# Copyright (c) Microsoft Corporation.
# Licensed under the MIT license.
import logging
import datetime
from nni.assessor import Assessor, AssessResult
from nni.utils import extract_scalar_history
from .model_factory import CurveModel
logger = logging.getLogger('curvefitting_Assessor')
[docs]class CurvefittingAssessor(Assessor):
"""CurvefittingAssessor uses learning curve fitting algorithm to predict the learning curve performance in the future.
It stops a pending trial X at step S if the trial's forecast result at target step is convergence and lower than the
best performance in the history.
Parameters
----------
epoch_num : int
The total number of epoch
optimize_mode : str
optimize mode, 'maximize' or 'minimize'
start_step : int
only after receiving start_step number of reported intermediate results
threshold : float
The threshold that we decide to early stop the worse performance curve.
"""
def __init__(self, epoch_num=20, optimize_mode='maximize', start_step=6, threshold=0.95, gap=1):
if start_step <= 0:
logger.warning('It\'s recommended to set start_step to a positive number')
# Record the target position we predict
self.target_pos = epoch_num
# Record the optimize_mode
if optimize_mode == 'maximize':
self.higher_better = True
elif optimize_mode == 'minimize':
self.higher_better = False
else:
self.higher_better = True
logger.warning('unrecognized optimize_mode %s', optimize_mode)
# Start forecasting when historical data reaches start step
self.start_step = start_step
# Record the compared threshold
self.threshold = threshold
# Record the number of gap
self.gap = gap
# Record the number of intermediate result in the lastest judgment
self.last_judgment_num = dict()
# Record the best performance
self.set_best_performance = False
self.completed_best_performance = None
self.trial_history = []
logger.info('Successfully initials the curvefitting assessor')
[docs] def trial_end(self, trial_job_id, success):
"""update the best performance of completed trial job
Parameters
----------
trial_job_id : int
trial job id
success : bool
True if succssfully finish the experiment, False otherwise
"""
if success:
if self.set_best_performance:
self.completed_best_performance = max(self.completed_best_performance, self.trial_history[-1])
else:
self.set_best_performance = True
self.completed_best_performance = self.trial_history[-1]
logger.info('Updated complted best performance, trial job id: %s', trial_job_id)
else:
logger.info('No need to update, trial job id: %s', trial_job_id)
[docs] def assess_trial(self, trial_job_id, trial_history):
"""assess whether a trial should be early stop by curve fitting algorithm
Parameters
----------
trial_job_id : int
trial job id
trial_history : list
The history performance matrix of each trial
Returns
-------
bool
AssessResult.Good or AssessResult.Bad
Raises
------
Exception
unrecognize exception in curvefitting_assessor
"""
scalar_trial_history = extract_scalar_history(trial_history)
self.trial_history = scalar_trial_history
if not self.set_best_performance:
return AssessResult.Good
curr_step = len(scalar_trial_history)
if curr_step < self.start_step:
return AssessResult.Good
if trial_job_id in self.last_judgment_num.keys() and curr_step - self.last_judgment_num[trial_job_id] < self.gap:
return AssessResult.Good
self.last_judgment_num[trial_job_id] = curr_step
try:
start_time = datetime.datetime.now()
# Predict the final result
curvemodel = CurveModel(self.target_pos)
predict_y = curvemodel.predict(scalar_trial_history)
logger.info('Prediction done. Trial job id = %s. Predict value = %s', trial_job_id, predict_y)
if predict_y is None:
logger.info('wait for more information to predict precisely')
return AssessResult.Good
standard_performance = self.completed_best_performance * self.threshold
end_time = datetime.datetime.now()
if (end_time - start_time).seconds > 60:
logger.warning(
'Curve Fitting Assessor Runtime Exceeds 60s, Trial Id = %s Trial History = %s',
trial_job_id, self.trial_history
)
if self.higher_better:
if predict_y > standard_performance:
return AssessResult.Good
return AssessResult.Bad
else:
if predict_y < standard_performance:
return AssessResult.Good
return AssessResult.Bad
except Exception as exception:
logger.exception('unrecognize exception in curvefitting_assessor %s', exception)