为什么 tf.GradientTape() 在手动观察模型变量时使用较少的 GPU 内存?

问题描述

因此,当我使用 tf.GradientTape() 自动监控 resnet 模型中的可训练变量时,计算机抛出了内存不足错误代码如下:

x_mini = preprocess_input(x_train)  
with tf.GradientTape() as tape:    
    outputs = model(x_mini,training=True)

但是,如果我禁用自动监视器并手动观察可训练变量,我可以输入更大的数据而不会出现任何内存问题。代码如下:

x_mini = preprocess_input(x_train)
with tf.GradientTape(watch_accessed_variables=False) as tape:
    tape.watch(model.trainable_variables)
    outputs = model(x_mini,training=True)

我想知道我手动操作时磁带是否遗漏了一些变量。

以下是可运行代码(如果您评论选项 1,则会显示内存不足错误):我使用 Tesla T4 15G GPU 和 tensorflow 2.3

import tensorflow as tf
import numpy as np
from keras.models import Model
import keras.layers as ly
x_train = tf.convert_to_tensor(np.random.randint(0,255,(900,224,3)),dtype=tf.dtypes.float32)
y_train = tf.convert_to_tensor([0,1,0],dtype=tf.dtypes.float32)
print(x_train.shape)

tf.keras.backend.clear_session()
resnet_model = tf.keras.applications.resnet.resnet50(weights='imagenet',include_top=False,input_shape=(224,3))
resnet_model.trainable = False
inputs = tf.keras.Input(shape=(224,3))
x = resnet_model(inputs,training=False)
x = ly.GlobalAveragePooling2D()(x)
x = ly.Dropout(0.2)(x)
outputs = ly.Dense(3,activation='softmax')(x)
model = Model(inputs,outputs)
mcross = tf.keras.losses.categorical_crossentropy
macc = tf.keras.metrics.categorical_accuracy
base_learning_rate = 0.0001
optimizer = tf.keras.optimizers.Adam(base_learning_rate)

def cross_entropy(y_true,y_pred):
    y_pred = y_pred / tf.reduce_sum(y_pred,True)
    y_pred = tf.clip_by_value(y_pred,1e-3,1-1e-3)
    return -tf.reduce_sum(y_true*tf.math.log(y_pred),1)

# option 1
# manually tapping variables 
with tf.GradientTape(watch_accessed_variables=False) as tape:
    tape.watch(model.trainable_variables)
    y_pred = model(x_train,training=True)
    loss = cross_entropy(y_train,tf.reduce_mean(y_pred,keepdims=True))
gradients = tape.gradient(loss,model.trainable_variables)

#option 2
# automatically tapping variable
with tf.GradientTape() as tape:
    y_pred = model(x_train,model.trainable_variables)

还有错误信息:

--------------------------------------------------------------------------- ResourceExhaustedError                    Traceback (most recent call last) <ipython-input-4-42e45caeae41> in <module>
     31 # automatically tapping variable
     32 with tf.GradientTape() as tape:
---> 33     y_pred = model(x_train,training=True)
     34     loss = cross_entropy(y_train,keepdims=True))
     35 gradients = tape.gradient(loss,model.trainable_variables)

/opt/conda/lib/python3.7/site-packages/tensorflow/python/keras/engine/base_layer.py in __call__(self,*args,**kwargs)
    983 
    984         with ops.enable_auto_cast_variables(self._compute_dtype_object):
--> 985           outputs = call_fn(inputs,**kwargs)
    986 
    987         if self._activity_regularizer:

/opt/conda/lib/python3.7/site-packages/tensorflow/python/keras/engine/functional.py in call(self,inputs,training,mask)
    384     """
    385     return self._run_internal_graph(
--> 386         inputs,training=training,mask=mask)
    387 
    388   def compute_output_shape(self,input_shape):

/opt/conda/lib/python3.7/site-packages/tensorflow/python/keras/engine/functional.py in _run_internal_graph(self,mask)
    506 
    507         args,kwargs = node.map_arguments(tensor_dict)
--> 508         outputs = node.layer(*args,**kwargs)
    509 
    510         # Update tensor_dict.

/opt/conda/lib/python3.7/site-packages/tensorflow/python/keras/engine/base_layer.py in __call__(self,**kwargs)
    986 
    987         if self._activity_regularizer:

/opt/conda/lib/python3.7/site-packages/tensorflow/python/keras/layers/convolutional.py in call(self,inputs)
    245       inputs = array_ops.pad(inputs,self._compute_causal_padding(inputs))
    246 
--> 247     outputs = self._convolution_op(inputs,self.kernel)
    248 
    249     if self.use_bias:

/opt/conda/lib/python3.7/site-packages/tensorflow/python/util/dispatch.py in wrapper(*args,**kwargs)
    199     """Call target,and fall back on dispatchers if there is a TypeError."""
    200     try:
--> 201       return target(*args,**kwargs)
    202     except (TypeError,ValueError):
    203       # Note: convert_to_eager_tensor currently raises a ValueError,not a

/opt/conda/lib/python3.7/site-packages/tensorflow/python/ops/nn_ops.py in convolution_v2(input,filters,strides,padding,data_format,dilations,name)    1016       data_format=data_format,1017       dilations=dilations,-> 1018       name=name)    1019     1020 

/opt/conda/lib/python3.7/site-packages/tensorflow/python/ops/nn_ops.py in convolution_internal(input,name,call_from_convolution,num_spatial_dims)    1146      data_format=data_format,1147           dilations=dilations,-> 1148           name=name)    1149     else:    1150       if channel_index == 1:

/opt/conda/lib/python3.7/site-packages/tensorflow/python/ops/nn_ops.py in _conv2d_expanded_batch(input,name)    2590         data_format=data_format,2591         dilations=dilations,-> 2592         name=name)    2593   return squeeze_batch_dims(    2594       input,/opt/conda/lib/python3.7/site-packages/tensorflow/python/ops/gen_nn_ops.py in conv2d(input,filter,use_cudnn_on_gpu,explicit_paddings,name)
    936       return _result
    937     except _core._NotOkStatusException as e:
--> 938       _ops.raise_from_not_ok_status(e,name)
    939     except _core._FallbackException:
    940       pass

/opt/conda/lib/python3.7/site-packages/tensorflow/python/framework/ops.py in raise_from_not_ok_status(e,name)    6841   message = e.message + (" name: " + name if name is not None else "")    6842   # pylint: disable=protected-access
-> 6843   six.raise_from(core._status_to_exception(e.code,message),None)    6844   # pylint: enable=protected-access    6845

/opt/conda/lib/python3.7/site-packages/six.py in raise_from(value,from_value)

ResourceExhaustedError: OOM when allocating tensor with shape[900,56,256] and type float on /job:localhost/replica:0/task:0/device:GPU:0 by allocator GPU_0_bfc [Op:Conv2D]

解决方法

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