TFSlim - 加载VGG16的已保存检查点时出现问题

Question

(1)我试图通过将预训练的权重加载到除该fc8层之外的所有层中来使用TFSlim来微调VGG-16网络.我通过使用TF-SLIm函数实现了这一点,如下所示:

import tensorflow as tf
import tensorflow.contrib.slim as slim
import tensorflow.contrib.slim.nets as nets

vgg = nets.vgg

# Specify where the Model, trained on ImageNet, was saved.
model_path = 'path/to/vgg_16.ckpt'

# Specify where the new model will live:
log_dir = 'path/to/log/'

images = tf.placeholder(tf.float32, [None, 224, 224, 3])
predictions = vgg.vgg_16(images)

variables_to_restore = slim.get_variables_to_restore(exclude=['fc8'])
restorer = tf.train.Saver(variables_to_restore)




init = tf.initialize_all_variables()

with tf.Session() as sess:
   sess.run(init)
   restorer.restore(sess,model_path)
   print "model restored"

只要我不更改num_classesVGG16型号,这样就可以正常工作.我想做的是将num_classes1000从200 更改为200.我的印象是,如果我通过定义一个vgg16-modified替换fc8产生200个输出的新类来进行此修改,(以及variables_to_restore = slim.get_variables_to_restore(exclude=['fc8']) 一切都会很好和花花公子但是,tensorflow抱怨尺寸不匹配:

InvalidArgumentError (see above for traceback): Assign requires shapes of both tensors to match. lhs shape= [1,1,4096,200] rhs shape= [1,1,4096,1000] 

那么,一个人如何真正去做呢？TFSlim的文档非常不完整,Github上散布了多个版本 - 因此没有得到太多帮助.

Answer 1

您可以尝试使用slim的恢复方式 - slim.assign_from_checkpoint.

苗条来源中有相关文档:https: //github.com/tensorflow/tensorflow/blob/129665119ea60640f7ed921f36db9b5c23455224/tensorflow/contrib/slim/python/slim/learning.py

对应部分:

*************************************************
* Fine-Tuning Part of a model from a checkpoint *
*************************************************
Rather than initializing all of the weights of a given model, we sometimes
only want to restore some of the weights from a checkpoint. To do this, one
need only filter those variables to initialize as follows:
  ...
  # Create the train_op
  train_op = slim.learning.create_train_op(total_loss, optimizer)
  checkpoint_path = '/path/to/old_model_checkpoint'
  # Specify the variables to restore via a list of inclusion or exclusion
  # patterns:
  variables_to_restore = slim.get_variables_to_restore(
      include=["conv"], exclude=["fc8", "fc9])
  # or
  variables_to_restore = slim.get_variables_to_restore(exclude=["conv"])
  init_assign_op, init_feed_dict = slim.assign_from_checkpoint(
      checkpoint_path, variables_to_restore)
  # Create an initial assignment function.
  def InitAssignFn(sess):
      sess.run(init_assign_op, init_feed_dict)
  # Run training.
  slim.learning.train(train_op, my_log_dir, init_fn=InitAssignFn)

更新

我尝试了以下方法:

import tensorflow as tf
import tensorflow.contrib.slim as slim
import tensorflow.contrib.slim.nets as nets
images = tf.placeholder(tf.float32, [None, 224, 224, 3])
predictions = nets.vgg.vgg_16(images)
print [v.name for v in slim.get_variables_to_restore(exclude=['fc8']) ]

得到这个输出(缩短):

[u'vgg_16/conv1/conv1_1/weights:0',
 u'vgg_16/conv1/conv1_1/biases:0',
 …
 u'vgg_16/fc6/weights:0',
 u'vgg_16/fc6/biases:0',
 u'vgg_16/fc7/weights:0',
 u'vgg_16/fc7/biases:0',
 u'vgg_16/fc8/weights:0',
 u'vgg_16/fc8/biases:0']

所以看起来你应该在范围前加上vgg_16:

print [v.name for v in slim.get_variables_to_restore(exclude=['vgg_16/fc8']) ]

给(缩短):

[u'vgg_16/conv1/conv1_1/weights:0',
 u'vgg_16/conv1/conv1_1/biases:0',
 …
 u'vgg_16/fc6/weights:0',
 u'vgg_16/fc6/biases:0',
 u'vgg_16/fc7/weights:0',
 u'vgg_16/fc7/biases:0']

更新2

完整的示例,无错误地执行(在我的系统中).

import tensorflow as tf
import tensorflow.contrib.slim as slim
import tensorflow.contrib.slim.nets as nets

s = tf.Session(config=tf.ConfigProto(gpu_options={'allow_growth':True}))

images = tf.placeholder(tf.float32, [None, 224, 224, 3])
predictions = nets.vgg.vgg_16(images, 200)
variables_to_restore = slim.get_variables_to_restore(exclude=['vgg_16/fc8'])
init_assign_op, init_feed_dict = slim.assign_from_checkpoint('./vgg16.ckpt', variables_to_restore)
s.run(init_assign_op, init_feed_dict)

在上面的示例中,为1000个类VGG16模型vgg16.ckpt保存了一个检查点tf.train.Saver.

使用此检查点以及200个类模型(包括fc8)的所有变量会产生以下错误:

init_assign_op, init_feed_dict = slim.assign_from_checkpoint('./vgg16.ckpt', slim.get_variables_to_restore())
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
      1 init_assign_op, init_feed_dict = slim.assign_from_checkpoint(
----> 2       './vgg16.ckpt', slim.get_variables_to_restore())

/usr/local/lib/python2.7/dist-packages/tensorflow/contrib/framework/python/ops/variables.pyc in assign_from_checkpoint(model_path, var_list)
    527     assign_ops.append(var.assign(placeholder_value))
    528
--> 529     feed_dict[placeholder_value] = var_value.reshape(var.get_shape())
    530
    531   assign_op = control_flow_ops.group(*assign_ops)

ValueError: total size of new array must be unchanged