Using tf.keras.utils.Sequence with model.fit_generator with use_multiprocessing=True generated warning

Question

This is the warning I got:

WARNING:tensorflow:multiprocessing can interact badly with TensorFlow, causing nondeterministic deadlocks. For high performance data pipelines tf.data is recommended.

The Sequence subclass I wrote strictly perform load and read I/O jpg files. I guess as long as no 2 threads do it simultaneously on the same file, things should be ok.

I trained for a few epoch and so far, there's no error. But would like to get feedback if there's something potentially bad that could happen.

Answer 1

Initially in the TensorFlow 2.0 Version, there were issues with the keras.utils.Sequence with multiprocessing=True was causing a hang due to deadlock. Later in Tensorflow 2.1 this Warning was added to address this concern.

# use_multiprocessing=False works.
# use_multiprocessing=True hangs in a deadlock situation.
model.fit_generator(generator, use_multiprocessing=True, workers=2)  

You can ignore this warning since you are not doing any processing which will create deadlock situation.