code: package zemberek.core.embeddings;
  
  import com.google.common.base.Stopwatch;
  import com.google.common.eventbus.EventBus;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Path;
  import java.util.Iterator;
  import java.util.List;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CompletionService;
  import java.util.concurrent.ExecutorCompletionService;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicLong;
  import zemberek.core.collections.IntVector;
  import zemberek.core.logging.Log;
  import zemberek.core.text.BlockTextLoader;
  import zemberek.core.text.TextChunk;
  import zemberek.core.text.TextIO;
  
  public class FastTextTrainer {
  
    private static EventBus eventBus = new EventBus();
  
    public EventBus getEventBus() {
      return eventBus;
    }
  
    private Args args_;
  
    public FastTextTrainer(Args args) {
      this.args_ = args;
    }
  
    /**
     * Trains a model for the input with given arguments, returns a FastText instance. Input can be a
     * text corpus, or a corpus with text and labels.
     */
    public FastText train(Path input) throws Exception {
  
      Dictionary dict_ = Dictionary.readFromFile(input, args_);
      Matrix input_ = null;
      if (args_.pretrainedVectors.length() != 0) {
        //TODO: implement this.
        //loadVectors(args_->pretrainedVectors);
      } else {
        input_ = new Matrix(dict_.nwords() + args_.bucket, args_.dim);
        input_.uniform(1.0f / args_.dim);
      }
  
      Matrix output_;
      if (args_.model == Args.model_name.supervised) {
        output_ = new Matrix(dict_.nlabels(), args_.dim);
      } else {
        output_ = new Matrix(dict_.nwords(), args_.dim);
      }
  
      Model model_ = new Model(input_, output_, args_, 0);
      if (args_.model == Args.model_name.supervised) {
        model_.setTargetCounts(dict_.getCounts(Dictionary.TYPE_LABEL));
      } else {
        model_.setTargetCounts(dict_.getCounts(Dictionary.TYPE_WORD));
      }
  
      Stopwatch stopwatch = Stopwatch.createStarted();
      AtomicLong tokenCount = new AtomicLong(0);
  
      ExecutorService es = Executors.newFixedThreadPool(args_.thread);
      CompletionService<Model> completionService = new ExecutorCompletionService<>(es);
      long charCount = TextIO.charCount(input, StandardCharsets.UTF_8);
      Log.info("Training started.");
      Stopwatch sw = Stopwatch.createStarted();
      for (int i = 0; i < args_.thread; i++) {
        // Here a model per thread is generated. It uses references to global model's input and output matrices.
        // AFAIK, original Fasttext does not care about thread safety of those matrices.
        Model threadModel = new Model(model_, i);
  
        completionService.submit(new TrainTask(
            i,
            input,
            (int) (i * charCount / args_.thread),
            threadModel,
            stopwatch,
            dict_,
            args_,
            tokenCount));
      }
      es.shutdown();
  
      int c = 0;
      while (c < args_.thread) {
        completionService.take().get();
        c++;
      }
      return new FastText(args_, dict_, model_);
    }
  
    public static class Progress {
  
      public long total;
      public long current;
      public float percentProgress;
      public float wordsPerSecond;
      public float learningRate;
      public float loss;
      public String eta;
  
      public Progress(float percentProgress, float wordsPerSecond, float learningRate, float loss,
          String eta) {
        this.percentProgress = percentProgress;
        this.wordsPerSecond = wordsPerSecond;
        this.learningRate = learningRate;
        this.loss = loss;
        this.eta = eta;
      }
    }
  
    private static class TrainTask implements Callable<Model> {
  
      int threadId;
      Path input;
      int startCharIndex;
      Stopwatch stopwatch;
      AtomicLong tokenCount;
      Model model;
      Dictionary dictionary;
      Args args_;
  
      TrainTask(int threadId,
          Path input,
          int startCharIndex,
          Model model,
          Stopwatch stopwatch,
          Dictionary dictionary,
          Args args_,
          AtomicLong tokenCount) {
        this.threadId = threadId;
        this.input = input;
        this.startCharIndex = startCharIndex;
        this.model = model;
        this.stopwatch = stopwatch;
        this.tokenCount = tokenCount;
        this.dictionary = dictionary;
        this.args_ = args_;
      }
  
      private void printInfo(float progress, float loss) {
        float t = stopwatch.elapsed(TimeUnit.MILLISECONDS) / 1000f;
        float wst = (float) tokenCount.get() / t;
        float lr = (float) (args_.lr * (1.0f - progress));
        int eta = (int) (t / progress * (1 - progress) / args_.thread);
        int etah = eta / 3600;
        int etam = (eta - etah * 3600) / 60;
  
        Progress p = new Progress(
            100 * progress,
            wst,
            lr,
            loss,
            String.format("%dh%dm", etah, etam)
        );
        p.total = args_.epoch * dictionary.ntokens();
        p.current = tokenCount.get();
  
        eventBus.post(p);
  
      }
  
      private void supervised(Model model,
          float lr,
          int[] line,
          int[] labels) {
        if (labels.length == 0 || line.length == 0) {
          return;
        }
        int i = model.getRng().nextInt(labels.length);
        model.update(line, labels[i], lr);
      }
  
      private void cbow(Model model, float lr, int[] line) {
        for (int w = 0; w < line.length; w++) {
          int boundary = model.getRng().nextInt(args_.ws) + 1; // [1..args.ws]
          IntVector bow = new IntVector();
          for (int c = -boundary; c <= boundary; c++) {
            if (c != 0 && w + c >= 0 && w + c < line.length) {
              int[] ngrams = dictionary.getSubWords(line[w + c]);
              bow.addAll(ngrams);
            }
          }
          model.update(bow.copyOf(), line[w], lr);
        }
      }
  
      private void skipgram(Model model, float lr, int[] line) {
        for (int w = 0; w < line.length; w++) {
          int boundary = model.getRng().nextInt(args_.ws) + 1; // [1..args.ws]
          int[] ngrams = dictionary.getSubWords(line[w]);
          for (int c = -boundary; c <= boundary; c++) {
            if (c != 0 && w + c >= 0 && w + c < line.length) {
              model.update(ngrams, line[w + c], lr);
            }
          }
        }
      }
  
      @Override
      public Model call() {
  
        if (args_.model == Args.model_name.supervised) {
          model.setTargetCounts(dictionary.getCounts(Dictionary.TYPE_LABEL));
        } else {
          model.setTargetCounts(dictionary.getCounts(Dictionary.TYPE_WORD));
        }
  
        long ntokens = dictionary.ntokens();
        long localTokenCount = 0;
  
        Iterator<TextChunk> it = BlockTextLoader
            .iteratorFromCharIndex(input, 1000, startCharIndex);
        float progress = 0f;
        while (true) {
          while (it.hasNext()) {
            List<String> lines = it.next().getData();
            for (String lineStr : lines) {
              if (tokenCount.get() >= args_.epoch * ntokens) {
                if (threadId == 0 && args_.verbose > 0) {
                  printInfo(1.0f, model.getLoss());
                }
                return model;
              }
              IntVector line = new IntVector(15);
              progress = (float) ((1.0 * tokenCount.get()) / (args_.epoch * ntokens));
              float lr = (float) (args_.lr * (1.0 - progress));
  
              if (args_.model == Args.model_name.supervised) {
                IntVector labels = new IntVector();
                localTokenCount += dictionary.getLine(lineStr, line, labels);
                supervised(model, lr, line.copyOf(), labels.copyOf());
              } else if (args_.model == Args.model_name.cbow) {
                localTokenCount += dictionary.getLine(lineStr, line, model.getRng());
                cbow(model, lr, line.copyOf());
              } else if (args_.model == Args.model_name.skipGram) {
                localTokenCount += dictionary.getLine(lineStr, line, model.getRng());
                skipgram(model, lr, line.copyOf());
              }
              if (localTokenCount > args_.lrUpdateRate) {
                tokenCount.getAndAdd(localTokenCount);
                localTokenCount = 0;
              }
            }
            if (threadId == 0 && args_.verbose > 1) {
              printInfo(progress, model.getLoss());
            }
          }
          // start from the beginning again.
          it = BlockTextLoader.singlePathIterator(input, 1000);
        }
      }
    }
  
  
  }
  