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Stanford CoreNLP provides a set of natural language analysis tools which can take raw English language text input and give the base forms of words, their parts of speech, whether they are names of companies, people, etc., normalize dates, times, and numeric quantities, mark up the structure of sentences in terms of phrases and word dependencies, and indicate which noun phrases refer to the same entities. It provides the foundational building blocks for higher level text understanding applications.

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// CRFClassifier -- a probabilistic (CRF) sequence model, mainly used for NER.
// Copyright (c) 2002-2008 The Board of Trustees of
// The Leland Stanford Junior University. All Rights Reserved.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// For more information, bug reports, fixes, contact:
//    Christopher Manning
//    Dept of Computer Science, Gates 1A
//    Stanford CA 94305-9010
//    USA
//    Support/Questions: [email protected]
//    Licensing: [email protected]

package edu.stanford.nlp.ie.crf; 
import edu.stanford.nlp.util.logging.Redwood;

import edu.stanford.nlp.ling.CoreAnnotations;
import edu.stanford.nlp.objectbank.ObjectBank;
import edu.stanford.nlp.sequences.*;
import edu.stanford.nlp.util.*;

import java.util.*;

/**
 * Subclass of CRFClassifier that performs dropout feature-noising training.
 *
 * @author Mengqiu Wang
 */
public class CRFClassifierWithDropout extends CRFClassifier  {

  /** A logger for this class */
  private static Redwood.RedwoodChannels log = Redwood.channels(CRFClassifierWithDropout.class);

  private List> unsupDocs;

  public CRFClassifierWithDropout(SeqClassifierFlags flags) {
    super(flags);
  }


  @Override
  protected Collection> loadAuxiliaryData(Collection> docs, DocumentReaderAndWriter readerAndWriter) {
    if (flags.unsupDropoutFile != null) {
      log.info("Reading unsupervised dropout data from file: " + flags.unsupDropoutFile);
      Timing timer = new Timing();
      timer.start();
      unsupDocs = new ArrayList<>();
      ObjectBank> unsupObjBank = makeObjectBankFromFile(flags.unsupDropoutFile, readerAndWriter);
      for (List doc : unsupObjBank) {
        for (IN tok: doc) {
          tok.set(CoreAnnotations.AnswerAnnotation.class, flags.backgroundSymbol);
          tok.set(CoreAnnotations.GoldAnswerAnnotation.class, flags.backgroundSymbol);
        }
        unsupDocs.add(doc);
      }
      long elapsedMs = timer.stop();
      log.info("Time to read: : " + Timing.toSecondsString(elapsedMs) + " seconds");
    }
    if (unsupDocs != null && flags.doFeatureDiscovery) {
      List> totalDocs = new ArrayList<>();
      totalDocs.addAll(docs);
      totalDocs.addAll(unsupDocs);
      return totalDocs;
    } else
      return docs;
  }

  @Override
  protected CRFLogConditionalObjectiveFunction getObjectiveFunction(int[][][][] data, int[][] labels) {
    int[][][][] unsupDropoutData = null;
    if (unsupDocs != null) {
      Timing timer = new Timing();
      timer.start();
      List> unsupDataAndLabels = documentsToDataAndLabelsList(unsupDocs);
      unsupDropoutData = new int[unsupDataAndLabels.size()][][][];
      for (int q=0; q