I'm making my first steps learning TF and have some trouble training RNNs.
My toy problem goes like this: a two layers LSTM + dense layer network is fed with raw audio data and should test whether a certain frequency is present in the sound.
so the network should 1 to 1 map float(audio data sequence) to float(pre-chosen frequency volume)
I've got this to work on Keras and seen a similar TFLearn solution but would like to implement this on bare Tensorflow in a relatively efficient way.
what i've done:
lstm = rnn_cell.BasicLSTMCell(LSTM_SIZE,state_is_tuple=True,forget_bias=1.0)
lstm = rnn_cell.DropoutWrapper(lstm)
stacked_lstm = rnn_cell.MultiRNNCell([lstm] * 2,state_is_tuple=True)
outputs, states = rnn.dynamic_rnn(stacked_lstm, in, dtype=tf.float32)
outputs = tf.transpose(outputs, [1, 0, 2])
last = tf.gather(outputs, int(outputs.get_shape()[0]) - 1)
network= tf.matmul(last, W) + b
# cost function, optimizer etc...
during training I fed this with (BATCH_SIZE, SEQUENCE_LEN,1) batches and it seems like the loss converged correctly but I can't figure out how to predict with the trained network.
My (awful lot of) questions:
how do i make this network return a sequence right from Tensorflow without going back to python for each sample(feed a sequence and predict a sequence of the same size)?
If I do want to predict one sample at a time and iterate in python what is the correct way to do it?
During testing is dynamic_rnn needed or it's just used for unrolling for BPTT during training? why is dynamic_rnn returning all the back propagation steps Tensors? these are the outputs of each layer of the unrolled network right?
after some research:
how do i make this network return a sequence right from Tensorflow
without going back to python for each sample(feed a sequence and
predict a sequence of the same size)?
you can use state_saving_rnn
class Saver():
def __init__(self):
self.d = {}
def state(self, name):
if not name in self.d:
return tf.zeros([1,LSTM_SIZE],tf.float32)
return self.d[name]
def save_state(self, name, val):
self.d[name] = val
return tf.identity('save_state_name') #<-important for control_dependencies
outputs, states = rnn.state_saving_rnn(stacked_lstm, inx, Saver(),
('lstmstate', 'lstmstate2', 'lstmstate3', 'lstmstate4'),sequence_length=[EVAL_SEQ_LEN])
#4 states are for two layers of lstm each has hidden and CEC variables to restore
network = [tf.matmul(outputs[-1], W) for i in xrange(EVAL_SEQ_LEN)]
one problem is that state_saving_rnn is using rnn() and not dynamic_rnn() therefore unroll at compile time EVAL_SEQ_LEN steps you might want to re-implement state_saving_rnn with dynamic_rnn if you want to input long sequences
If I do want to predict one sample at a time and iterate in python what is the correct way to do it?
you can use dynamic_rnn and supply initial_state. this is probably just as efficient as state_saving_rnn. look at state_saving_rnn implementations for reference
During testing is dynamic_rnn needed or it's just used for unrolling for BPTT during training? why is dynamic_rnn returning all the back propagation steps Tensors? these are the outputs of each layer of the unrolled network right?
dynamic_rnn does do unrolling at runtime similarly to compile time rnn(). I guess it returns all the steps for you to branch the graph in some other places - after less time steps. in a network that use [one time step input * current state -> one output, new state] like the one described above it's not needed in testing but could be used for training truncated time back propagation
Related
I have a simpleRNN / LSTM that I'm trying to train on a sequential classification task using tensorflow. There is a sequence of data (300 time steps) that predicts a label at t=300. For my task I would like for the RNN to evaluate the error at every timestep (not just at the final time point) and propagate it backwards (as figure below).
After some responses below it seems I need to do a few things: use return_sequences flag; use the TimeDistributed layer to access the output from the LSTM/RNN; and also defined a custom loss function.
model = Sequential()
layer1 = LSTM(n_neurons, input_shape=(length, 1), return_sequences=True)
model.add(layer1)
layer2 = TimeDistributed(Dense(1))
model.add(layer2)
# Define custom loss
def custom_loss(layer1):
# Create a loss function
def loss(y_true,y_pred):
# access layer1 at every time point and compute mean error
# UNCLEAR HOW TO RUN AT EVERY TIME STEP
err = K.mean(layer1(X) - y_true, axis=-1)
return err
# Return a function
return loss
# Compile the model
model.compile(optimizer='adam', loss=custom_loss(layer), metrics=['accuracy'])
For now I'm a bit confused of the custom_loss function as it's not clear that how I can pass in layer1 and compute the error inside the inner most loss function.
Anyone has a suggestion or can point me to a more detailed answer?
The question is not easy to answer since it is not clear what you're trying to achieve (it shouldn't be the same using a FFNN or a RNN, and what works best depends definitely on the application).
Anyway, you might be confusing the training steps (say, the forward- and back- propagation over a minibatch of sequences) with the "internal" steps of the RNN. A single sequence (or a single minibatch) will always "unroll" entirely through time during the forward pass before any output is made available: only after (thus, at the end of the training step), you can use the predictions and compute the losses to backpropagate.
What you can do is return sequences of outputs (one y_predicted for every internal time step) including the argument return_sequences=True inside SimpleRNN(...). This will give you a sequence of 300 predictions, each of which depends only on the past inputs with respect to the considered internal time step. You can then use the outputs that you need to compute the loss, possibly in a custom loss function.
I hope I've been clear enough. Otherwise, let me know if I can help further.
I am trying to convert my CNN written with tensorflow layers to use the keras api in tensorflow (I am using the keras api provided by TF 1.x), and am having issue writing a custom loss function, to train the model.
According to this guide, when defining a loss function it expects the arguments (y_true, y_pred)
https://www.tensorflow.org/guide/keras/train_and_evaluate#custom_losses
def basic_loss_function(y_true, y_pred):
return ...
However, in every example I have seen, y_true is somehow directly related to the model (in the simple case it is the output of the network). In my problem, this is not the case. How do implement this if my loss function depends on some training data that is unrelated to the tensors of the model?
To be concrete, here is my problem:
I am trying to learn an image embedding trained on pairs of images. My training data includes image pairs and annotations of matching points between the image pairs (image coordinates). The input feature is only the image pairs, and the network is trained in a siamese configuration.
I am able to implement this successfully with tensorflow layers and train it sucesfully with tensorflow estimators.
My current implementations builds a tf Dataset from a large database of tf Records, where the features is a dictionary containing the images and arrays of matching points. Before I could easily feed these arrays of image coordinates to the loss function, but here it is unclear how to do so.
There is a hack I often use that is to calculate the loss within the model, by means of Lambda layers. (When the loss is independent from the true data, for instance, and the model doesn't really have an output to be compared)
In a functional API model:
def loss_calc(x):
loss_input_1, loss_input_2 = x #arbirtray inputs, you choose
#according to what you gave to the Lambda layer
#here you use some external data that doesn't relate to the samples
externalData = K.constant(external_numpy_data)
#calculate the loss
return the loss
Using the outputs of the model itself (the tensor(s) that are used in your loss)
loss = Lambda(loss_calc)([model_output_1, model_output_2])
Create the model outputting the loss instead of the outputs:
model = Model(inputs, loss)
Create a dummy keras loss function for compilation:
def dummy_loss(y_true, y_pred):
return y_pred #where y_pred is the loss itself, the output of the model above
model.compile(loss = dummy_loss, ....)
Use any dummy array correctly sized regarding number of samples for training, it will be ignored:
model.fit(your_inputs, np.zeros((number_of_samples,)), ...)
Another way of doing it, is using a custom training loop.
This is much more work, though.
Although you're using TF1, you can still turn eager execution on at the very beginning of your code and do stuff like it's done in TF2. (tf.enable_eager_execution())
Follow the tutorial for custom training loops: https://www.tensorflow.org/tutorials/customization/custom_training_walkthrough
Here, you calculate the gradients yourself, of any result regarding whatever you want. This means you don't need to follow Keras standards of training.
Finally, you can use the approach you suggested of model.add_loss.
In this case, you calculate the loss exaclty the same way I did in the first answer. And pass this loss tensor to add_loss.
You can probably compile a model with loss=None then (not sure), because you're going to use other losses, not the standard one.
In this case, your model's output will probably be None too, and you should fit with y=None.
my problem is the following:
I am working on an object detection problem and would like to use dropout during test time to obtain a distribution of outputs. The object detection network consists of a training model and a prediction model, which wraps around the training model. I would like to perform several stochastic forward passes using the training model and combine these e.g. by averaging the predictions in the prediction wrapper. Is there a way of doing this in a keras model instead of requiring an intermediate processing step using numpy?
Note that this question is not about how to enable dropout during test time
def prediction_wrapper(model):
# Example code.
# Arguments
# model: the training model
regression = model.outputs[0]
classification = model.outputs[1]
predictions = # TODO: perform several stochastic forward passes (dropout during train and test time) here
avg_predictions = # TODO: combine predictions here, e.g. by computing the mean
outputs = # TODO: do some processing on avg_predictions
return keras.models.Model(inputs=model.inputs, outputs=outputs, name=name)
I use keras with a tensorflow backend.
I appreciate any help!
The way I understand, you're trying to average the weight updates for a single sample while Dropout is enabled. Since dropout is random, you would get different weight updates for the same sample.
If this understanding is correct, then you could create a batch by duplicating the same sample. Here I am assuming that the Dropout is different for each sample in a batch. Since, backpropagation averages the weight updates anyway, you would get your desired behavior.
If that does not work, then you could write a custom loss function and train with a batch-size of one. You could update a global counter inside your custom loss function and return non-zero loss only when you've averaged them the way you want it. I don't know if this would work, it's just an idea.
I am still relatively new to the world of Deep Learning. I wanted to create a Deep Learning model (preferably using Tensorflow/Keras) for image anomaly detection. By anomaly detection I mean, essentially a OneClassSVM.
I have already tried sklearn's OneClassSVM using HOG features from the image. I was wondering if there is some example of how I can do this in deep learning. I looked up but couldn't find one single code piece that handles this case.
The way of doing this in Keras is with the KerasRegressor wrapper module (they wrap sci-kit learn's regressor interface). Useful information can also be found in the source code of that module. Basically you first have to define your Network Model, for example:
def simple_model():
#Input layer
data_in = Input(shape=(13,))
#First layer, fully connected, ReLU activation
layer_1 = Dense(13,activation='relu',kernel_initializer='normal')(data_in)
#second layer...etc
layer_2 = Dense(6,activation='relu',kernel_initializer='normal')(layer_1)
#Output, single node without activation
data_out = Dense(1, kernel_initializer='normal')(layer_2)
#Save and Compile model
model = Model(inputs=data_in, outputs=data_out)
#you may choose any loss or optimizer function, be careful which you chose
model.compile(loss='mean_squared_error', optimizer='adam')
return model
Then, pass it to the KerasRegressor builder and fit with your data:
from keras.wrappers.scikit_learn import KerasRegressor
#chose your epochs and batches
regressor = KerasRegressor(build_fn=simple_model, nb_epoch=100, batch_size=64)
#fit with your data
regressor.fit(data, labels, epochs=100)
For which you can now do predictions or obtain its score:
p = regressor.predict(data_test) #obtain predicted value
score = regressor.score(data_test, labels_test) #obtain test score
In your case, as you need to detect anomalous images from the ones that are ok, one approach you can take is to train your regressor by passing anomalous images labeled 1 and images that are ok labeled 0.
This will make your model to return a value closer to 1 when the input is an anomalous image, enabling you to threshold the desired results. You can think of this output as its R^2 coefficient to the "Anomalous Model" you trained as 1 (perfect match).
Also, as you mentioned, Autoencoders are another way to do anomaly detection. For this I suggest you take a look at the Keras Blog post Building Autoencoders in Keras, where they explain in detail about the implementation of them with the Keras library.
It is worth noticing that Single-class classification is another way of saying Regression.
Classification tries to find a probability distribution among the N possible classes, and you usually pick the most probable class as the output (that is why most Classification Networks use Sigmoid activation on their output labels, as it has range [0, 1]). Its output is discrete/categorical.
Similarly, Regression tries to find the best model that represents your data, by minimizing the error or some other metric (like the well-known R^2 metric, or Coefficient of Determination). Its output is a real number/continuous (and the reason why most Regression Networks don't use activations on their outputs). I hope this helps, good luck with your coding.
I'm new to TensorFlow and am getting a bit tripped up on the mechanics of reading data. I set up a TensorFlow graph on the mnist data, but I'd like to modify it so that I can run one program to train it + save the model out, and run another to load said graph, make predictions, and compute test accuracy.
Where I'm getting confused is how to bypass the original I/O system in the training graph and "inject" an image to predict or an (image, label) tuple of test data for accuracy testing. To read the training data, I'm using this code:
_, input_data = util.read_examples(
paths_to_files,
batch_size,
shuffle=shuffle,
num_epochs=None)
feature_map = {
'label': tf.FixedLenFeature(
shape=[], dtype=tf.int64, default_value=[-1]),
'image': tf.FixedLenFeature(
shape=[NUM_PIXELS * NUM_PIXELS], dtype=tf.int64),
}
example = tf.parse_example(input_data, features=feature_map)
I then feed example to a convolution layer, etc. and generate the output.
Now imagine that I train my graph with that code specifying the input, save out the graph and weights, and then restore the graph and weights in another script for prediction -- I'd like to take (say) 10 images and feed them to the graph to generate predictions. How do I "inject" those 10 images so that the predictions come out the other end?
I played around with feed dictionaries and placeholders, but I'm not sure if they're the right things for me to use... it seems like they rely on having data in memory, as opposed to reading from a queue of test data, for example.
Thanks!
A feed dictionary with placeholders would make sense if you wanted to perform a small number of inferences/evaluations (i.e. enough to fit in memory) - e.g. if you were serving a simple model or running small eval loops.
If you specifically want to infer or evaluate large batches then you should use the same approach you've used for training, but with a different path to your test/eval/live data. e.g.
_, eval_data = util.read_examples(
paths_to_files, # CHANGE THIS BIT
batch_size,
shuffle=shuffle,
num_epochs=None)
You can use this as a normal python variable and set up successive, dependent steps to use this as a provided variable. e.g.
def get_example(data):
return tf.parse_example(data, features=feature_map)
sess.run([get_example(path_to_your_data)])