Function decodeSequence

translation/translation.ts:294–351

Decode (i.e., translate) an encoded sentence. Args: input_seq: A `numpy.ndarray` of shape `(1, max_encoder_seq_length, num_encoder_tokens)`. encoder_model: A `keras.Model` instance for the encoder. decoder_model: A `keras.Model` instance for the decoder. num_decoder_tokens: Number of un

(
  inputSeq: tf.Tensor,
  encoderModel: tf.LayersModel,
  decoderModel: tf.LayersModel,
  numDecoderTokens: number,
  targetBeginIndex: number,
  reverseTargetCharIndex: {[indice: number]: string},
  maxDecoderSeqLength: number,
)

"""
*/
async function decodeSequence (
  inputSeq: tf.Tensor,
  encoderModel: tf.LayersModel,
  decoderModel: tf.LayersModel,
  numDecoderTokens: number,
  targetBeginIndex: number,
  reverseTargetCharIndex: {[indice: number]: string},
  maxDecoderSeqLength: number,
) {
  // Encode the input as state vectors.
  let statesValue = encoderModel.predict(inputSeq) as tf.Tensor[];

  // Generate empty target sequence of length 1.
  let targetSeq = tf.buffer<tf.Rank.R3>([
    1,
    1,
    numDecoderTokens,
  ]);

  // Populate the first character of target sequence with the start character.
  targetSeq.set(1, 0, 0, targetBeginIndex);

  // Sampling loop for a batch of sequences
  // (to simplify, here we assume a batch of size 1).
  let stopCondition = false;
  let decodedSentence = '';
  while (!stopCondition) {
    const [outputTokens, h, c] = decoderModel.predict(
      [targetSeq.toTensor(), ...statesValue]
    ) as [
      tf.Tensor<tf.Rank.R3>,
      tf.Tensor<tf.Rank.R2>,
      tf.Tensor<tf.Rank.R2>,
    ];

    // Sample a token
    const sampledTokenIndex =
        await outputTokens.squeeze().argMax(-1).array() as number;

    const sampledChar = reverseTargetCharIndex[sampledTokenIndex];
    decodedSentence += sampledChar;

    // Exit condition: either hit max length
    // or find stop character.
    if (sampledChar === '\n' ||
        decodedSentence.length > maxDecoderSeqLength) {
      stopCondition = true;
    }

    // Update the target sequence (of length 1).
    targetSeq = tf.buffer<tf.Rank.R3>([1, 1, numDecoderTokens], 'float32');
    targetSeq.set(1, 0, 0, sampledTokenIndex);

    // Update states
    statesValue = [h, c];
  }
  return decodedSentence;
}