stanfordnlp/CoreNLP · error · IllegalArgumentException

Input array with 0 rows

Error message

Input array with 0 rows

What it means

ConvertModels.toMatrix converts a List<List<Double>> into a SimpleMatrix but rejects empty input: calling it with a list containing zero rows throws IllegalArgumentException('Input array with 0 rows'). The neural model conversion code requires at least one row to infer matrix dimensions.

Solutions

1. Check the input list is non-empty before calling toMatrix
2. Verify the source model file is not empty or corrupt
3. Regenerate the feature lists so at least one row is produced

Example fix

// before
SimpleMatrix m = ConvertModels.toMatrix(rows); // rows may be empty
// after
if (rows.isEmpty()) { throw new IllegalStateException("no rows to convert"); }
SimpleMatrix m = ConvertModels.toMatrix(rows);

if (rows == null || rows.isEmpty()) {
  throw new IllegalArgumentException("toMatrix requires at least one row");
}

try {
  SimpleMatrix m = ConvertModels.toMatrix(rows);
} catch (IllegalArgumentException e) {
  if (e.getMessage().contains("0 rows")) {
    logger.warning("empty model features; skipping conversion");
    return;
  }
  throw e;
}

When it happens

Trigger: Calling toMatrix with an empty List (in.size()==0), typically via toTensor, f, antecedentMatrix, anaphorMatrix, pairFeaturesMatrix, or pairwiseFirstLayerBias when a model file yields no feature rows.

Common situations: Converting an empty/corrupt serialized model (e.g. empty word-vector or sentiment model file) during legacy-to-new model conversion, or a preprocessing step that filtered out all entries.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Input array with 0 columns
• Input array with uneven columns
• Attempt to make ObjectBank with empty file list
• Can't parse a zero-length sentence!
• No matching files

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/0a2e4f1b20dba805. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/neural/ConvertModels.java:80

      }
    }

    return out;
  }

  public static List<List<List<Double>>> fromTensor(SimpleTensor in) {
    List<List<List<Double>>> out = new ArrayList<>();

    for (int i = 0; i < in.numSlices(); ++i) {
      out.add(fromMatrix(in.getSlice(i)));
    }

    return out;
  }

  public static SimpleMatrix toMatrix(List<List<Double>> in) {
    if (in.size() == 0) {
      throw new IllegalArgumentException("Input array with 0 rows");
    }
    if (in.get(0).size() == 0) {
      throw new IllegalArgumentException("Input array with 0 columns");
    }
    for (int i = 1; i < in.size(); ++i) {
      if (in.get(i).size() != in.get(0).size()) {
        throw new IllegalArgumentException("Input array with uneven columns");
      }
    }

    SimpleMatrix out = new SimpleMatrix(in.size(), in.get(0).size());
    for (int i = 0; i < in.size(); ++i) {
      List<Double> row = in.get(i);
      for (int j = 0; j < row.size(); ++j) {
        out.set(i, j, row.get(j));
      }
    }

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