stanfordnlp/CoreNLP · error · IllegalArgumentException

Input array with 0 columns

Error message

Input array with 0 columns

What it means

ConvertModels.toMatrix rejects input where the first row has zero columns (in.get(0).size()==0), throwing IllegalArgumentException('Input array with 0 columns'). A matrix with rows but no columns cannot be dimensioned.

Solutions

1. Ensure each inner list has at least one element before calling toMatrix
2. Check the upstream feature extraction for rows that produce zero features
3. Inspect the source model serialization for empty vectors

Example fix

// before
SimpleMatrix m = ConvertModels.toMatrix(rows);
// after
if (rows.isEmpty() || rows.get(0).isEmpty()) { throw new IllegalStateException("row has 0 columns"); }
SimpleMatrix m = ConvertModels.toMatrix(rows);

if (rows == null || rows.isEmpty() || rows.get(0).isEmpty()) {
  throw new IllegalArgumentException("toMatrix requires at least one column in row 0");
}

static boolean hasColumns(java.util.List<java.util.List<Double>> rows) {
  return rows != null && !rows.isEmpty() && rows.get(0) != null && !rows.get(0).isEmpty();
}

try {
  SimpleMatrix m = ConvertModels.toMatrix(rows);
} catch (IllegalArgumentException e) {
  if (e.getMessage().contains("0 columns")) {
    throw new IllegalStateException("model rows have no features; check feature extraction", e);
  }
  throw e;
}

When it happens

Trigger: Calling toMatrix with a non-empty outer list whose first element is an empty List<Double>, e.g. antecedentMatrix/anaphorMatrix built from a model with no features per entry.

Common situations: Model files serialized with empty per-row vectors, or feature-extraction producing empty lists for every entry during model conversion.

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 rows
• 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/b6981906ad0067e0. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/neural/ConvertModels.java:83

    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));
      }
    }

    return out;
  }

View on GitHub (pinned to 1b7edd19c4)