validation_data: Data on which to evaluate the loss and any model metrics at the end of each epoch. The model will not be trained on this data. Thus, note the fact that the validation loss of data provided using validation_split or validation_data is not affected by regularization layers like noise and dropout. validation_data will override validation_split. validation_data could be: - A tuple (x_val, y_val) of Numpy arrays or tensors. - A tuple (x_val, y_val, val_sample_weights) of NumPy arrays. - A tf.data.Dataset. - A Python generator or keras.utils.Sequence returning (inputs, targets) or (inputs, targets, sample_weights). validation_data is not yet supported with tf.distribute.experimental.ParameterServerStrategy.