Not benefiting from checkpointing

[mstfldmr]

Hello,

I save checkpoints with:

checkpoint_cb = tf.keras.callbacks.ModelCheckpoint(
  filepath = checkpoint_path + '/epoch-{epoch:02d}/',
  monitor = 'val_loss',
  save_freq = 'epoch',
  save_weights_only = False,
  save_best_only = False,
  mode = 'auto')

After loading the latest checkpoint and continuing training, I would expect the loss value to be around the loss value in the last checkpoint.

    model = tf.keras.models.load_model(
        model_path,
        custom_objects={"SimilarityModel": tfsim.models.SimilarityModel,
                        'MyOptimizer': tfa.optimizers.RectifiedAdam})

    model.load_index(model_path)

    model.fit(
        datasampler,
        callbacks = callbacks,
        epochs = args.epochs,
        initial_epoch=initial_epoch_number,
        steps_per_epoch = N_TRAIN_SAMPLES ,
        verbose=2
    )

However, the loss value does not continue from where it left. It looks like it's simply starting the training from scratch and not benefiting from checkpoints.

[owenvallis]

Thanks for submitting the issue @mstfldmr. Do you have a simple example I can use to try and repro the issue? I can also try and repro this using our basic example, but it might be good to get closer to your current set up as well.

[mstfldmr]

@owenvallis I'm sorry, I can't share the full code because it has some confidential pieces we developed. This was how I configured checkpointing:

checkpoint_cb = tf.keras.callbacks.ModelCheckpoint(checkpoint_path, monitor='loss', save_freq='epoch', save_weights_only=False, save_best_only=False)

and how I loaded a checkpoint back:

    resumed_model_from_checkpoints = tf.keras.models.load_model(f'{checkpoint_path}/{max_epoch_filename}')

[mstfldmr]

@owenvallis could you reproduce it?

[owenvallis]

Hi @mstfldmr, sorry for the delay here. I'll try and get to this this week.

[owenvallis]

Looking into this now as it also looks like there is a breaking change in 2.8 where they removed Optimizer.get_weights() (see https://github.com/keras-team/tf-keras/issues/442). That issue also mentions that SavedModel didn't properly save the weights for certain optimizers in the past (see https://github.com/tensorflow/tensorflow/issues/44670).

Which optimizer were you using? Was it Adam?

[mstfldmr]

@owenvallis yes, it was tfa.optimizers.RectifiedAdam.