Formal models and scripts: misc-reorder-split

Tools: Python

These are the working models and scripts this part of the hunt used. Some encode the code as it is (a counterexample is the expected result), others a fixed or correct variant; read the header comment of each file. Paths inside them were replaced by placeholders such as $LUCENE (a Lucene checkout) and $WORK.

Findings

• MultiPassIndexSplitter's round-robin split loses or duplicates the last few documents of an index at about IndexWriter.MAX_DOCS for most part counts of 145 or more, because its int test (j + numParts - i) % numParts overflows (finding LFV-531; repro · finding page)

Files

• multipass-splitter-round-robin-int-overflow/model/multipass_partition.py (used for LFV-531)
• multipass-splitter-round-robin-int-overflow/model/multipass_rr_overflow_exhaustive.py (used for LFV-531)

How to run

• Python: python3 <file>.py; scripts that import z3 need the z3-solver package.

Snapshot of 2026-11-03. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.