variable
            is_checked_under_current_champion: a bool variable
            custom_trial_name: custom trial name
            trial_id: the trial id
        """
        # ****basic variables
        self.config = config
        self.trial_id = trial_id
        self.status = Trial.PENDING
        self.start_time = time.time()
        self.custom_trial_name = custom_trial_name

        # ***resource budget related variable
        self._min_resource_lease = min_resource_lease
        self._resource_lease = copy.copy(self._min_resource_lease)
        # ***champion related variables
        self._is_champion = is_champion
        # self._is_checked_under_current_champion_ is supposed to be always 1 when the trial is first created
        self._is_checked_under_current_champion = is_checked_under_current_champion

    @property
    def is_champion(self):
        return self._is_champion

    @property
    def is_checked_under_current_champion(self):
        return self._is_checked_under_current_champion

    @property
    def resource_lease(self):
        return self._resource_lease

    def set_checked_under_current_champion(self, checked_under_current_champion: bool):
        """TODO: add documentation why this is needed. This is needed because sometimes
        we want to know whether a trial has been paused since a new champion is promoted.
        We want to try to pause those running trials (even though they are not yet achieve
        the next scheduling check point according to resource used and resource lease),
        because a better trial is likely to be in the new challengers generated by the new
        champion, so we want to try them as soon as possible.
        If we wait until we reach the next scheduling point, we may waste a lot of resource
        (depending on what is the current resource lease) on the old trials (note that new
        trials is not possible to be scheduled to run until there is a slot openning).
        Intuitively speaking, we want to squize an opening slot as soon as possible once
        a new champion is promoted, such that we are able to try newly generated challengers.
        """
        self._is_checked_under_current_champion = checked_under_current_champion

    def set_resource_lease(self, resource: float):
        self._resource_lease = resource

    def set_status(self, status):
        """Sets the status of the trial and record the start time
        """
        self.status = status
        if status == Trial.RUNNING:
            if self.start_time is None:
                self.start_time = time.time()


class VowpalWabbitTrial(BaseOnlineTrial):
    """Implement BaseOnlineTrial for Vowpal Wabbit

    Attributes:
        model: the online model
        result: the anytime result for the online model
        trainable_class: the model class (set as pyvw.vw for VowpalWabbitTrial)

        config: the config for this trial
        trial_id: the trial_id of this trial
        min_resource_lease (float): the minimum resource realse
        status: the status of this trial
        start_time: the start time of this trial
        custom_trial_name: a custom name for this trial

    Methods:
        set_resource_lease(resource)
        set_status(status)
        set_checked_under_current_champion(checked_under_current_champion)

    NOTE:
        About result:
        1. training related results (need to be updated in the trainable class)
        2. result about resources lease (need to be updated externally)

        About namespaces in vw:
        - Wiki in vw:
        https://github.com/VowpalWabbit/vowpal_wabbit/wiki/Namespaces
        - Namespace vs features:
        https://stackoverflow.com/questions/28586225/in-vowpal-wabbit-what-is-the-difference-between-a-namespace-and-feature
    """
    MODEL_CLASS = pyvw.vw
    cost_unit = 1.0
    interactions_config_key = 'interactions'
    MIN_RES_CONST = 5

    def __init__(self,
                 config: dict,
                 min_resource_lease: float,
                 metric: str = 'mae',
                 is_champion: Optional[bool] = False,
                 is_checked_under_current_champion: Optional[bool] = True,
                 custom_trial_name: Optional[str] = 'vw_mae_clipped',
                 trial_id: Optional[str] = None,
                 cb_coef: Optional[float] = None,
                 ):
        """Constructor

        Args:
            config (dict): the config of the trial (note that the config is a set
                because the hyperparameters are )
            min_resource_lease (float): the minimum resource lease
            metric (str): the loss metric
            is_champion (bool): indicates whether the trial is the current champion or not
            is_checked_under_current_champion (bool): indicates whether this trials has
                been paused under the current champion
            trial_id (str): id of the trial (if None, it will be generated in the constructor)

        """
        # attributes
        self.trial_id = self._config_to_id(config) if trial_id is None else trial_id
        logger.info('Create trial with trial_id: %s', self.trial_id)
        super().__init__(config, min_resource_lease, is_champion, is_checked_under_current_champion,
                         custom_trial_name, self.trial_id)
        self.model = None   # model is None until the config is scheduled to run
        self.result = None
        self.trainable_class = self.MODEL_CLASS
        # variables that are needed during online training
        self._metric = metric
        self._y_min_observed = None
        self._y_max_observed = None
        # application dependent variables
        self._dim = None
        self._cb_coef = cb_coef

    @staticmethod
    def _config_to_id(config):
        """Generate an id for the provided config
        """
        # sort config keys
        sorted_k_list = sorted(list(config.keys()))
        config_id_full = ''
        for key in sorted_k_list:
            v = config[key]
            config_id = '|'
            if isinstance(v, set):
                value_list = sorted(v)
                config_id += '_'.join([str(k) for k in value_list])
            else:
                config_id += str(v)
            config_id_full = config_id_full + config_id
        return config_id_full

    def _initialize_vw_model(self, vw_example):
        """Initialize a vw model using the trainable_class
        """
        self._vw_config = self.config.copy()
        ns_interactions = self.config.get(VowpalWabbitTrial.interactions_config_key, None)
        # ensure the feature interaction config is a list (required by VW)
        if ns_interactions is not None:
            self._vw_config[VowpalWabbitTrial.interactions_config_key] \
                = list(ns_interactions)
        # get the dimensionality of the feature according to the namespace configuration
        namespace_feature_dim = get_ns_feature_dim_from_vw_example(vw_example)
        self._dim = self._get_dim_from_ns(namespace_feature_dim, ns_interactions)
        # construct an instance of vw model using the input config and fixed config
        self.model = self.trainable_class(**self._vw_config)
        self.result = OnlineResult(self._metric,
                                   cb_coef=self._cb_coef,
                                   init_loss=0.0, init_cb=100.0,)

    def train_eval_model_online(self, data_sample, y_pred):
        """Train and eval model online
        """
        # extract info needed the first time we see the data
        if self._resource_lease == 'auto' or self._resource_lease is None:
            assert self._dim is not None
            self._resource_lease = self._dim * self.MIN_RES_CONST
        y = self._get_y_from_vw_example(data_sample)
        self._update_y_range(y)
        if self.model is None:
            # initialize self.model and self.result
            self._initialize_vw_model(data_sample)
        # do one step of learning
        self.model.learn(data_sample)
        # update training related results accordingly
        new_loss = self._get_loss(y, y_pred, self._metric,
                                  self._y_min_observed, self._y_max_observed)
        # udpate sample size, sum of loss, and cost
        data_sample_size = 1
        bound_of_range = self._y_max_observed - self._y_min_observed
        if bound_of_range == 0:
            bound_of_range = 1.0
        self.result.update_result(new_loss,
                                  VowpalWabbitTrial.cost_unit * data_sample_size,
                                  self._dim, bound_of_range)

    def predict(self, x):
        """Predict using the model
        """
        if self.model is None:
            # initialize self.model and self.result
            self._initialize_vw_model(x)
        return self.model.predict(x)

    def _get_loss(self, y_true, y_pred, loss_func_name, y_min_observed, y_max_observed):
        """Get instantaneous loss from y_true and y_pred, and loss_func_name
            For mae_clip, we clip y_pred in the observed range of y
        """
        if 'mse' in loss_func_name or 'squared' in loss_func_name:
            loss_func = mean_squared_error
        elif 'mae' in loss_func_name or 'absolute' in loss_func_name:
            loss_func = mean_absolute_error
            if y_min_observed is not None and y_max_observed is not None and \
               'clip' in loss_func_name:
                # clip y_pred in the observed range of y
                y_pred = min(y_max_observed, max(y_pred, y_min_observed))
        else:
            raise NotImplementedError
        return loss_func([y_true], [y_pred])

    def _update_y_range(self, y):
        """Maintain running observed minimum and maximum target value
        """
        if self._y_min_observed is None or y < self._y_min_observed:
            self._y_min_observed = y
        if self._y_max_observed is None or y > self._y_max_observed:
            self._y_max_observed = y

    @staticmethod
    def _get_dim_from_ns(namespace_feature_dim: dict, namespace_interactions: [set, list]):
        """Get the dimensionality of the corresponding feature of input namespace set
        """
        total_dim = sum(namespace_feature_dim.values())
        if namespace_interactions:
            for f in namespace_interactions:
                ns_dim = 1.0
                for c in f:
                    ns_dim *= namespace_feature_dim[c]
                total_dim += ns_dim
        return total_dim

    def clean_up_model(self):
        self.model = None
        self.result = None

    @staticmethod
    def _get_y_from_vw_example(vw_example):
        """Get y from a vw_example. this works for regression datasets.
        """
        return float(vw_example.split('|')[0])