stanfordnlp/CoreNLP · error · UnsupportedOperationException

Doesn't do k best yet

Error message

Doesn't do k best yet

What it means

ExhaustiveDependencyParser implements the ParserQuery interface but does not support extracting the exact k best parses. getKBestParses(int) is a stub that unconditionally throws UnsupportedOperationException. The parser only computes a single Viterbi-style best parse.

Solutions

1. Use ExhaustivePCFGParser (or another k-best capable parser) instead of ExhaustiveDependencyParser when k-best output is needed.
2. Wrap the call in a try-catch for UnsupportedOperationException and degrade to getBestParse().
3. Check interface capability before calling; call getBestParse() for the single best dependency parse.

Example fix

// before
List<ScoredObject<Tree>> parses = pq.getKBestParses(10);
// after
List<ScoredObject<Tree>> parses;
try {
  parses = pq.getKBestParses(10);
} catch (UnsupportedOperationException e) {
  parses = Collections.singletonList(new ScoredObject<>(pq.getBestParse(), pq.getBestScore()));
}

// k-best capability check
if (query.getClass().getSimpleName().contains("ExhaustiveDependencyParser")) {
  throw new IllegalArgumentException("k-best not supported by this parser");
}

try { parses = pq.getKBestParses(k); } catch (UnsupportedOperationException e) { parses = Collections.singletonList(new ScoredObject<>(pq.getBestParse(), pq.getBestScore())); }

When it happens

Trigger: Calling getKBestParses(k) on a ParserQuery produced by ExhaustiveDependencyParser, e.g. via parserQuery.getKBestParses(10) after a successful parse.

Common situations: Code written against a shared ParserQuery/BiLexiconizedParser interface that assumes k-best support, but configured with a dependency grammar / ExhaustiveDependencyParser factory instead of ExhaustivePCFGParser.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Doesn't do best parses yet
• Doesn't do k good yet
• Doesn't do k sampled yet
• ExhaustivePCFGParser doesn't sample.
• FastFactoredParser: cannot provide k good parses.

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/7805da370dcd01ad. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/parser/lexparser/ExhaustiveDependencyParser.java:820

    iPossibleByR = new boolean[length + 1][length + 1][tagNum];
    oPossibleByL = new boolean[length + 1][length + 1][tagNum];
    oPossibleByR = new boolean[length + 1][length + 1][tagNum];
    headScore = new float[dg.numDistBins()][length][tagNum][length][tagNum];
    headStop = new float[length + 1][tagNum][length + 1];
    rawDistance = new int[length + 1][length + 1];
    binDistance = new int[length + 1][length + 1];
  }

  /** Get the exact k best parses for the sentence.
   *
   *  @param k The number of best parses to return
   *  @return The exact k best parses for the sentence, with
   *         each accompanied by its score (typically a
   *         negative log probability).
   */
  @Override
  public List<ScoredObject<Tree>> getKBestParses(int k) {
    throw new UnsupportedOperationException("Doesn't do k best yet");
  }

  /** Get a complete set of the maximally scoring parses for a sentence,
   *  rather than one chosen at random.  This set may be of size 1 or larger.
   *
   *  @return All the equal best parses for a sentence, with each
   *         accompanied by its score
   */
  @Override
  public List<ScoredObject<Tree>> getBestParses() {
    throw new UnsupportedOperationException("Doesn't do best parses yet");
  }

  /** Get k good parses for the sentence.  It is expected that the
   *  parses returned approximate the k best parses, but without any
   *  guarantee that the exact list of k best parses has been produced.
   *  If a class really provides k best parses functionality, it is
   *  reasonable to also return this output as the k good parses.

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