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Stanford Parser processes raw text in English, Chinese, German, Arabic, and French, and extracts constituency parse trees.
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package edu.stanford.nlp.parser.nndep;

import edu.stanford.nlp.ling.CoreAnnotations;
import edu.stanford.nlp.ling.CoreLabel;
import edu.stanford.nlp.trees.PennTreebankLanguagePack;
import edu.stanford.nlp.trees.TreebankLanguagePack;
import edu.stanford.nlp.util.CollectionUtils;
import edu.stanford.nlp.util.CoreMap;
import edu.stanford.nlp.util.logging.Redwood;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Defines a transition-based parsing framework for dependency parsing.
 *
 * @author Danqi Chen
 */
public abstract class ParsingSystem  {

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

  /**
   * Defines language-specific settings for this parsing instance.
   */
  private final TreebankLanguagePack tlp;

  /**
   * Dependency label used between root of sentence and ROOT node.
   */
  protected final String rootLabel;

  protected final List labels, transitions;

  /**
   * Determine whether the given transition is legal for this
   * configuration.
   *
   * @param c Parsing configuration
   * @param t Transition string
   * @return Whether the given transition is legal in this
   *         configuration
   */
  public abstract boolean canApply(Configuration c, String t);

  /**
   * Apply the given transition to the given configuration, modifying
   * the configuration's state in place.
   */
  public abstract void apply(Configuration c, String t);

  /**
   * Provide a static-oracle recommendation for the next parsing step
   * to take.
   *
   * @param c Current parser configuration
   * @param dTree Gold tree which parser needs to reach
   * @return Transition string
   */
  public abstract String getOracle(Configuration c, DependencyTree dTree);

  /**
   * Determine whether applying the given transition in the given
   * configuration tree will leave in us a state in which we can reach
   * the gold tree. (Useful for building a dynamic oracle.)
   */
  abstract boolean isOracle(Configuration c, String t, DependencyTree dTree);

  /**
   * Build an initial parser configuration from the given sentence.
   */
  public abstract Configuration initialConfiguration(CoreMap sentence);

  /**
   * Determine if the given configuration corresponds to a parser which
   * has completed its parse.
   */
  abstract boolean isTerminal(Configuration c);

  /**
   * Return the number of transitions.
   */
  public int numTransitions() {
    return transitions.size();
  }

  // TODO pass labels as Map; use GrammaticalRelation throughout

  /**
   * @param tlp TreebankLanguagePack describing the language being
   *            parsed
   * @param labels A list of possible dependency relation labels, with
   *               the ROOT relation label as the first element
   */
  public ParsingSystem(TreebankLanguagePack tlp, List labels, List transitions, boolean verbose) {
    this.tlp = tlp;
    this.labels = new ArrayList<>(labels);
    //NOTE: assume that the first element of labels is rootLabel
    rootLabel = labels.get(0);
    this.transitions = transitions;

    if (verbose) {
      log.info(Config.SEPARATOR);
      log.info("#Transitions: " + numTransitions());
      log.info("#Labels: " + labels.size());
      log.info("ROOTLABEL: " + rootLabel);
    }
  }

  public int getTransitionID(String s) {
    int numTrans = numTransitions();
    for (int k = 0; k < numTrans; ++k) {
      if (transitions.get(k).equals(s)) {
        return k;
      }
    }
    return -1;
  }

  private Set getPunctuationTags() {
    if (tlp instanceof PennTreebankLanguagePack) {
      // Hack for English: match punctuation tags used in Danqi's paper
      return new HashSet<>(Arrays.asList("''", ",", ".", ":", "``", "-LRB-", "-RRB-"));
    } else {
      return CollectionUtils.asSet(tlp.punctuationTags());
    }
  }

  /**
   * Evaluate performance on a list of sentences, predicted parses,
   * and gold parses.
   *
   * @return A map from metric name to metric value
   */
  public Map evaluate(List sentences, List trees,
                                      List goldTrees) {
    Map result = new HashMap<>();

    // We'll skip words which are punctuation. Retrieve tags indicating
    // punctuation in this treebank.
    Set punctuationTags = getPunctuationTags();

    if (trees.size() != goldTrees.size()) {
      log.error("Incorrect number of trees.");
      return null;
    }

    int correctArcs = 0;
    int correctArcsNoPunc = 0;
    int correctHeads = 0;
    int correctHeadsNoPunc = 0;

    int correctTrees = 0;
    int correctTreesNoPunc = 0;
    int correctRoot = 0;

    int sumArcs = 0;
    int sumArcsNoPunc = 0;

    for (int i = 0; i < trees.size(); ++i) {
      List tokens = sentences.get(i).get(CoreAnnotations.TokensAnnotation.class);

      if (trees.get(i).n != goldTrees.get(i).n) {
        log.error("Tree " + (i + 1) + ": incorrect number of nodes.");
        return null;
      }
      if (!trees.get(i).isTree()) {
        log.error("Tree " + (i + 1) + ": illegal.");
        return null;
      }

      int nCorrectHead = 0;
      int nCorrectHeadNoPunc = 0;
      int nNoPunc = 0;

      for (int j = 1; j <= trees.get(i).n; ++j) {
        if (trees.get(i).getHead(j) == goldTrees.get(i).getHead(j)) {
          ++correctHeads;
          ++nCorrectHead;
          if (trees.get(i).getLabel(j).equals(goldTrees.get(i).getLabel(j)))
            ++correctArcs;
        }
        ++sumArcs;

        String tag = tokens.get(j - 1).tag();
        if (!punctuationTags.contains(tag)) {
          ++sumArcsNoPunc;
          ++nNoPunc;
          if (trees.get(i).getHead(j) == goldTrees.get(i).getHead(j)) {
            ++correctHeadsNoPunc;
            ++nCorrectHeadNoPunc;
            if (trees.get(i).getLabel(j).equals(goldTrees.get(i).getLabel(j)))
              ++correctArcsNoPunc;
          }
        }
      }
      if (nCorrectHead == trees.get(i).n)
        ++correctTrees;
      if (nCorrectHeadNoPunc == nNoPunc)
        ++correctTreesNoPunc;
      if (trees.get(i).getRoot() == goldTrees.get(i).getRoot())
        ++correctRoot;
    }

    result.put("UAS", correctHeads * 100.0 / sumArcs);
    result.put("UASnoPunc", correctHeadsNoPunc * 100.0 / sumArcsNoPunc);
    result.put("LAS", correctArcs * 100.0 / sumArcs);
    result.put("LASnoPunc", correctArcsNoPunc * 100.0 / sumArcsNoPunc);

    result.put("UEM", correctTrees * 100.0 / trees.size());
    result.put("UEMnoPunc", correctTreesNoPunc * 100.0 / trees.size());
    result.put("ROOT", correctRoot * 100.0 / trees.size());


    return result;
  }

  public double getUAS(List sentences, List trees, List goldTrees) {
    Map result = evaluate(sentences, trees, goldTrees);
    return result == null || !result.containsKey("UAS") ? -1.0 : result.get("UAS");
  }

  public double getUASnoPunc(List sentences, List trees, List goldTrees) {
    Map result = evaluate(sentences, trees, goldTrees);
    return result == null || !result.containsKey("UASnoPunc") ? -1.0 : result.get("UASnoPunc");
  }

}