log_dir="logs/fit/" + datetime.datetime.now().strftime("%Y%m%d-%H%M%S")
tensorboard_callback = tf.keras.callbacks.TensorBoard(log_dir=log_dir)
callback_list = [tensorboard_callback]

# start training
model.fit(train_generator,
                    epochs=EPOCHS,
                    steps_per_epoch=train_num // BATCH_SIZE,
                    validation_data=valid_generator,
                    validation_steps=valid_num // BATCH_SIZE,
                    callbacks=callback_list,
                    verbose=0)

# save the whole model
model.save(model_dir)

%tensorboard --logdir logs/fit