# Copyright 2020 Huawei Technologies Co., Ltd
#
# 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.
# ============================================================================
"""Loss scale manager abstract class."""
from .._checkparam import Validator as validator
from .._checkparam import Rel
from .. import nn
__all__ = ["LossScaleManager", "FixedLossScaleManager", "DynamicLossScaleManager"]
[docs]class LossScaleManager:
"""Loss scale manager abstract class."""
[docs] def get_loss_scale(self):
"""Get loss scale value."""
[docs] def update_loss_scale(self, overflow):
"""
Update loss scale value.
Args:
overflow (bool): Whether it overflows.
"""
[docs] def get_update_cell(self):
"""Get the loss scaling update logic cell."""
[docs]class FixedLossScaleManager(LossScaleManager):
"""
Fixed loss-scale manager.
Args:
loss_scale (float): Loss scale. Default: 128.0.
drop_overflow_update (bool): whether to do optimizer if there is overflow. Default: True.
Examples:
>>> loss_scale_manager = FixedLossScaleManager()
>>> model = Model(net, loss_scale_manager=loss_scale_manager)
"""
def __init__(self, loss_scale=128.0, drop_overflow_update=True):
if loss_scale < 1:
raise ValueError("loss_scale must be at least 1, "
"but got loss_scale {}".format(loss_scale))
self._loss_scale = loss_scale
self._drop_overflow_update = drop_overflow_update
[docs] def get_loss_scale(self):
"""Get loss scale value."""
return self._loss_scale
[docs] def get_drop_overflow_update(self):
"""Get the flag whether to drop optimizer update when there is overflow happened"""
return self._drop_overflow_update
[docs] def update_loss_scale(self, overflow):
"""
Update loss scale value.
Args:
overflow (bool): Whether it overflows.
"""
[docs] def get_update_cell(self):
"Returns the cell for `TrainOneStepWithLossScaleCell`"
if not self._drop_overflow_update:
return None
return nn.FixedLossScaleUpdateCell(self._loss_scale)
[docs]class DynamicLossScaleManager(LossScaleManager):
"""
Dynamic loss-scale manager.
Args:
init_loss_scale (float): Init loss scale. Default: 2**24.
scale_factor (int): Coefficient of increase and decrease. Default: 2.
scale_window (int): Maximum continuous normal steps when there is no overflow. Default: 2000.
Examples:
>>> loss_scale_manager = DynamicLossScaleManager()
>>> model = Model(net, loss_scale_manager=loss_scale_manager)
"""
def __init__(self,
init_loss_scale=2 ** 24,
scale_factor=2,
scale_window=2000):
if init_loss_scale < 1.0:
raise ValueError("Loss scale value should be > 1")
self.loss_scale = init_loss_scale
validator.check_integer("scale_window", scale_window, 0, Rel.GT, self.__class__.__name__)
self.scale_window = scale_window
if scale_factor <= 0:
raise ValueError("Scale factor should be > 1")
self.scale_factor = scale_factor
self.increase_ratio = scale_factor
self.decrease_ratio = 1 / scale_factor
self.cur_iter = 1
self.last_overflow_iter = 0
self.bad_step_max = 1000
self.bad_step = 0
[docs] def get_loss_scale(self):
"""Get loss scale value."""
return self.loss_scale
[docs] def update_loss_scale(self, overflow):
"""
Update loss scale value.
Args:
overflow: Boolean. Whether it overflows.
"""
if overflow:
self.loss_scale = max(self.loss_scale * self.decrease_ratio, 1)
self.last_overflow_iter = self.cur_iter
self.bad_step += 1
else:
if (self.cur_iter - self.last_overflow_iter) % self.scale_window == 0:
self.loss_scale *= self.increase_ratio
self.bad_step = 0
if self.bad_step > self.bad_step_max:
raise RuntimeError("Dynamic loss scale Continuous overflow ", self.bad_step, " times")
self.cur_iter += 1
[docs] def get_drop_overflow_update(self):
"""Get the flag whether to drop optimizer update when there is overflow happened"""
return True
[docs] def get_update_cell(self):
"Returns the cell for `TrainOneStepWithLossScaleCell`"
return nn.DynamicLossScaleUpdateCell(self.loss_scale, self.scale_factor, self.scale_window)