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accum_optimizers.py
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accum_optimizers.py
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import tensorflow as tf
from tensorflow.python.keras.optimizer_v2.optimizer_v2 import OptimizerV2
from tensorflow.python import ops, math_ops, state_ops, control_flow_ops
from tensorflow.keras.optimizers import Optimizer
import tensorflow.keras.backend as K
__all__ = ['AdamAccumulated']
class AdamAccumulated(OptimizerV2):
"""Optimizer that implements the Adam algorithm with gradient accumulation."""
def __init__(self,
accumulation_steps,
learning_rate=0.001,
beta_1=0.9,
beta_2=0.999,
epsilon=1e-7,
amsgrad=False,
name='Adam',
**kwargs):
r"""Construct a new Adam optimizer.
Args:
accumulation_steps: An integer. Update gradient in every accumulation steps.
learning_rate: A Tensor or a floating point value. The learning rate.
beta_1: A float value or a constant float tensor. The exponential decay
rate for the 1st moment estimates.
beta_2: A float value or a constant float tensor. The exponential decay
rate for the 2nd moment estimates.
epsilon: A small constant for numerical stability. This epsilon is
"epsilon hat" in the Kingma and Ba paper (in the formula just before
Section 2.1), not the epsilon in Algorithm 1 of the paper.
amsgrad: boolean. Whether to apply AMSGrad variant of this algorithm from
the paper "On the Convergence of Adam and beyond".
name: Optional name for the operations created when applying gradients.
Defaults to "Adam". @compatibility(eager) When eager execution is
enabled, `learning_rate`, `beta_1`, `beta_2`, and `epsilon` can each be
a callable that takes no arguments and returns the actual value to use.
This can be useful for changing these values across different
invocations of optimizer functions. @end_compatibility
**kwargs: keyword arguments. Allowed to be {`clipnorm`, `clipvalue`, `lr`,
`decay`}. `clipnorm` is clip gradients by norm; `clipvalue` is clip
gradients by value, `decay` is included for backward compatibility to
allow time inverse decay of learning rate. `lr` is included for backward
compatibility, recommended to use `learning_rate` instead.
"""
super(AdamAccumulated, self).__init__(name, **kwargs)
self._set_hyper('accumulation_steps', accumulation_steps)
self._set_hyper('learning_rate', kwargs.get('lr', learning_rate))
self._set_hyper('decay', self._initial_decay)
self._set_hyper('beta_1', beta_1)
self._set_hyper('beta_2', beta_2)
self.epsilon = epsilon # or backend_config.epsilon()
self.amsgrad = amsgrad
def _create_slots(self, var_list):
for var in var_list:
self.add_slot(var, 'g')
for var in var_list:
self.add_slot(var, 'm')
for var in var_list:
self.add_slot(var, 'v')
if self.amsgrad:
for var in var_list:
self.add_slot(var, 'vhat')
def set_weights(self, weights):
params = self.weights
num_vars = int((len(params) - 1) / 2)
if len(weights) == 3 * num_vars + 1:
weights = weights[:len(params)]
super(AdamAccumulated, self).set_weights(weights)
def _resource_apply_dense(self, grad, var):
var_dtype = var.dtype.base_dtype
lr_t = self._decayed_lr(var_dtype)
beta_1_t = self._get_hyper('beta_1', var_dtype)
beta_2_t = self._get_hyper('beta_2', var_dtype)
accumulation_steps = self._get_hyper('accumulation_steps', 'int64')
update_cond = tf.equal((self.iterations + 1) % accumulation_steps, 0)
sub_step = self.iterations % accumulation_steps + 1
local_step = math_ops.cast(self.iterations // accumulation_steps + 1, var_dtype)
beta_1_power = math_ops.pow(beta_1_t, local_step)
beta_2_power = math_ops.pow(beta_2_t, local_step)
epsilon_t = ops.convert_to_tensor(self.epsilon, var_dtype)
lr = (lr_t * math_ops.sqrt(1 - beta_2_power) / (1 - beta_1_power))
lr = tf.where(update_cond, lr, 0.0)
g = self.get_slot(var, 'g')
g_a = grad / math_ops.cast(accumulation_steps, var_dtype)
g_t = tf.where(tf.equal(sub_step, 1),
g_a,
g + (g_a - g) / math_ops.cast(sub_step, var_dtype))
g_t = state_ops.assign(g, g_t, use_locking=self._use_locking)
m = self.get_slot(var, 'm')
m_t = tf.where(update_cond, m * beta_1_t + g_t * (1 - beta_1_t), m)
m_t = state_ops.assign(m, m_t, use_locking=self._use_locking)
v = self.get_slot(var, 'v')
v_t = tf.where(update_cond, v * beta_2_t + (g_t * g_t) * (1 - beta_2_t), v)
v_t = state_ops.assign(v, v_t, use_locking=self._use_locking)
if not self.amsgrad:
v_sqrt = math_ops.sqrt(v_t)
var_update = state_ops.assign_sub(
var, lr * m_t / (v_sqrt + epsilon_t), use_locking=self._use_locking)
return control_flow_ops.group(*[var_update, m_t, v_t])
else:
v_hat = self.get_slot(var, 'vhat')
v_hat_t = tf.where(update_cond, math_ops.maximum(v_hat, v_t), v_hat)
with ops.control_dependencies([v_hat_t]):
v_hat_t = state_ops.assign(
v_hat, v_hat_t, use_locking=self._use_locking)
v_hat_sqrt = math_ops.sqrt(v_hat_t)
var_update = state_ops.assign_sub(
var,
lr * m_t / (v_hat_sqrt + epsilon_t),
use_locking=self._use_locking)
return control_flow_ops.group(*[var_update, m_t, v_t, v_hat_t])
def get_config(self):
config = super(AdamAccumulated, self).get_config()
config.update({
'accumulation_steps': self._serialize_hyperparameter('accumulation_steps'),
'learning_rate': self._serialize_hyperparameter('learning_rate'),
'decay': self._serialize_hyperparameter('decay'),
'beta_1': self._serialize_hyperparameter('beta_1'),
'beta_2': self._serialize_hyperparameter('beta_2'),
'epsilon': self.epsilon,
'amsgrad': self.amsgrad,
})
return config
class AccumOptimizer(Optimizer):
"""Optimizer
Inheriting Optimizer class, wrapping the original optimizer
to achieve a new corresponding optimizer of gradient accumulation.
# Arguments
optimizer: an instance of keras optimizer (supporting
all keras optimizers currently available);
steps_per_update: the steps of gradient accumulation
# Returns
a new keras optimizer.
"""
def __init__(self, optimizer, steps_per_update=1, **kwargs):
super(AccumOptimizer, self).__init__(**kwargs)
self.optimizer = optimizer
with K.name_scope(self.__class__.__name__):
self.steps_per_update = steps_per_update
self.iterations = K.variable(0, dtype='int64', name='iterations')
self.cond = K.equal(self.iterations % self.steps_per_update, 0)
self.lr = self.optimizer.lr
self.optimizer.lr = K.switch(self.cond, self.optimizer.lr, 0.)
for attr in ['momentum', 'rho', 'beta_1', 'beta_2']:
if hasattr(self.optimizer, attr):
value = getattr(self.optimizer, attr)
setattr(self, attr, value)
setattr(self.optimizer, attr, K.switch(self.cond, value, 1 - 1e-7))
for attr in self.optimizer.get_config():
if not hasattr(self, attr):
value = getattr(self.optimizer, attr)
setattr(self, attr, value)
# Cover the original get_gradients method with accumulative gradients.
def get_gradients(loss, params):
return [ag / self.steps_per_update for ag in self.accum_grads]
self.optimizer.get_gradients = get_gradients
def get_updates(self, loss, params):
self.updates = [
K.update_add(self.iterations, 1),
K.update_add(self.optimizer.iterations, K.cast(self.cond, 'int64')),
]
# gradient accumulation
self.accum_grads = [K.zeros(K.int_shape(p), dtype=K.dtype(p)) for p in params]
grads = self.get_gradients(loss, params)
for g, ag in zip(grads, self.accum_grads):
self.updates.append(K.update(ag, K.switch(self.cond, g, ag + g)))
# inheriting updates of original optimizer
self.updates.extend(self.optimizer.get_updates(loss, params)[1:])
self.weights.extend(self.optimizer.weights)
return self.updates
def get_config(self):
iterations = K.eval(self.iterations)
K.set_value(self.iterations, 0)
config = self.optimizer.get_config()
K.set_value(self.iterations, iterations)
return config