krickert commented on PR #1003:
URL: https://github.com/apache/opennlp/pull/1003#issuecomment-4157829114
Summary since first review:
Made all 7 ME classes thread-safe by eliminating shared mutable instance
state. Deprecate the `ThreadSafe*ME` wrappers - users can now share ME
instances directly.
## Motivation
ME classes were documented as not thread-safe due to mutable instance fields
that corrupt under concurrent access. The workarounds were creating a new ME
instance per call (expensive) or using `ThreadSafe*ME` wrappers
(ThreadLocal-based, leak-prone in Jakarta EE). This PR makes the ME classes
themselves thread-safe, yielding a **2.52x throughput improvement** for
POSTagger (JMH, 32 threads) by enabling instance reuse.
## Approach
Mutable state moved to method-local variables or per-thread caches
(ThreadLocal) at every layer:
| Layer | Change
|
| ----------------------------------- |
--------------------------------------------------------------------------------------------------------------------------------
|
| **ME classes** (all 7) | Result fields (`bestSequence`,
`tokProbs`, etc.) made `volatile`; processing uses method-local variables with
atomic swap at end |
| **BeamSearch** | `probs[]` buffer and `contextsCache`
moved to per-thread `ThreadLocal` state
|
| **CachedFeatureGenerator** | Cache moved to per-thread
`ThreadLocal` (JMH confirms 1.62x benefit)
|
| **ConfigurablePOSContextGenerator** | Cache moved to per-thread
`ThreadLocal`
|
| **DefaultSDContextGenerator** | `buf`/`collectFeats` moved to
method-local parameters
|
### Files changed (30 total)
**Source (13 files):** TokenizerME, SentenceDetectorME, POSTaggerME,
LemmatizerME, ChunkerME, NameFinderME, LanguageDetectorME, BeamSearch,
CachedFeatureGenerator, ConfigurablePOSContextGenerator,
DefaultPOSContextGenerator, DefaultSDContextGenerator, SentenceContextGenerator
(Thai)
**Deprecated (7 files):** ThreadSafeTokenizerME,
ThreadSafeSentenceDetectorME, ThreadSafePOSTaggerME, ThreadSafeLemmatizerME,
ThreadSafeChunkerME, ThreadSafeNameFinderME, ThreadSafeLanguageDetectorME
**Internal usage swaps (3 files):** Muc6NameSampleStreamFactory,
TwentyNewsgroupSampleStreamFactory, POSTaggerMEIT - replaced `ThreadSafe*ME`
with direct ME usage
**Tests/benchmarks (5 files):** ThreadSafetyBenchmarkTest (8 JUnit tests), 3
JMH benchmarks, CachedFeatureGeneratorTest update
**Build (1 file):** pom.xml - fixed JMH annotation processor wiring
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