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/*
 * Copyright 2017-2022 John Snow Labs
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.johnsnowlabs.nlp.annotators.seq2seq

import com.johnsnowlabs.ml.ai.GPT2
import com.johnsnowlabs.ml.onnx.{OnnxWrapper, ReadOnnxModel, WriteOnnxModel}
import com.johnsnowlabs.ml.tensorflow.{
  ReadTensorflowModel,
  TensorflowWrapper,
  WriteTensorflowModel
}
import com.johnsnowlabs.ml.util.LoadExternalModel.{
  loadTextAsset,
  modelSanityCheck,
  notSupportedEngineError
}
import com.johnsnowlabs.ml.util.{ONNX, TensorFlow}
import com.johnsnowlabs.nlp.AnnotatorType.DOCUMENT
import com.johnsnowlabs.nlp._
import com.johnsnowlabs.nlp.annotators.tokenizer.bpe.{BpeTokenizer, Gpt2Tokenizer}
import com.johnsnowlabs.nlp.serialization.MapFeature
import org.apache.spark.broadcast.Broadcast
import org.apache.spark.ml.param._
import org.apache.spark.ml.util.Identifiable
import org.apache.spark.sql.SparkSession

/** GPT-2: the OpenAI Text-To-Text Transformer
  *
  * GPT-2 is a large transformer-based language model with 1.5 billion parameters, trained on a
  * dataset of 8 million web pages. GPT-2 is trained with a simple objective: predict the next
  * word, given all of the previous words within some text. The diversity of the dataset causes
  * this simple goal to contain naturally occurring demonstrations of many tasks across diverse
  * domains. GPT-2 is a direct scale-up of GPT, with more than 10X the parameters and trained on
  * more than 10X the amount of data.
  *
  * GPT-2 displays a broad set of capabilities, including the ability to generate conditional
  * synthetic text samples of unprecedented quality, where we prime the model with an input and
  * have it generate a lengthy continuation. In addition, GPT-2 outperforms other language models
  * trained on specific domains (like Wikipedia, news, or books) without needing to use these
  * domain-specific training datasets. On language tasks like question answering, reading
  * comprehension, summarization, and translation, GPT-2 begins to learn these tasks from the raw
  * text, using no task-specific training data. While scores on these downstream tasks are far
  * from state-of-the-art, they suggest that the tasks can benefit from unsupervised techniques,
  * given sufficient (unlabeled) data and compute.
  *
  * Pretrained models can be loaded with `pretrained` of the companion object:
  * {{{
  * val gpt2 = GPT2Transformer.pretrained()
  *   .setInputCols("document")
  *   .setOutputCol("generation")
  * }}}
  * The default model is `"gpt2"`, if no name is provided. For available pretrained models please
  * see the [[https://sparknlp.org/models?q=gpt2 Models Hub]].
  *
  * For extended examples of usage, see
  * [[https://github.com/JohnSnowLabs/spark-nlp/blob/master/src/test/scala/com/johnsnowlabs/nlp/annotators/seq2seq/GPT2TestSpec.scala GPT2TestSpec]].
  *
  * '''References:'''
  *   - [[https://d4mucfpksywv.cloudfront.net/better-language-models/language_models_are_unsupervised_multitask_learners.pdf Language Models are Unsupervised Multitask Learners]]
  *   - [[https://github.com/openai/gpt-2]]
  *
  * '''Paper Abstract:'''
  *
  * ''Natural language processing tasks, such as question answering, machine translation, reading
  * comprehension, and summarization, are typically approached with supervised learning on
  * taskspecific datasets. We demonstrate that language models begin to learn these tasks without
  * any explicit supervision when trained on a new dataset of millions of webpages called WebText.
  * When conditioned on a document plus questions, the answers generated by the language model
  * reach F1 on the CoQA dataset - matching or exceeding the performance of 3 out of 4 baseline
  * systems without using the 127,000+ training examples. The capacity of the language model is
  * essential to the success of zero-shot task transfer and increasing it improves performance in
  * a log-linear fashion across tasks. Our largest model, GPT-2, is a 1.5B parameter Transformer
  * that achieves state of the art results on 7 out of 8 tested language modeling datasets in a
  * zero-shot setting but still underfits WebText. Samples from the model reflect these
  * improvements and contain coherent paragraphs of text. These findings suggest a promising path
  * towards building language processing systems which learn to perform tasks from their naturally
  * occurring demonstrations.''
  *
  * '''Note:'''
  *
  * This is a very computationally expensive module especially on larger sequence. The use of an
  * accelerator such as GPU is recommended.
  *
  * ==Example==
  * {{{
  * import spark.implicits._
  * import com.johnsnowlabs.nlp.base.DocumentAssembler
  * import com.johnsnowlabs.nlp.annotators.seq2seq.GPT2Transformer
  * import org.apache.spark.ml.Pipeline
  *
  * val documentAssembler = new DocumentAssembler()
  *   .setInputCol("text")
  *   .setOutputCol("documents")
  *
  * val gpt2 = GPT2Transformer.pretrained("gpt2")
  *   .setInputCols(Array("documents"))
  *   .setMinOutputLength(10)
  *   .setMaxOutputLength(50)
  *   .setDoSample(false)
  *   .setTopK(50)
  *   .setNoRepeatNgramSize(3)
  *   .setOutputCol("generation")
  *
  * val pipeline = new Pipeline().setStages(Array(documentAssembler, gpt2))
  *
  * val data = Seq(
  *   "My name is Leonardo."
  * ).toDF("text")
  * val result = pipeline.fit(data).transform(data)
  *
  * results.select("generation.result").show(truncate = false)
  * +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  * |result                                                                                                                                                                                              |
  * +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  * |[ My name is Leonardo. I am a man of letters. I have been a man for many years. I was born in the year 1776. I came to the United States in 1776, and I have lived in the United Kingdom since 1776]|
  * +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
  * }}}
  *
  * @param uid
  *   required uid for storing annotator to disk
  * @groupname anno Annotator types
  * @groupdesc anno
  *   Required input and expected output annotator types
  * @groupname Ungrouped Members
  * @groupname param Parameters
  * @groupname setParam Parameter setters
  * @groupname getParam Parameter getters
  * @groupname Ungrouped Members
  * @groupprio param  1
  * @groupprio anno  2
  * @groupprio Ungrouped 3
  * @groupprio setParam  4
  * @groupprio getParam  5
  * @groupdesc param
  *   A list of (hyper-)parameter keys this annotator can take. Users can set and get the
  *   parameter values through setters and getters, respectively.
  */
class GPT2Transformer(override val uid: String)
    extends AnnotatorModel[GPT2Transformer]
    with HasBatchedAnnotate[GPT2Transformer]
    with ParamsAndFeaturesWritable
    with WriteTensorflowModel
    with WriteOnnxModel
    with HasEngine {

  def this() = this(Identifiable.randomUID("GPT2TRANSFORMER"))

  /** Input annotator type : DOCUMENT
    *
    * @group param
    */
  override val inputAnnotatorTypes: Array[AnnotatorType] = Array(DOCUMENT)

  /** Output annotator type : DOCUMENT
    *
    * @group param
    */
  override val outputAnnotatorType: String = DOCUMENT

  /** Set transformer task, e.g. `"summarize:"` (Default: `""`).
    *
    * @group param
    */
  val task = new Param[String](this, "task", "Set transformer task, e.g. 'summarize'")

  /** @group setParam */
  def setTask(value: String): GPT2Transformer.this.type = {
    if (get(task).isEmpty)
      set(task, value)
    this
  }

  /** Minimum length of the sequence to be generated (Default: `0`)
    *
    * @group param
    */
  val minOutputLength =
    new IntParam(this, "minOutputLength", "Minimum length of the sequence to be generated")

  /** @group setParam */
  def setMinOutputLength(value: Int): GPT2Transformer.this.type = {
    set(minOutputLength, value)
    this
  }

  /** @group getParam */
  def getMinOutputLength: Int = $(this.minOutputLength)

  /** Maximum length of the sequence to be generated (Default: `20`)
    *
    * @group param
    */
  val maxOutputLength =
    new IntParam(this, "maxOutputLength", "Maximum length of the sequence to be generated")

  /** @group setParam */
  def setMaxOutputLength(value: Int): GPT2Transformer.this.type = {
    set(maxOutputLength, value)
    this
  }

  /** @group getParam */
  def getMaxOutputLength: Int = $(this.maxOutputLength)

  /** Whether or not to use sampling, use greedy decoding otherwise (Default: `false`)
    *
    * @group param
    */
  val doSample = new BooleanParam(
    this,
    "doSample",
    "Whether or not to use sampling; use greedy decoding otherwise")

  /** @group setParam */
  def setDoSample(value: Boolean): GPT2Transformer.this.type = {
    set(doSample, value)
    this
  }

  /** @group getParam */
  def getDoSample: Boolean = $(this.doSample)

  /** The value used to module the next token probabilities (Default: `1.0`)
    *
    * @group param
    */
  val temperature =
    new DoubleParam(this, "temperature", "The value used to module the next token probabilities")

  /** @group setParam */
  def setTemperature(value: Double): GPT2Transformer.this.type = {
    set(temperature, value)
    this
  }

  /** @group getParam */
  def getTemperature: Double = $(this.temperature)

  /** The number of highest probability vocabulary tokens to keep for top-k-filtering (Default:
    * `50`)
    *
    * @group param
    */
  val topK = new IntParam(
    this,
    "topK",
    "The number of highest probability vocabulary tokens to keep for top-k-filtering")

  /** @group setParam */
  def setTopK(value: Int): GPT2Transformer.this.type = {
    set(topK, value)
    this
  }

  /** @group getParam */
  def getTopK: Int = $(this.topK)

  /** If set to float < `1.0`, only the most probable tokens with probabilities that add up to
    * `topP` or higher are kept for generation (Default: `1.0`)
    *
    * @group param
    */
  val topP = new DoubleParam(
    this,
    "topP",
    "If set to float < 1, only the most probable tokens with probabilities that add up to ``top_p`` or higher are kept for generation")

  /** @group setParam */
  def setTopP(value: Double): GPT2Transformer.this.type = {
    set(topP, value)
    this
  }

  /** @group getParam */
  def getTopP: Double = $(this.topP)

  /** The parameter for repetition penalty (Default: `1.0`). `1.0` means no penalty. See
    * [[https://arxiv.org/pdf/1909.05858.pdf this paper]] for more details.
    *
    * @group param
    */
  val repetitionPenalty = new DoubleParam(
    this,
    "repetitionPenalty",
    "The parameter for repetition penalty. 1.0 means no penalty.")

  /** @group setParam */
  def setRepetitionPenalty(value: Double): GPT2Transformer.this.type = {
    set(repetitionPenalty, value)
    this
  }

  /** @group getParam */
  def getRepetitionPenalty: Double = $(this.repetitionPenalty)

  /** If set to int > `0`, all ngrams of that size can only occur once (Default: `0`)
    *
    * @group param
    */
  val noRepeatNgramSize = new IntParam(
    this,
    "noRepeatNgramSize",
    "If set to int > 0, all ngrams of that size can only occur once")

  /** @group setParam */
  def setNoRepeatNgramSize(value: Int): GPT2Transformer.this.type = {
    set(noRepeatNgramSize, value)
    this
  }

  /** @group getParam */
  def getNoRepeatNgramSize: Int = $(this.noRepeatNgramSize)

  /** Optional Random seed for the model. Needs to be of type `Long`.
    *
    * @group param
    */
  var randomSeed: Option[Int] = None

  /** @group setParam */
  def setRandomSeed(value: Int): GPT2Transformer.this.type = {
    if (randomSeed.isEmpty) {
      this.randomSeed = Some(value)
    }
    this
  }

  /** @group getParam */
  def getRandomSeed: Option[Int] = this.randomSeed

  /** A list of token ids which are ignored in the decoder's output (Default: `Array()`)
    *
    * @group param
    */
  var ignoreTokenIds = new IntArrayParam(
    this,
    "ignoreTokenIds",
    "A list of token ids which are ignored in the decoder's output")

  /** @group setParam */
  def setIgnoreTokenIds(tokenIds: Array[Int]): GPT2Transformer.this.type = {
    set(ignoreTokenIds, tokenIds)
  }

  /** @group getParam */
  def getIgnoreTokenIds: Array[Int] = $(ignoreTokenIds)

  /** ConfigProto from tensorflow, serialized into byte array. Get with
    * config_proto.SerializeToString()
    *
    * @group param
    */
  val configProtoBytes = new IntArrayParam(
    this,
    "configProtoBytes",
    "ConfigProto from tensorflow, serialized into byte array. Get with config_proto.SerializeToString()")

  /** @group setParam */
  def setConfigProtoBytes(bytes: Array[Int]): GPT2Transformer.this.type =
    set(this.configProtoBytes, bytes)

  /** @group getParam */
  def getConfigProtoBytes: Option[Array[Byte]] = get(this.configProtoBytes).map(_.map(_.toByte))

  private var _tfModel: Option[Broadcast[GPT2]] = None

  /** Vocabulary used to encode the words to ids with bpeTokenizer.encode
    *
    * @group param
    */
  val vocabulary: MapFeature[String, Int] = new MapFeature(this, "vocabulary").setProtected()

  /** @group setParam */
  def setVocabulary(value: Map[String, Int]): this.type = set(vocabulary, value)

  /** Holding merges.txt coming from RoBERTa model
    *
    * @group param
    */
  val merges: MapFeature[(String, String), Int] = new MapFeature(this, "merges").setProtected()

  /** @group setParam */
  def setMerges(value: Map[(String, String), Int]): this.type = set(merges, value)

  /** @group setParam */
  def setModelIfNotSet(
      spark: SparkSession,
      tfWrapper: Option[TensorflowWrapper],
      onnxWrapper: Option[OnnxWrapper]): this.type = {
    if (_tfModel.isEmpty) {

      val bpeTokenizer = BpeTokenizer
        .forModel("gpt2", merges = $$(merges), vocab = $$(vocabulary))
        .asInstanceOf[Gpt2Tokenizer]

      _tfModel = Some(
        spark.sparkContext.broadcast(
          new GPT2(tfWrapper, onnxWrapper, bpeTokenizer, configProtoBytes = getConfigProtoBytes)))
    }
    this
  }

  /** @group getParam */
  def getModelIfNotSet: GPT2 = _tfModel.get.value

  setDefault(
    task -> "",
    minOutputLength -> 0,
    maxOutputLength -> 20,
    doSample -> false,
    temperature -> 1.0,
    topK -> 50,
    topP -> 1.0,
    repetitionPenalty -> 1.0,
    noRepeatNgramSize -> 3,
    ignoreTokenIds -> Array(),
    batchSize -> 4)

  /** takes a document and annotations and produces new annotations of this annotator's annotation
    * type
    *
    * @param batchedAnnotations
    *   Annotations that correspond to inputAnnotationCols generated by previous annotators if any
    * @return
    *   any number of annotations processed for every input annotation. Not necessary one to one
    *   relationship
    */
  override def batchAnnotate(batchedAnnotations: Seq[Array[Annotation]]): Seq[Seq[Annotation]] = {

    val allAnnotations = batchedAnnotations
      .filter(_.nonEmpty)
      .zipWithIndex
      .flatMap { case (annotations, i) =>
        annotations.filter(_.result.nonEmpty).map(x => (x, i))
      }
    val processedAnnotations = if (allAnnotations.nonEmpty) {
      this.getModelIfNotSet.predict(
        sentences = allAnnotations.map(_._1),
        batchSize = $(batchSize),
        minOutputLength = $(minOutputLength),
        maxOutputLength = $(maxOutputLength),
        doSample = $(doSample),
        temperature = $(temperature),
        topK = $(topK),
        topP = $(topP),
        repetitionPenalty = $(repetitionPenalty),
        noRepeatNgramSize = $(noRepeatNgramSize),
        task = $(task),
        randomSeed = this.randomSeed,
        ignoreTokenIds = $(ignoreTokenIds))
    } else {
      Seq()
    }

    // Group resulting annotations by rows. If there are not sentences in a given row, return empty sequence
    batchedAnnotations.indices.map(rowIndex => {
      val rowAnnotations = processedAnnotations
        // zip each annotation with its corresponding row index
        .zip(allAnnotations)
        // select the sentences belonging to the current row
        .filter(_._2._2 == rowIndex)
        // leave the annotation only
        .map(_._1)

      if (rowAnnotations.nonEmpty)
        rowAnnotations
      else
        Seq.empty[Annotation]
    })
  }

  override def onWrite(path: String, spark: SparkSession): Unit = {
    super.onWrite(path, spark)
    getEngine match {
      case TensorFlow.name =>
        writeTensorflowModelV2(
          path,
          spark,
          getModelIfNotSet.tensorflow.get,
          "_gpt2",
          GPT2Transformer.tfFile,
          configProtoBytes = getConfigProtoBytes)
      case ONNX.name =>
        writeOnnxModel(
          path,
          spark,
          getModelIfNotSet.onnxWrapper.get,
          "_gpt2",
          GPT2Transformer.onnxFile)
    }
  }
}

trait ReadablePretrainedGPT2TransformerModel
    extends ParamsAndFeaturesReadable[GPT2Transformer]
    with HasPretrained[GPT2Transformer] {
  override val defaultModelName: Some[String] = Some("gpt2")

  /** Java compliant-overrides */
  override def pretrained(): GPT2Transformer = super.pretrained()

  override def pretrained(name: String): GPT2Transformer = super.pretrained(name)

  override def pretrained(name: String, lang: String): GPT2Transformer =
    super.pretrained(name, lang)

  override def pretrained(name: String, lang: String, remoteLoc: String): GPT2Transformer =
    super.pretrained(name, lang, remoteLoc)
}

trait ReadGPT2TransformerDLModel extends ReadTensorflowModel with ReadOnnxModel {
  this: ParamsAndFeaturesReadable[GPT2Transformer] =>

  override val tfFile: String = "gpt2_tensorflow"
  override val onnxFile: String = "gpt2_onnx"

  def readModel(instance: GPT2Transformer, path: String, spark: SparkSession): Unit = {
    instance.getEngine match {
      case TensorFlow.name =>
        val tf = readTensorflowModel(path, spark, "_gpt2_tf")
        instance.setModelIfNotSet(spark, Some(tf), None)
      case ONNX.name =>
        val onnxWrapper =
          readOnnxModel(path, spark, "_gpt2_onnx", zipped = true, useBundle = false, None)
        instance.setModelIfNotSet(spark, None, Some(onnxWrapper))
    }
  }

  addReader(readModel)

  def loadSavedModel(modelPath: String, spark: SparkSession): GPT2Transformer = {

    val (localModelPath, detectedEngine) = modelSanityCheck(modelPath)

    val vocabs = loadTextAsset(localModelPath, "vocab.txt").zipWithIndex.toMap

    val bytePairs = loadTextAsset(localModelPath, "merges.txt")
      .map(_.split(" "))
      .filter(w => w.length == 2)
      .map { case Array(c1, c2) => (c1, c2) }
      .zipWithIndex
      .toMap

    /*Universal parameters for all engines*/
    val annotatorModel = new GPT2Transformer()
      .setVocabulary(vocabs)
      .setMerges(bytePairs)

    annotatorModel.set(annotatorModel.engine, detectedEngine)

    detectedEngine match {
      case TensorFlow.name =>
        val (wrapper, _) =
          TensorflowWrapper.read(
            localModelPath,
            zipped = false,
            useBundle = true,
            tags = Array("serve"))

        /** the order of setSignatures is important if we use getSignatures inside
          * setModelIfNotSet
          */
        annotatorModel
          .setModelIfNotSet(spark, Some(wrapper), None)

      case ONNX.name =>
        val onnxWrapper =
          OnnxWrapper.read(spark, localModelPath, zipped = false, useBundle = true)
        annotatorModel
          .setModelIfNotSet(spark, None, Some(onnxWrapper))
      case _ =>
        throw new Exception(notSupportedEngineError)
    }

    annotatorModel
  }

}

object GPT2Transformer
    extends ReadablePretrainedGPT2TransformerModel
    with ReadGPT2TransformerDLModel




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