Formal models and scripts: memory-bitset-collector-manager

Tools: TLA+/TLC

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

• MemoryAccountingBitsetCollector sizes each collector's bitset to the doc-id span of its slice, so under concurrent search a slice whose segments are not adjacent in doc-id order allocates, and charges to the memory tracker, bits for the segments that other slices search (finding LFV-348; repro)

Files

• model/MABC.tla (used for LFV-348)

How to run

• TLA+ with TLC: java -cp tla2tools.jar tlc2.TLC -config <Model>.cfg <Model>.tla (a counterexample trace is the finding when the model encodes the current code).

Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.