accentuk

The offline Python package. The Docker service (stress API, lexicon database, TTS frontend, UI) is vacuum-in/accentuk-api.

Offline Ukrainian stress marking and TTS text verbalization powered by a memory-mapped MARISA lexicon and deep neural disambiguation.

accentuk runs completely locally without network calls at inference time. It offers two first-class operational modes: Light (CTranslate2 INT8 quantized, ~150 MB RAM, ultra-low latency) and Full (PyTorch FP32 + spaCy TRF + learned Combiner, maximum ensemble coverage).

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Operating Modes: Light vs. Full

Metric / Capability	Light Mode (mode="light")	Full Mode (mode="full")	Benefit of Light
Lexicon Lookup	MARISA BytesTrie (lexicon.marisa)	MARISA BytesTrie (lexicon.marisa)	Zero-copy mmap (<10 µs/word)
Deterministic Rules	Prepositions, compounds, suffix analogy table	Prepositions, compounds, suffix analogy table	Identical deterministic rules
Cross-Encoder Model	CTranslate2 INT8 (267 MB)	PyTorch FP32 XLM-RoBERTa (1,061 MB)	3.1x faster, 74.8% smaller
Token Classifier	CTranslate2 INT8 (106 MB)	PyTorch FP32 XLM-RoBERTa (420 MB)	6.0x faster, 74.7% smaller
TTS Verbalizer	CTranslate2 INT8 (51 MB, 4.4 ms/sentence)	PyTorch FP32 MarianMT (200 MB, 2.9 s/sentence)	660x faster, 74.3% smaller
Morphology Tier	spaCy small (uk_core_news_sm, ~15 MB)	spaCy TRF (uk_core_news_trf_380, 380 MB)	small CPU tagger
Total Model Disk	425 MB	~1,680 MB (+ 380 MB spaCy)	74.7% disk reduction
Runtime Memory (RSS)	~120 – 180 MB	~1,500 – 2,200 MB	~10x lower RAM
Recommended For	Production TTS, embedded systems, CLI, microservices	Research, batch indexing, maximum ensemble accuracy

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Installation

pip install accentuk

Optional TTS verbalization support:

pip install "accentuk[tts]"

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Quick Start (Python API)

1. Stress Marking (Accentor)

from accentuk import Accentor

# Light mode: fast CTranslate2 INT8 models, low memory footprint
with Accentor(mode="light") as engine:
    result = engine.stress("Замок стоїть на горі.")
    print(result.text)  # "За́мок стої́ть на горі́."
    for token in result.tokens:
        print(f"{token.text} -> {token.output_text} ({token.status})")

# Full mode: PyTorch FP32 models + spaCy TRF + Combiner
with Accentor(mode="full") as engine:
    result = engine.stress("Замок стоїть на горі.")
    print(result.text)

# Auto mode (default): uses Light if CT2 models exist, otherwise Full/Dictionary
with Accentor(mode="auto") as engine:
    result = engine.stress("Мої сестри.")
    print(result.text)  # "Мої́ се́стри."

2. TTS Normalization & Stress Marking (Frontend)

Normalizes dates, numbers, currencies, abbreviations, and symbols, then applies stress marks:

from accentuk import Frontend

# Light mode: fast INT8 verbalization (4.4 ms) + Light stress marking
with Frontend(mode="light") as frontend:
    result = frontend.prepare("Вона купила 25 яблук за 150 грн 3 квітня 2024 року.")
    print(result.text)

# Full mode: MarianMT PyTorch FP32 + Full stress marking
with Frontend(mode="full") as frontend:
    result = frontend.prepare("Вона купила 25 яблук за 150 грн 3 квітня 2024 року.")
    print(result.text)

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CLI Usage

Downloading Model Assets

Download the appropriate bundle for your target environment:

# Download Light assets (~425 MB CT2 INT8 models + lexicon)
accentuk download --light

# Download Full assets (~2.2 GB PyTorch weights + spaCy TRF + lexicon)
accentuk download --full

# Download with TTS verbalizer included
accentuk download --light --tts
accentuk download --full --tts

Stress Marking from CLI

# Stress plain Ukrainian text using Light mode
accentuk stress "Замок на горі стоїть." --mode light

# Stress using Full mode
accentuk stress "Замок на горі стоїть." --mode full

# Process text from standard input
echo "Мої сестри." | accentuk stress --mode light

TTS Normalization from CLI

accentuk prepare "О 7:45 ранку 3 квітня потяг № 12 прибув до Києва." --mode light

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Accuracy

Measured on 2026-10-13 with the same benchmarks as the service (vacuum-in/accentuk-api), word accuracy:

test	service	full mode	light mode
200 most frequent ambiguous forms of Common Voice uk, stress heard in the recordings	95.88%	95.88%	95.54%
modern-text gold, 3,887 words (all / reviewed lines)	98.07% / 96.83%	98.07% / 96.83%	97.63% / 96.25%
lang-uk stress benchmark, words / heteronyms	96.10% / 84.62%	96.10% / 84.62%	96.10% / 84.62%

The lexicon accentuk download installs (lexicon-v2, built from the public data-v2 of accentuk-api) is the service's, including the 51,298-word dictionary of stress heard in recordings; the light-mode column was measured on a clean download of it.

Full mode gives the service's answers. Light mode differs on 34 lang-uk tokens: 18 where the small spaCy tagger parses differently from the transformer one, the rest from INT8 quantization (the INT8 cross-encoder picks another reading than FP32 on 2.1% of targets; its margins track FP32 with r = 0.984, so the served threshold 0.5 is kept).

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Benchmark Results

Evaluated on AMD EPYC / Intel Xeon CPUs with single-thread and batched execution:

Model Tier	PyTorch FP32 Latency	CTranslate2 INT8 Latency	Speedup	Quality Parity
Verbalizer (MarianMT)	2,891 ms / sentence	4.38 ms / sentence	659.9x	100% exact match
Token Classifier (XLM-R-uk)	31.0 ms / target	5.20 ms / target	5.96x	100% top-1 match
Cross-Encoder (XLM-R)	100.2 ms / target	32.6 ms / target	3.07x	96.0% top-1 match

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Disambiguation Pipeline

When a word has multiple possible accents (heteronym), accentuk resolves stress through sequential tiers:

1. Memory-Mapped Lexicon: Exact form lookup via MARISA Trie (lexicon.marisa).
2. Capitalization & Proper Noun Rules: Differentiates names and toponyms (e.g. Розді́л vs. ро́зділ).
3. Prepositional Pronoun Shift: Shifts accent to the first syllable after governing prepositions (e.g. без ньо́го, до ме́не).
4. Contextual Cross-Encoder: Evaluates sentence context against candidate senses (aloudreader/uk-stress-crossencoder).
5. Token Classifier: Direct sequence labeling trained on audiobook audio alignment (aloudreader/uk-stress-token-classifier).
6. Morphology & Agreement Rules: Grammatical tags and case/number agreements (spaCy TRF in Full mode).
7. Dictionary Defaults & Fallbacks: Trie defaults, compound splitting (пшенично-житній), and analogy-based suffix tables.

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License

Apache-2.0. See LICENSE and NOTICE.md for third-party component licenses and dataset attributions.