stable/freqtrade/optimize/hyperopt.py

# pragma pylint: disable=too-many-instance-attributes, pointless-string-statement

"""
This module contains the hyperopt logic
"""

import io
import locale
import logging
import random
import warnings
from collections import OrderedDict
from datetime import datetime
from math import ceil
from operator import itemgetter
from pathlib import Path
from pprint import pformat
from typing import Any, Dict, List, Optional

import progressbar
import rapidjson
import tabulate
from colorama import Fore, Style
from colorama import init as colorama_init
from joblib import Parallel, cpu_count, delayed, dump, load, wrap_non_picklable_objects
from pandas import DataFrame, isna, json_normalize

from freqtrade.constants import DATETIME_PRINT_FORMAT, LAST_BT_RESULT_FN
from freqtrade.data.converter import trim_dataframe
from freqtrade.data.history import get_timerange
from freqtrade.exceptions import OperationalException
from freqtrade.misc import file_dump_json, plural, round_dict
from freqtrade.optimize.backtesting import Backtesting
# Import IHyperOpt and IHyperOptLoss to allow unpickling classes from these modules
from freqtrade.optimize.hyperopt_interface import IHyperOpt  # noqa: F401
from freqtrade.optimize.hyperopt_loss_interface import IHyperOptLoss  # noqa: F401
from freqtrade.resolvers.hyperopt_resolver import HyperOptLossResolver, HyperOptResolver
from freqtrade.strategy import IStrategy


# Suppress scikit-learn FutureWarnings from skopt
with warnings.catch_warnings():
    warnings.filterwarnings("ignore", category=FutureWarning)
    from skopt import Optimizer
    from skopt.space import Dimension

progressbar.streams.wrap_stderr()
progressbar.streams.wrap_stdout()
logger = logging.getLogger(__name__)


INITIAL_POINTS = 30

# Keep no more than SKOPT_MODEL_QUEUE_SIZE models
# in the skopt model queue, to optimize memory consumption
SKOPT_MODEL_QUEUE_SIZE = 10

MAX_LOSS = 100000  # just a big enough number to be bad result in loss optimization


class Hyperopt:
    """
    Hyperopt class, this class contains all the logic to run a hyperopt simulation

    To run a backtest:
    hyperopt = Hyperopt(config)
    hyperopt.start()
    """

    def __init__(self, config: Dict[str, Any]) -> None:
        self.config = config

        self.backtesting = Backtesting(self.config)

        self.custom_hyperopt = HyperOptResolver.load_hyperopt(self.config)

        self.custom_hyperoptloss = HyperOptLossResolver.load_hyperoptloss(self.config)
        self.calculate_loss = self.custom_hyperoptloss.hyperopt_loss_function
        time_now = datetime.now().strftime("%Y-%m-%d_%H-%M-%S")
        self.results_file = (self.config['user_data_dir'] /
                             'hyperopt_results' / f'hyperopt_results_{time_now}.pickle')
        self.data_pickle_file = (self.config['user_data_dir'] /
                                 'hyperopt_results' / 'hyperopt_tickerdata.pkl')
        self.total_epochs = config.get('epochs', 0)

        self.current_best_loss = 100

        self.clean_hyperopt()

        self.num_epochs_saved = 0

        # Previous evaluations
        self.epochs: List = []

        # Populate functions here (hasattr is slow so should not be run during "regular" operations)
        if hasattr(self.custom_hyperopt, 'populate_indicators'):
            self.backtesting.strategy.advise_indicators = (  # type: ignore
                self.custom_hyperopt.populate_indicators)  # type: ignore
        if hasattr(self.custom_hyperopt, 'populate_buy_trend'):
            self.backtesting.strategy.advise_buy = (  # type: ignore
                self.custom_hyperopt.populate_buy_trend)  # type: ignore
        if hasattr(self.custom_hyperopt, 'populate_sell_trend'):
            self.backtesting.strategy.advise_sell = (  # type: ignore
                self.custom_hyperopt.populate_sell_trend)  # type: ignore

        # Use max_open_trades for hyperopt as well, except --disable-max-market-positions is set
        if self.config.get('use_max_market_positions', True):
            self.max_open_trades = self.config['max_open_trades']
        else:
            logger.debug('Ignoring max_open_trades (--disable-max-market-positions was used) ...')
            self.max_open_trades = 0
        self.position_stacking = self.config.get('position_stacking', False)

        if self.has_space('sell'):
            # Make sure use_sell_signal is enabled
            if 'ask_strategy' not in self.config:
                self.config['ask_strategy'] = {}
            self.config['ask_strategy']['use_sell_signal'] = True

        self.print_all = self.config.get('print_all', False)
        self.hyperopt_table_header = 0
        self.print_colorized = self.config.get('print_colorized', False)
        self.print_json = self.config.get('print_json', False)

    @staticmethod
    def get_lock_filename(config: Dict[str, Any]) -> str:

        return str(config['user_data_dir'] / 'hyperopt.lock')

    def clean_hyperopt(self) -> None:
        """
        Remove hyperopt pickle files to restart hyperopt.
        """
        for f in [self.data_pickle_file, self.results_file]:
            p = Path(f)
            if p.is_file():
                logger.info(f"Removing `{p}`.")
                p.unlink()

    def _get_params_dict(self, raw_params: List[Any]) -> Dict:

        dimensions: List[Dimension] = self.dimensions

        # Ensure the number of dimensions match
        # the number of parameters in the list.
        if len(raw_params) != len(dimensions):
            raise ValueError('Mismatch in number of search-space dimensions.')

        # Return a dict where the keys are the names of the dimensions
        # and the values are taken from the list of parameters.
        return {d.name: v for d, v in zip(dimensions, raw_params)}

    def _save_results(self) -> None:
        """
        Save hyperopt results to file
        """
        num_epochs = len(self.epochs)
        if num_epochs > self.num_epochs_saved:
            logger.debug(f"Saving {num_epochs} {plural(num_epochs, 'epoch')}.")
            dump(self.epochs, self.results_file)
            self.num_epochs_saved = num_epochs
            logger.debug(f"{self.num_epochs_saved} {plural(self.num_epochs_saved, 'epoch')} "
                         f"saved to '{self.results_file}'.")
            # Store hyperopt filename
            latest_filename = Path.joinpath(self.results_file.parent, LAST_BT_RESULT_FN)
            file_dump_json(latest_filename, {'latest_hyperopt': str(self.results_file.name)},
                           log=False)

    @staticmethod
    def _read_results(results_file: Path) -> List:
        """
        Read hyperopt results from file
        """
        logger.info("Reading epochs from '%s'", results_file)
        data = load(results_file)
        return data

    def _get_params_details(self, params: Dict) -> Dict:
        """
        Return the params for each space
        """
        result: Dict = {}

        if self.has_space('buy'):
            result['buy'] = {p.name: params.get(p.name)
                             for p in self.hyperopt_space('buy')}
        if self.has_space('sell'):
            result['sell'] = {p.name: params.get(p.name)
                              for p in self.hyperopt_space('sell')}
        if self.has_space('roi'):
            result['roi'] = self.custom_hyperopt.generate_roi_table(params)
        if self.has_space('stoploss'):
            result['stoploss'] = {p.name: params.get(p.name)
                                  for p in self.hyperopt_space('stoploss')}
        if self.has_space('trailing'):
            result['trailing'] = self.custom_hyperopt.generate_trailing_params(params)

        return result

    @staticmethod
    def print_epoch_details(results, total_epochs: int, print_json: bool,
                            no_header: bool = False, header_str: str = None) -> None:
        """
        Display details of the hyperopt result
        """
        params = results.get('params_details', {})

        # Default header string
        if header_str is None:
            header_str = "Best result"

        if not no_header:
            explanation_str = Hyperopt._format_explanation_string(results, total_epochs)
            print(f"\n{header_str}:\n\n{explanation_str}\n")

        if print_json:
            result_dict: Dict = {}
            for s in ['buy', 'sell', 'roi', 'stoploss', 'trailing']:
                Hyperopt._params_update_for_json(result_dict, params, s)
            print(rapidjson.dumps(result_dict, default=str, number_mode=rapidjson.NM_NATIVE))

        else:
            Hyperopt._params_pretty_print(params, 'buy', "Buy hyperspace params:")
            Hyperopt._params_pretty_print(params, 'sell', "Sell hyperspace params:")
            Hyperopt._params_pretty_print(params, 'roi', "ROI table:")
            Hyperopt._params_pretty_print(params, 'stoploss', "Stoploss:")
            Hyperopt._params_pretty_print(params, 'trailing', "Trailing stop:")

    @staticmethod
    def _params_update_for_json(result_dict, params, space: str) -> None:
        if space in params:
            space_params = Hyperopt._space_params(params, space)
            if space in ['buy', 'sell']:
                result_dict.setdefault('params', {}).update(space_params)
            elif space == 'roi':
                # TODO: get rid of OrderedDict when support for python 3.6 will be
                # dropped (dicts keep the order as the language feature)

                # Convert keys in min_roi dict to strings because
                # rapidjson cannot dump dicts with integer keys...
                # OrderedDict is used to keep the numeric order of the items
                # in the dict.
                result_dict['minimal_roi'] = OrderedDict(
                    (str(k), v) for k, v in space_params.items()
                )
            else:  # 'stoploss', 'trailing'
                result_dict.update(space_params)

    @staticmethod
    def _params_pretty_print(params, space: str, header: str) -> None:
        if space in params:
            space_params = Hyperopt._space_params(params, space, 5)
            params_result = f"\n# {header}\n"
            if space == 'stoploss':
                params_result += f"stoploss = {space_params.get('stoploss')}"
            elif space == 'roi':
                # TODO: get rid of OrderedDict when support for python 3.6 will be
                # dropped (dicts keep the order as the language feature)
                minimal_roi_result = rapidjson.dumps(
                    OrderedDict(
                        (str(k), v) for k, v in space_params.items()
                    ),
                    default=str, indent=4, number_mode=rapidjson.NM_NATIVE)
                params_result += f"minimal_roi = {minimal_roi_result}"
            elif space == 'trailing':

                for k, v in space_params.items():
                    params_result += f'{k} = {v}\n'

            else:
                params_result += f"{space}_params = {pformat(space_params, indent=4)}"
                params_result = params_result.replace("}", "\n}").replace("{", "{\n ")

            params_result = params_result.replace("\n", "\n    ")
            print(params_result)

    @staticmethod
    def _space_params(params, space: str, r: int = None) -> Dict:
        d = params[space]
        # Round floats to `r` digits after the decimal point if requested
        return round_dict(d, r) if r else d

    @staticmethod
    def is_best_loss(results, current_best_loss: float) -> bool:
        return results['loss'] < current_best_loss

    def print_results(self, results) -> None:
        """
        Log results if it is better than any previous evaluation
        """
        is_best = results['is_best']

        if self.print_all or is_best:
            print(
                self.get_result_table(
                    self.config, results, self.total_epochs,
                    self.print_all, self.print_colorized,
                    self.hyperopt_table_header
                )
            )
            self.hyperopt_table_header = 2

    @staticmethod
    def _format_explanation_string(results, total_epochs) -> str:
        return (("*" if results['is_initial_point'] else " ") +
                f"{results['current_epoch']:5d}/{total_epochs}: " +
                f"{results['results_explanation']} " +
                f"Objective: {results['loss']:.5f}")

    @staticmethod
    def get_result_table(config: dict, results: list, total_epochs: int, highlight_best: bool,
                         print_colorized: bool, remove_header: int) -> str:
        """
        Log result table
        """
        if not results:
            return ''

        tabulate.PRESERVE_WHITESPACE = True

        trials = json_normalize(results, max_level=1)
        trials['Best'] = ''
        if 'results_metrics.winsdrawslosses' not in trials.columns:
            # Ensure compatibility with older versions of hyperopt results
            trials['results_metrics.winsdrawslosses'] = 'N/A'

        trials = trials[['Best', 'current_epoch', 'results_metrics.trade_count',
                         'results_metrics.winsdrawslosses',
                         'results_metrics.avg_profit', 'results_metrics.total_profit',
                         'results_metrics.profit', 'results_metrics.duration',
                         'loss', 'is_initial_point', 'is_best']]
        trials.columns = ['Best', 'Epoch', 'Trades', ' Win Draw Loss', 'Avg profit',
                          'Total profit', 'Profit', 'Avg duration', 'Objective',
                          'is_initial_point', 'is_best']
        trials['is_profit'] = False
        trials.loc[trials['is_initial_point'], 'Best'] = '*     '
        trials.loc[trials['is_best'], 'Best'] = 'Best'
        trials.loc[trials['is_initial_point'] & trials['is_best'], 'Best'] = '* Best'
        trials.loc[trials['Total profit'] > 0, 'is_profit'] = True
        trials['Trades'] = trials['Trades'].astype(str)

        trials['Epoch'] = trials['Epoch'].apply(
            lambda x: '{}/{}'.format(str(x).rjust(len(str(total_epochs)), ' '), total_epochs)
        )
        trials['Avg profit'] = trials['Avg profit'].apply(
            lambda x: '{:,.2f}%'.format(x).rjust(7, ' ') if not isna(x) else "--".rjust(7, ' ')
        )
        trials['Avg duration'] = trials['Avg duration'].apply(
            lambda x: '{:,.1f} m'.format(x).rjust(7, ' ') if not isna(x) else "--".rjust(7, ' ')
        )
        trials['Objective'] = trials['Objective'].apply(
            lambda x: '{:,.5f}'.format(x).rjust(8, ' ') if x != 100000 else "N/A".rjust(8, ' ')
        )

        trials['Profit'] = trials.apply(
            lambda x: '{:,.8f} {} {}'.format(
                x['Total profit'], config['stake_currency'],
                '({:,.2f}%)'.format(x['Profit']).rjust(10, ' ')
            ).rjust(25+len(config['stake_currency']))
            if x['Total profit'] != 0.0 else '--'.rjust(25+len(config['stake_currency'])),
            axis=1
        )
        trials = trials.drop(columns=['Total profit'])

        if print_colorized:
            for i in range(len(trials)):
                if trials.loc[i]['is_profit']:
                    for j in range(len(trials.loc[i])-3):
                        trials.iat[i, j] = "{}{}{}".format(Fore.GREEN,
                                                           str(trials.loc[i][j]), Fore.RESET)
                if trials.loc[i]['is_best'] and highlight_best:
                    for j in range(len(trials.loc[i])-3):
                        trials.iat[i, j] = "{}{}{}".format(Style.BRIGHT,
                                                           str(trials.loc[i][j]), Style.RESET_ALL)

        trials = trials.drop(columns=['is_initial_point', 'is_best', 'is_profit'])
        if remove_header > 0:
            table = tabulate.tabulate(
                trials.to_dict(orient='list'), tablefmt='orgtbl',
                headers='keys', stralign="right"
            )

            table = table.split("\n", remove_header)[remove_header]
        elif remove_header < 0:
            table = tabulate.tabulate(
                trials.to_dict(orient='list'), tablefmt='psql',
                headers='keys', stralign="right"
            )
            table = "\n".join(table.split("\n")[0:remove_header])
        else:
            table = tabulate.tabulate(
                trials.to_dict(orient='list'), tablefmt='psql',
                headers='keys', stralign="right"
            )
        return table

    @staticmethod
    def export_csv_file(config: dict, results: list, total_epochs: int, highlight_best: bool,
                        csv_file: str) -> None:
        """
        Log result to csv-file
        """
        if not results:
            return

        # Verification for overwrite
        if Path(csv_file).is_file():
            logger.error(f"CSV file already exists: {csv_file}")
            return

        try:
            io.open(csv_file, 'w+').close()
        except IOError:
            logger.error(f"Failed to create CSV file: {csv_file}")
            return

        trials = json_normalize(results, max_level=1)
        trials['Best'] = ''
        trials['Stake currency'] = config['stake_currency']

        base_metrics = ['Best', 'current_epoch', 'results_metrics.trade_count',
                        'results_metrics.avg_profit', 'results_metrics.total_profit',
                        'Stake currency', 'results_metrics.profit', 'results_metrics.duration',
                        'loss', 'is_initial_point', 'is_best']
        param_metrics = [("params_dict."+param) for param in results[0]['params_dict'].keys()]
        trials = trials[base_metrics + param_metrics]

        base_columns = ['Best', 'Epoch', 'Trades', 'Avg profit', 'Total profit', 'Stake currency',
                        'Profit', 'Avg duration', 'Objective', 'is_initial_point', 'is_best']
        param_columns = list(results[0]['params_dict'].keys())
        trials.columns = base_columns + param_columns

        trials['is_profit'] = False
        trials.loc[trials['is_initial_point'], 'Best'] = '*'
        trials.loc[trials['is_best'], 'Best'] = 'Best'
        trials.loc[trials['is_initial_point'] & trials['is_best'], 'Best'] = '* Best'
        trials.loc[trials['Total profit'] > 0, 'is_profit'] = True
        trials['Epoch'] = trials['Epoch'].astype(str)
        trials['Trades'] = trials['Trades'].astype(str)

        trials['Total profit'] = trials['Total profit'].apply(
            lambda x: '{:,.8f}'.format(x) if x != 0.0 else ""
        )
        trials['Profit'] = trials['Profit'].apply(
            lambda x: '{:,.2f}'.format(x) if not isna(x) else ""
        )
        trials['Avg profit'] = trials['Avg profit'].apply(
            lambda x: '{:,.2f}%'.format(x) if not isna(x) else ""
        )
        trials['Avg duration'] = trials['Avg duration'].apply(
            lambda x: '{:,.1f} m'.format(x) if not isna(x) else ""
        )
        trials['Objective'] = trials['Objective'].apply(
            lambda x: '{:,.5f}'.format(x) if x != 100000 else ""
        )

        trials = trials.drop(columns=['is_initial_point', 'is_best', 'is_profit'])
        trials.to_csv(csv_file, index=False, header=True, mode='w', encoding='UTF-8')
        logger.info(f"CSV file created: {csv_file}")

    def has_space(self, space: str) -> bool:
        """
        Tell if the space value is contained in the configuration
        """
        # The 'trailing' space is not included in the 'default' set of spaces
        if space == 'trailing':
            return any(s in self.config['spaces'] for s in [space, 'all'])
        else:
            return any(s in self.config['spaces'] for s in [space, 'all', 'default'])

    def hyperopt_space(self, space: Optional[str] = None) -> List[Dimension]:
        """
        Return the dimensions in the hyperoptimization space.
        :param space: Defines hyperspace to return dimensions for.
        If None, then the self.has_space() will be used to return dimensions
        for all hyperspaces used.
        """
        spaces: List[Dimension] = []

        if space == 'buy' or (space is None and self.has_space('buy')):
            logger.debug("Hyperopt has 'buy' space")
            spaces += self.custom_hyperopt.indicator_space()

        if space == 'sell' or (space is None and self.has_space('sell')):
            logger.debug("Hyperopt has 'sell' space")
            spaces += self.custom_hyperopt.sell_indicator_space()

        if space == 'roi' or (space is None and self.has_space('roi')):
            logger.debug("Hyperopt has 'roi' space")
            spaces += self.custom_hyperopt.roi_space()

        if space == 'stoploss' or (space is None and self.has_space('stoploss')):
            logger.debug("Hyperopt has 'stoploss' space")
            spaces += self.custom_hyperopt.stoploss_space()

        if space == 'trailing' or (space is None and self.has_space('trailing')):
            logger.debug("Hyperopt has 'trailing' space")
            spaces += self.custom_hyperopt.trailing_space()

        return spaces

    def generate_optimizer(self, raw_params: List[Any], iteration=None) -> Dict:
        """
        Used Optimize function. Called once per epoch to optimize whatever is configured.
        Keep this function as optimized as possible!
        """
        params_dict = self._get_params_dict(raw_params)
        params_details = self._get_params_details(params_dict)

        if self.has_space('roi'):
            self.backtesting.strategy.minimal_roi = (  # type: ignore
                self.custom_hyperopt.generate_roi_table(params_dict))

        if self.has_space('buy'):
            self.backtesting.strategy.advise_buy = (  # type: ignore
                self.custom_hyperopt.buy_strategy_generator(params_dict))

        if self.has_space('sell'):
            self.backtesting.strategy.advise_sell = (  # type: ignore
                self.custom_hyperopt.sell_strategy_generator(params_dict))

        if self.has_space('stoploss'):
            self.backtesting.strategy.stoploss = params_dict['stoploss']

        if self.has_space('trailing'):
            d = self.custom_hyperopt.generate_trailing_params(params_dict)
            self.backtesting.strategy.trailing_stop = d['trailing_stop']
            self.backtesting.strategy.trailing_stop_positive = d['trailing_stop_positive']
            self.backtesting.strategy.trailing_stop_positive_offset = \
                d['trailing_stop_positive_offset']
            self.backtesting.strategy.trailing_only_offset_is_reached = \
                d['trailing_only_offset_is_reached']

        processed = load(self.data_pickle_file)

        min_date, max_date = get_timerange(processed)

        backtesting_results = self.backtesting.backtest(
            processed=processed,
            start_date=min_date.datetime,
            end_date=max_date.datetime,
            max_open_trades=self.max_open_trades,
            position_stacking=self.position_stacking,
            enable_protections=self.config.get('enable_protections', False),

        )
        return self._get_results_dict(backtesting_results, min_date, max_date,
                                      params_dict, params_details,
                                      processed=processed)

    def _get_results_dict(self, backtesting_results, min_date, max_date,
                          params_dict, params_details, processed: Dict[str, DataFrame]):
        results_metrics = self._calculate_results_metrics(backtesting_results)
        results_explanation = self._format_results_explanation_string(results_metrics)

        trade_count = results_metrics['trade_count']
        total_profit = results_metrics['total_profit']

        # If this evaluation contains too short amount of trades to be
        # interesting -- consider it as 'bad' (assigned max. loss value)
        # in order to cast this hyperspace point away from optimization
        # path. We do not want to optimize 'hodl' strategies.
        loss: float = MAX_LOSS
        if trade_count >= self.config['hyperopt_min_trades']:
            loss = self.calculate_loss(results=backtesting_results, trade_count=trade_count,
                                       min_date=min_date.datetime, max_date=max_date.datetime,
                                       config=self.config, processed=processed)
        return {
            'loss': loss,
            'params_dict': params_dict,
            'params_details': params_details,
            'results_metrics': results_metrics,
            'results_explanation': results_explanation,
            'total_profit': total_profit,
        }

    def _calculate_results_metrics(self, backtesting_results: DataFrame) -> Dict:
        wins = len(backtesting_results[backtesting_results['profit_ratio'] > 0])
        draws = len(backtesting_results[backtesting_results['profit_ratio'] == 0])
        losses = len(backtesting_results[backtesting_results['profit_ratio'] < 0])
        return {
            'trade_count': len(backtesting_results.index),
            'wins': wins,
            'draws': draws,
            'losses': losses,
            'winsdrawslosses': f"{wins:>4} {draws:>4} {losses:>4}",
            'avg_profit': backtesting_results['profit_ratio'].mean() * 100.0,
            'median_profit': backtesting_results['profit_ratio'].median() * 100.0,
            'total_profit': backtesting_results['profit_abs'].sum(),
            'profit': backtesting_results['profit_ratio'].sum() * 100.0,
            'duration': backtesting_results['trade_duration'].mean(),
        }

    def _format_results_explanation_string(self, results_metrics: Dict) -> str:
        """
        Return the formatted results explanation in a string
        """
        stake_cur = self.config['stake_currency']
        return (f"{results_metrics['trade_count']:6d} trades. "
                f"{results_metrics['wins']}/{results_metrics['draws']}"
                f"/{results_metrics['losses']} Wins/Draws/Losses. "
                f"Avg profit {results_metrics['avg_profit']: 6.2f}%. "
                f"Median profit {results_metrics['median_profit']: 6.2f}%. "
                f"Total profit {results_metrics['total_profit']: 11.8f} {stake_cur} "
                f"({results_metrics['profit']: 7.2f}\N{GREEK CAPITAL LETTER SIGMA}%). "
                f"Avg duration {results_metrics['duration']:5.1f} min."
                ).encode(locale.getpreferredencoding(), 'replace').decode('utf-8')

    def get_optimizer(self, dimensions: List[Dimension], cpu_count) -> Optimizer:
        return Optimizer(
            dimensions,
            base_estimator="ET",
            acq_optimizer="auto",
            n_initial_points=INITIAL_POINTS,
            acq_optimizer_kwargs={'n_jobs': cpu_count},
            random_state=self.random_state,
            model_queue_size=SKOPT_MODEL_QUEUE_SIZE,
        )

    def run_optimizer_parallel(self, parallel, asked, i) -> List:
        return parallel(delayed(
                        wrap_non_picklable_objects(self.generate_optimizer))(v, i) for v in asked)

    @staticmethod
    def load_previous_results(results_file: Path) -> List:
        """
        Load data for epochs from the file if we have one
        """
        epochs: List = []
        if results_file.is_file() and results_file.stat().st_size > 0:
            epochs = Hyperopt._read_results(results_file)
            # Detection of some old format, without 'is_best' field saved
            if epochs[0].get('is_best') is None:
                raise OperationalException(
                    "The file with Hyperopt results is incompatible with this version "
                    "of Freqtrade and cannot be loaded.")
            logger.info(f"Loaded {len(epochs)} previous evaluations from disk.")
        return epochs

    def _set_random_state(self, random_state: Optional[int]) -> int:
        return random_state or random.randint(1, 2**16 - 1)

    def start(self) -> None:
        self.random_state = self._set_random_state(self.config.get('hyperopt_random_state', None))
        logger.info(f"Using optimizer random state: {self.random_state}")
        self.hyperopt_table_header = -1
        data, timerange = self.backtesting.load_bt_data()

        preprocessed = self.backtesting.strategy.ohlcvdata_to_dataframe(data)

        # Trim startup period from analyzed dataframe
        for pair, df in preprocessed.items():
            preprocessed[pair] = trim_dataframe(df, timerange)
        min_date, max_date = get_timerange(preprocessed)

        logger.info(f'Hyperopting with data from {min_date.strftime(DATETIME_PRINT_FORMAT)} '
                    f'up to {max_date.strftime(DATETIME_PRINT_FORMAT)} '
                    f'({(max_date - min_date).days} days)..')

        dump(preprocessed, self.data_pickle_file)

        # We don't need exchange instance anymore while running hyperopt
        self.backtesting.exchange.close()
        self.backtesting.exchange._api = None  # type: ignore
        self.backtesting.exchange._api_async = None  # type: ignore
        # self.backtesting.exchange = None  # type: ignore
        self.backtesting.pairlists = None  # type: ignore
        self.backtesting.strategy.dp = None  # type: ignore
        IStrategy.dp = None  # type: ignore

        cpus = cpu_count()
        logger.info(f"Found {cpus} CPU cores. Let's make them scream!")
        config_jobs = self.config.get('hyperopt_jobs', -1)
        logger.info(f'Number of parallel jobs set as: {config_jobs}')

        self.dimensions: List[Dimension] = self.hyperopt_space()
        self.opt = self.get_optimizer(self.dimensions, config_jobs)

        if self.print_colorized:
            colorama_init(autoreset=True)

        try:
            with Parallel(n_jobs=config_jobs) as parallel:
                jobs = parallel._effective_n_jobs()
                logger.info(f'Effective number of parallel workers used: {jobs}')

                # Define progressbar
                if self.print_colorized:
                    widgets = [
                        ' [Epoch ', progressbar.Counter(), ' of ', str(self.total_epochs),
                        ' (', progressbar.Percentage(), ')] ',
                        progressbar.Bar(marker=progressbar.AnimatedMarker(
                            fill='\N{FULL BLOCK}',
                            fill_wrap=Fore.GREEN + '{}' + Fore.RESET,
                            marker_wrap=Style.BRIGHT + '{}' + Style.RESET_ALL,
                        )),
                        ' [', progressbar.ETA(), ', ', progressbar.Timer(), ']',
                    ]
                else:
                    widgets = [
                        ' [Epoch ', progressbar.Counter(), ' of ', str(self.total_epochs),
                        ' (', progressbar.Percentage(), ')] ',
                        progressbar.Bar(marker=progressbar.AnimatedMarker(
                            fill='\N{FULL BLOCK}',
                        )),
                        ' [', progressbar.ETA(), ', ', progressbar.Timer(), ']',
                    ]
                with progressbar.ProgressBar(
                         max_value=self.total_epochs, redirect_stdout=False, redirect_stderr=False,
                         widgets=widgets
                     ) as pbar:
                    EVALS = ceil(self.total_epochs / jobs)
                    for i in range(EVALS):
                        # Correct the number of epochs to be processed for the last
                        # iteration (should not exceed self.total_epochs in total)
                        n_rest = (i + 1) * jobs - self.total_epochs
                        current_jobs = jobs - n_rest if n_rest > 0 else jobs

                        asked = self.opt.ask(n_points=current_jobs)
                        f_val = self.run_optimizer_parallel(parallel, asked, i)
                        self.opt.tell(asked, [v['loss'] for v in f_val])

                        # Calculate progressbar outputs
                        for j, val in enumerate(f_val):
                            # Use human-friendly indexes here (starting from 1)
                            current = i * jobs + j + 1
                            val['current_epoch'] = current
                            val['is_initial_point'] = current <= INITIAL_POINTS

                            logger.debug(f"Optimizer epoch evaluated: {val}")

                            is_best = self.is_best_loss(val, self.current_best_loss)
                            # This value is assigned here and not in the optimization method
                            # to keep proper order in the list of results. That's because
                            # evaluations can take different time. Here they are aligned in the
                            # order they will be shown to the user.
                            val['is_best'] = is_best
                            self.print_results(val)

                            if is_best:
                                self.current_best_loss = val['loss']
                            self.epochs.append(val)

                            # Save results after each best epoch and every 100 epochs
                            if is_best or current % 100 == 0:
                                self._save_results()

                            pbar.update(current)

        except KeyboardInterrupt:
            print('User interrupted..')

        self._save_results()
        logger.info(f"{self.num_epochs_saved} {plural(self.num_epochs_saved, 'epoch')} "
                    f"saved to '{self.results_file}'.")

        if self.epochs:
            sorted_epochs = sorted(self.epochs, key=itemgetter('loss'))
            best_epoch = sorted_epochs[0]
            self.print_epoch_details(best_epoch, self.total_epochs, self.print_json)
        else:
            # This is printed when Ctrl+C is pressed quickly, before first epochs have
            # a chance to be evaluated.
            print("No epochs evaluated yet, no best result.")