seq2seq_model.py 文件源码

def compute_loss(self, decoder_output, _features, labels):
    """Computes the loss for this model.

    Returns a tuple `(losses, loss)`, where `losses` are the per-batch
    losses and loss is a single scalar tensor to minimize.
    """
    #pylint: disable=R0201
    # Calculate loss per example-timestep of shape [B, T]
    losses = seq2seq_losses.cross_entropy_sequence_loss(
        logits=decoder_output.logits[:, :, :],
        targets=tf.transpose(labels["target_ids"][:, 1:], [1, 0]),
        sequence_length=labels["target_len"] - 1)

    # Calculate the average log perplexity
    loss = tf.reduce_sum(losses) / tf.to_float(
        tf.reduce_sum(labels["target_len"] - 1))

    return losses, loss