我无法弄清楚如何在转换为 tf.Estimator
的Keras模型中使用Tensorflow Hub嵌入列( hub.text_embedding_column
) .
如果我不将模型转换为估算器,则可以在Keras模型中使用嵌入 .
例如,一些虚拟数据定义如下:
x_train = ['the quick brown fox', 'jumps over a lazy']
x_eval = ['the quick brown fox', 'jumps over a lazy']
y_train = [0, 1]
y_eval = [0, 1]
然后,我可以使用以下代码来训练keras模型而不会出错
embed = hub.Module('https://tfhub.dev/google/nnlm-en-dim128/1')
def _embed(x):
return embed(tf.squeeze(tf.cast(x, tf.string)))
# workaround for keras
x_train = np.array(x_train, dtype=object)[:, np.newaxis]
x_eval = np.array(x_eval, dtype=object)[:, np.newaxis]
input_text = tf.keras.layers.Input(shape=(1,), dtype=tf.string)
embedding = tf.keras.layers.Lambda(_embed, output_shape=(128,))(input_text)
pred = tf.keras.layers.Dense(1, activation='sigmoid')(dense)
model = tf.keras.Model(inputs=input_text, outputs=pred)
model.compile(loss='binary_crossentropy', optimizer='adam', metrics=['accuracy'])
model.summary()
with tf.Session() as sess:
sess.run([tf.global_variables_initializer(), tf.tables_initializer()])
model.fit(x_train, y_train, epochs=1, validation_data=(x_eval, y_eval))
但是,如果我尝试使用 tf.keras.estimator.model_to_estimator
将其转换为估算器,突然间我再也无法训练模型了 .
embedding = hub.text_embedding_column('text', 'https://tfhub.dev/google/nnlm-en-dim128/1')
features = {'text': x_train}
labels = y_train[:, np.newaxis]
input_fn = tf.estimator.inputs.numpy_input_fn(features, labels, shuffle=False)
embedding_input = tf.keras.layers.Input(shape=(128,), dtype=tf.float32, name='text')
logits = tf.keras.layers.Dense(1, activation='softmax', name='logits')(embedding_input)
model = tf.keras.Model(inputs=embedding_input, outputs=logits)
model.compile(loss='binary_crossentropy', optimizer='adam', metrics=['accuracy'])
model.summary()
estimator = tf.keras.estimator.model_to_estimator(model)
estimator.train(input_fn, max_steps=1)
如果我使用像 tf.estimator.DNNEstimator
这样的预制估算器,我也可以毫无错误地训练模型 .
embedding = hub.text_embedding_column('text', 'https://tfhub.dev/google/nnlm-en-dim128/1')
features = {'text': x_train}
labels = y_train[:, np.newaxis]
input_fn = tf.estimator.inputs.numpy_input_fn(features, labels, shuffle=False)
estimator = tf.estimator.DNNClassifier([32], [embedding])
当我尝试使用转换为估算器的keras模型训练它时得到的错误是:
Input 0 of layer logits is incompatible with the layer: : expected min_ndim=2, found ndim=1. Full shape received: [None]
完整的堆栈跟踪如下:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-15-f1d8a31726e2> in <module>()
22 estimator = tf.keras.estimator.model_to_estimator(model)
23
---> 24 estimator.train(input_fn, max_steps=1)
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/estimator/estimator.pyc in train(self, input_fn, hooks, steps, max_steps, saving_listeners)
374
375 saving_listeners = _check_listeners_type(saving_listeners)
--> 376 loss = self._train_model(input_fn, hooks, saving_listeners)
377 logging.info('Loss for final step: %s.', loss)
378 return self
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/estimator/estimator.pyc in _train_model(self, input_fn, hooks, saving_listeners)
1143 return self._train_model_distributed(input_fn, hooks, saving_listeners)
1144 else:
-> 1145 return self._train_model_default(input_fn, hooks, saving_listeners)
1146
1147 def _train_model_default(self, input_fn, hooks, saving_listeners):
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/estimator/estimator.pyc in _train_model_default(self, input_fn, hooks, saving_listeners)
1168 worker_hooks.extend(input_hooks)
1169 estimator_spec = self._call_model_fn(
-> 1170 features, labels, model_fn_lib.ModeKeys.TRAIN, self.config)
1171 return self._train_with_estimator_spec(estimator_spec, worker_hooks,
1172 hooks, global_step_tensor,
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/estimator/estimator.pyc in _call_model_fn(self, features, labels, mode, config)
1131
1132 logging.info('Calling model_fn.')
-> 1133 model_fn_results = self._model_fn(features=features, **kwargs)
1134 logging.info('Done calling model_fn.')
1135
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/estimator/keras.pyc in model_fn(features, labels, mode)
357 """model_fn for keras Estimator."""
358 model = _clone_and_build_model(mode, keras_model, custom_objects, features,
--> 359 labels)
360 model_output_names = []
361 # We need to make sure that the output names of the last layer in the model
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/estimator/keras.pyc in _clone_and_build_model(mode, keras_model, custom_objects, features, labels)
313 model = models.clone_model(keras_model, input_tensors=input_tensors)
314 else:
--> 315 model = models.clone_model(keras_model, input_tensors=input_tensors)
316 else:
317 model = keras_model
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/keras/models.pyc in clone_model(model, input_tensors)
261 return _clone_sequential_model(model, input_tensors=input_tensors)
262 else:
--> 263 return _clone_functional_model(model, input_tensors=input_tensors)
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/keras/models.pyc in _clone_functional_model(model, input_tensors)
154 kwargs['mask'] = computed_mask
155 output_tensors = generic_utils.to_list(layer(computed_tensor,
--> 156 **kwargs))
157 output_masks = generic_utils.to_list(
158 layer.compute_mask(computed_tensor, computed_mask))
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/keras/engine/base_layer.pyc in __call__(self, inputs, *args, **kwargs)
718
719 # Check input assumptions set before layer building, e.g. input rank.
--> 720 self._assert_input_compatibility(inputs)
721 if input_list and self._dtype is None:
722 try:
.../anaconda2/lib/python2.7/site-packages/tensorflow/python/keras/engine/base_layer.pyc in _assert_input_compatibility(self, inputs)
1438 ', found ndim=' + str(ndim) +
1439 '. Full shape received: ' +
-> 1440 str(x.shape.as_list()))
1441 # Check dtype.
1442 if spec.dtype is not None:
ValueError: Input 0 of layer logits is incompatible with the layer: : expected min_ndim=2, found ndim=1. Full shape received: [None]
1 回答
我终于设法弄清楚如何使用
model_to_estimator
与TFHub嵌入 . 您需要在Keras模型之外进行嵌入 . 您的Keras模型必须将嵌入作为输入,而不是在模型中处理嵌入 . 但是,您可以将Keras模型用作估算函数中的函数 .例如,您可以定义接受预先计算嵌入的Keras模型(对于此示例,我希望嵌入返回序列而不是单个平均嵌入,因此输入形状具有序列长度):
您将定义估算器模型函数,而不是编译此模型然后使用
model_to_estimator
,例如:像这样调用Keras模型可以从模型中获得计算出的logits . 然后你可以返回一个
tf.estimator.EstimatorSpec
来创建一个Estimatorm abd然后从那里训练 .你可以参考the Tensorflow MNIST example看看它们如何围绕Keras模型包装Tensorflow计算以创建估计模型函数然后估算器,即使它们没有使用TFHub中的任何东西 .