How to log Keras loss output to a file

Question

When you run a Keras neural network model you might see something like this in the console:

Epoch 1/3
   6/1000 [..............................] - ETA: 7994s - loss: 5111.7661

As time goes on the loss hopefully improves. I want to log these losses to a file over time so that I can learn from them. I have tried:

logging.basicConfig(filename='example.log', filemode='w', level=logging.DEBUG)

but this doesn't work. I am not sure what level of logging I need in this situation.

I have also tried using a callback like in:

def generate_train_batch():
    while 1:
        for i in xrange(0,dset_X.shape[0],3):
            yield dset_X[i:i+3,:,:,:],dset_y[i:i+3,:,:]

class LossHistory(keras.callbacks.Callback):
    def on_train_begin(self, logs={}):
        self.losses = []

    def on_batch_end(self, batch, logs={}):
        self.losses.append(logs.get('loss'))
logloss=LossHistory()
colorize.fit_generator(generate_train_batch(),samples_per_epoch=1000,nb_epoch=3,callbacks=['logloss'])

but obviously this isn't writing to a file. Whatever the method, through a callback or the logging module or anything else, I would love to hear your solutions for logging loss of a keras neural network to a file. Thanks!

Answer 1

There is a simple solution to your problem. Every time any of the fit methods are used - as a result the special callback called History Callback is returned. It has a field history which is a dictionary of all metrics registered after every epoch. So to get list of loss function values after every epoch you can easly do:

history_callback = model.fit(params...)
loss_history = history_callback.history["loss"]

It's easy to save such list to a file (e.g. by converting it to numpy array and using savetxt method).

UPDATE:

Try:

import numpy
numpy_loss_history = numpy.array(loss_history)
numpy.savetxt("loss_history.txt", numpy_loss_history, delimiter=",")

UPDATE 2:

The solution to the problem of recording a loss after every batch is written in Keras Callbacks Documentation in a Create a Callback paragraph.

Answer 2

You can use CSVLogger callback.

as example:

from keras.callbacks import CSVLogger

csv_logger = CSVLogger('log.csv', append=True, separator=';')
model.fit(X_train, Y_train, callbacks=[csv_logger])

Look at: Keras Callbacks

Answer 3

Old question, but here goes. Keras history output perfectly matches pandas DataSet input.

If you want the entire history to csv in one line: pandas.DataFrame(model.fit(...).history).to_csv("history.csv")

Cheers

Answer 4

You can redirect the sys.stdout object to a file before the model.fit method and reassign it to the standard console after model.fit method as follows:

import sys
oldStdout = sys.stdout
file = open('logFile', 'w')
sys.stdout = file
model.fit(Xtrain, Ytrain)
sys.stdout = oldStdout