Formal models and scripts: study-similarity-impacts-smt

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

• AxiomaticF2LOG and AxiomaticF2EXP scores drop by 1 ulp as term frequency crosses a power of two (finding LFV-063; repro · finding page)
• IBSimilarity with DistributionLL returns -0.0f scores (finding LFV-072; repro · finding page)
• BaseSimilarityTestCase's 'scores don't decrease as terms get rarer' check is dead code (finding LFV-073; repro · finding page)

Files

• smt/axiomatic_f2.py
• smt/axiomatic_f2_fast.py
• smt/axiomatic_f2_narrow.py
• smt/axiomatic_f2_stage2.py
• smt/float_scorers.py
• smt/fpjava.py
• smt/impacts_bv.py
• smt/models.py
• smt/monotype.py
• smt/oplemmas.py
• smt/range_proofs.py
• smt/smtrun.py
• smt/translation_validate_f2.py

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.