Formal models and scripts: numeric-string-version-utils

Tools: SMT-LIB (Z3/cvc5), 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

• MathUtil.asinh, acosh and atanh use the textbook log formulas without range reduction: asinh and acosh return Infinity for every finite |x| >= 2^512, asinh and atanh return 0 for tiny nonzero x, and acosh of a large negative x returns an infinity instead of the documented NaN, also through the expression functions asinh, acosh and atanh (finding LFV-327; repro · finding page)
• RamUsageEstimator.sizeOfCollection adds the assumed backing-array bytes in int arithmetic, so a collection of 536,870,908 or more elements (268,435,453 with 8-byte references) gets a size estimate that is a multiple of 4 GiB too low, and negative when the elements add little (finding LFV-323; repro · finding page)

Files

• mathutil-inverse-hyperbolic-range-collapse/model/ref_error.py (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/p1_probe_overflow_sat.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/p2_probe_asinh_zero_sat.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/p3_probe_atanh_zero_sat.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/q1_overflow_all_large.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/q2_overflow_tight.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/q3_asinh_zero_all_small.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/q4_asinh_zero_tight.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/q5_atanh_zero_all_small.smt2 (used for LFV-327)
• mathutil-inverse-hyperbolic-range-collapse/model/smt-hyperbolic/q6_atanh_zero_tight.smt2 (used for LFV-327)
• ramusage-sizeofcollection-int-overflow/model/collection_overflow.py (used for LFV-323)

How to run

• SMT-LIB: z3 <file>.smt2 or cvc5 <file>.smt2 (sat with a model is a counterexample where the query asks for one).
• 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.