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[tune] Implement BOHB (#5382)

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This commit is contained in:
Lisa Dunlap
2019-08-13 12:32:07 -07:00
committed by Richard Liaw
parent 79949fb8a0
commit b7d0733362
12 changed files with 519 additions and 30 deletions
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python/ray/tune/schedulers/hyperband.py
+24 -10
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@@ -8,6 +8,7 @@ import logging
from ray.tune.schedulers.trial_scheduler import FIFOScheduler, TrialScheduler
from ray.tune.trial import Trial
from ray.tune.error import TuneError
logger = logging.getLogger(__name__)
@@ -72,6 +73,8 @@ class HyperBandScheduler(FIFOScheduler):
The scheduler will terminate trials after this time has passed.
Note that this is different from the semantics of `max_t` as
mentioned in the original HyperBand paper.
reduction_factor (float): Same as `eta`. Determines how sharp
the difference is between bracket space-time allocation ratios.
"""
def __init__(self,
@@ -79,7 +82,8 @@ class HyperBandScheduler(FIFOScheduler):
reward_attr=None,
metric="episode_reward_mean",
mode="max",
max_t=81):
max_t=81,
reduction_factor=3):
assert max_t > 0, "Max (time_attr) not valid!"
assert mode in ["min", "max"], "`mode` must be 'min' or 'max'!"
@@ -92,8 +96,9 @@ class HyperBandScheduler(FIFOScheduler):
"Setting `metric={}` and `mode=max`.".format(reward_attr))
FIFOScheduler.__init__(self)
self._eta = 3
self._s_max_1 = 5
self._eta = reduction_factor
self._s_max_1 = int(
np.round(np.log(max_t) / np.log(reduction_factor))) + 1
self._max_t_attr = max_t
# bracket max trials
self._get_n0 = lambda s: int(
@@ -173,10 +178,10 @@ class HyperBandScheduler(FIFOScheduler):
if bracket.continue_trial(trial):
return TrialScheduler.CONTINUE
action = self._process_bracket(trial_runner, bracket, trial)
action = self._process_bracket(trial_runner, bracket)
return action
def _process_bracket(self, trial_runner, bracket, trial):
def _process_bracket(self, trial_runner, bracket):
"""This is called whenever a trial makes progress.
When all live trials in the bracket have no more iterations left,
@@ -202,15 +207,15 @@ class HyperBandScheduler(FIFOScheduler):
bracket.cleanup_trial(t)
action = TrialScheduler.STOP
else:
raise Exception("Trial with unexpected status encountered")
raise TuneError("Trial with unexpected status encountered")
# ready the good trials - if trial is too far ahead, don't continue
for t in good:
if t.status not in [Trial.PAUSED, Trial.RUNNING]:
raise Exception("Trial with unexpected status encountered")
raise TuneError("Trial with unexpected status encountered")
if bracket.continue_trial(t):
if t.status == Trial.PAUSED:
trial_runner.trial_executor.unpause_trial(t)
self._unpause_trial(trial_runner, t)
elif t.status == Trial.RUNNING:
action = TrialScheduler.CONTINUE
return action
@@ -223,7 +228,7 @@ class HyperBandScheduler(FIFOScheduler):
bracket, _ = self._trial_info[trial]
bracket.cleanup_trial(trial)
if not bracket.finished():
self._process_bracket(trial_runner, bracket, trial)
self._process_bracket(trial_runner, bracket)
def on_trial_complete(self, trial_runner, trial, result):
"""Cleans up trial info from bracket if trial completed early."""
@@ -279,6 +284,15 @@ class HyperBandScheduler(FIFOScheduler):
out += "\n {}".format(bracket)
return out
def state(self):
return {
"num_brackets": sum(len(band) for band in self._hyperbands),
"num_stopped": self._num_stopped
}
def _unpause_trial(self, trial_runner, trial):
trial_runner.trial_executor.unpause_trial(trial)
class Bracket():
"""Logical object for tracking Hyperband bracket progress. Keeps track
@@ -349,7 +363,7 @@ class Bracket():
self._r *= self._eta
self._r = int(min(self._r, self._max_t_attr - self._cumul_r))
self._cumul_r += self._r
self._cumul_r = self._r
sorted_trials = sorted(
self._live_trials,
key=lambda t: metric_op * self._live_trials[t][metric])