JMTEB v2.0 - MTEB-Powered Japanese Text Embedding Benchmark

JMTEB v2.0 is a major update to the Japanese Massive Text Embedding Benchmark that integrates with the MTEB (Massive Text Embedding Benchmark) framework.

Overview

JMTEB v2.0 provides:

• 🌐 MTEB Compatibility: Integration with MTEB tools, leaderboards, and ecosystem
• 🚀 MTEB as Evaluation Engine: Leverage MTEB's robust framework
• 🎯 Simpler API: Cleaner, more intuitive interface
• 📊 28 Japanese Datasets: Comprehensive evaluation across 5 task types
• ⚡ High Performance: Efficient caching and batch processing

[!IMPORTANT] The leaderboard is now hosted on the MTEB Leaderboard (General Purpose → Language-specific → Japanese). We no longer maintain a separate leaderboard in this repository.

Quick Start

Installation

From source (Poetry):

# Clone the repository
git clone https://github.com/sbintuitions/JMTEB.git
cd JMTEB

# Default (v2.0 with OpenAI support)
poetry install

# With v1.x support
poetry install --extras v1

# With everything
poetry install --all-extras

[!NOTE] The package is not yet available on PyPI. Please install from source using the commands above.

Basic Usage

from jmteb.v2 import JMTEBModel, JMTEBV2Evaluator
from jmteb.v2.tasks import get_jmteb_tasks, get_jmteb_lite_benchmark

# Create model
model = JMTEBModel.from_sentence_transformer("cl-nagoya/ruri-v3-30m")

# Get datasets - Full JMTEB
tasks = get_jmteb_tasks()  # All 28 JMTEB datasets

# Or use JMTEB-lite for faster evaluation
# lite_benchmark = get_jmteb_lite_benchmark()
# tasks = lite_benchmark.tasks

# Evaluate
evaluator = JMTEBV2Evaluator(
    model=model,
    tasks=tasks,
    save_path="results_v2"
)
results = evaluator.run()

CLI Usage

# Evaluate all datasets
python -m jmteb.v2 --model_name cl-nagoya/ruri-v3-30m --save_path results_v2

# Evaluate specific datasets
python -m jmteb.v2 \
  --model_name cl-nagoya/ruri-v3-30m \
  --include JSTS JSICK JaqketRetrieval \
  --save_path results_v2

# Use prompts (e.g., for Ruri-v3 models)
python -m jmteb.v2 \
  --model_name cl-nagoya/ruri-v3-30m \
  --prompt_profile src/jmteb/configs/prompts/ruri-v3.yaml \
  --save_path results_v2

Architecture

Core Components

src/jmteb/v2/
├── __init__.py          # Main exports
├── __main__.py          # CLI entry point
├── adapters.py          # Model adapter (JMTEBModel)
├── evaluator.py         # Evaluation orchestrator
├── tasks.py             # Task definitions and utilities
└── utils.py             # Helper functions

Key Classes

1. JMTEBModel

Adapter that bridges models with MTEB's evaluation system.

from jmteb.v2 import JMTEBModel

# From HuggingFace via SentenceTransformer
model = JMTEBModel.from_sentence_transformer("cl-nagoya/ruri-v3-30m")

# From MTEB's unified model interface (recommended)
model = JMTEBModel.from_mteb("cl-nagoya/ruri-v3-30m")

2. JMTEBV2Evaluator

Orchestrates evaluation across multiple tasks.

from jmteb.v2 import JMTEBV2Evaluator

evaluator = JMTEBV2Evaluator(
    model=model,
    tasks=tasks,
    save_path="results_v2",
    batch_size=32,
    task_batch_sizes={"JSTS": 128},  # Per-task overrides
    overwrite_cache=False,
    generate_summary=True,
)
results = evaluator.run()

3. Task Utilities

Functions for working with JMTEB tasks.

from jmteb.v2.tasks import (
    get_jmteb_benchmark,
    get_jmteb_tasks,
    get_task_by_name,
    get_task_category,
)

# Get all datasets
all_tasks = get_jmteb_tasks()

# Filter by task type
retrieval_tasks = get_jmteb_tasks(task_types=["Retrieval"])

# Get specific datasets
specific_tasks = get_jmteb_tasks(task_names=["JSTS", "JSICK"])

# Get full benchmark
benchmark = get_jmteb_benchmark()

Task Coverage

JMTEB v2.0 includes 28 datasets across 5 task types.

JMTEB vs JMTEB-lite

• JMTEB (Full): Complete benchmark with full corpus sizes
• JMTEB-lite: Lightweight version with reduced corpus sizes for faster evaluation (~5x faster with high correlation to full JMTEB)

Both versions include the same 28 datasets:

Classification (7 datasets)

• AmazonReviewsClassification
• AmazonCounterfactualClassification
• MassiveIntentClassification
• MassiveScenarioClassification
• JapaneseSentimentClassification
• SIB200Classification
• WRIMEClassification

Clustering (3 datasets)

• LivedoorNewsClustering.v2
• MewsC16JaClustering
• SIB200ClusteringS2S

STS (2 datasets)

• JSTS
• JSICK

Retrieval (11 datasets)

• JaqketRetrieval (→ JaqketRetrievalLite in JMTEB-lite)
• MrTidyRetrieval (→ MrTyDiJaRetrievalLite in JMTEB-lite)
• JaGovFaqsRetrieval
• NLPJournalTitleAbsRetrieval.V2
• NLPJournalTitleIntroRetrieval.V2
• NLPJournalAbsIntroRetrieval.V2
• NLPJournalAbsArticleRetrieval.V2
• JaCWIRRetrieval (→ JaCWIRRetrievalLite in JMTEB-lite)
• MIRACLRetrieval (→ MIRACLJaRetrievalLite in JMTEB-lite)
• MintakaRetrieval
• MultiLongDocRetrieval

Reranking (5 datasets)

• ESCIReranking
• JQaRAReranking (→ JQaRARerankingLite in JMTEB-lite)
• JaCWIRReranking (→ JaCWIRRerankingLite in JMTEB-lite)
• MIRACLReranking
• MultiLongDocReranking

Features

1. Prompt Support

Configure prompts for models that require them (e.g., E5):

# src/jmteb/configs/prompts/e5.yaml
query: "query: "
document: "passage: "

from jmteb.v2.utils import load_prompts

prompts = load_prompts("src/jmteb/configs/prompts/e5.yaml")
model = JMTEBModel.from_sentence_transformer(
    "intfloat/multilingual-e5-base",
    prompts=prompts
)

2. Batch Size Configuration

Different tasks have varying memory requirements (e.g., retrieval tasks with long documents need smaller batches to avoid OOM), so per-task batch size configuration helps optimize performance.

# batch_sizes.yaml
JSTS: 128
JSICK: 128
JaqketRetrieval: 32
MIRACLRetrieval: 16
MultiLongDocRetrieval: 8

from jmteb.v2.utils import load_batch_sizes

batch_sizes = load_batch_sizes("batch_sizes.yaml")
evaluator = JMTEBV2Evaluator(
    model=model,
    tasks=tasks,
    task_batch_sizes=batch_sizes
)

3. Result Caching

Results are automatically cached to avoid re-evaluation:

# First run: evaluates all tasks
evaluator.run()

# Second run: loads from cache
evaluator.run()  # Instant!

# Force re-evaluation
evaluator = JMTEBV2Evaluator(
    model=model,
    tasks=tasks,
    overwrite_cache=True
)
evaluator.run()

4. Summary Generation

Automatically generates summary.json with main scores:

{
  "Classification": {
    "amazon_review_classification": {
      "main_metric": "accuracy",
      "main_score": 67.32,
      "eval_time (s)": "12.34"
    }
  },
  "STS": {
    "jsts": {
      "main_metric": "cosine_spearman",
      "main_score": 82.14,
      "eval_time (s)": "5.67"
    }
  }
}

5. Progress Tracking

Real-time progress updates during evaluation:

[1/28] Task: JSTS (batch_size=128)
--------------------------------------------------------------------------------
✓ Completed: JSTS (time: 5.67s)
  → Updated summary: STS/jsts = 82.14 (time: 5.67s)

[2/28] Task: JSICK (batch_size=128)
--------------------------------------------------------------------------------
✓ Loaded from cache: JSICK
  → Updated summary: STS/jsick = 76.89 (cached)

Advanced Usage

Custom Model Implementation

Implement your own model by following the encode interface:

import numpy as np
from jmteb.v2 import JMTEBModel

class CustomModel:
    def encode(self, sentences: list[str], batch_size: int = 32, **kwargs) -> np.ndarray:
        # Your encoding logic here
        embeddings = your_model.encode(sentences)
        return np.array(embeddings)

# Wrap for JMTEB v2
model = JMTEBModel(sentence_transformer=CustomModel())

Dataset-Specific Evaluation

Evaluate subsets of datasets:

from jmteb.v2.tasks import get_jmteb_tasks

# Only datasets from STS task
sts_tasks = get_jmteb_tasks(task_types=["STS"])

# Specific retrieval datasets
retrieval_tasks = get_jmteb_tasks(
    task_names=["JaqketRetrieval", "MIRACLRetrieval"]
)

# All classification datasets
classification_tasks = get_jmteb_tasks(task_types=["Classification"])

Mixed Precision

Use FP16/BF16 for faster evaluation:

import torch

model = JMTEBModel.from_sentence_transformer(
    "cl-nagoya/ruri-v3-30m",
    model_kwargs={"torch_dtype": torch.bfloat16}
)

Or via CLI:

python -m jmteb.v2 \
  --model_name cl-nagoya/ruri-v3-30m \
  --bf16 true \
  --save_path results_v2

Comparison with v1.x

Output Structure

results_v2/
└── model_name/
    ├── JSTS.json                    # Individual dataset results
    ├── JSICK.json
    ├── JaqketRetrieval.json
    ├── ...
    └── summary.json                 # Aggregated summary

Each dataset result file contains:

{
  "test": [
    {
      "main_score": 0.8214,
      "metric1": value1,
      "metric2": value2,
      ...
    }
  ]
}

Migration from v1.x

See MIGRATION_V2.md for a comprehensive migration guide.

Quick comparison:

v1.x:

from jmteb.embedders import SentenceBertEmbedder
embedder = SentenceBertEmbedder(model_name_or_path="cl-nagoya/ruri-base")
# ... manual evaluator setup

v2.0:

from jmteb.v2 import JMTEBModel, JMTEBV2Evaluator
from jmteb.v2.tasks import get_jmteb_tasks

model = JMTEBModel.from_sentence_transformer("cl-nagoya/ruri-v3-30m")
tasks = get_jmteb_tasks()
evaluator = JMTEBV2Evaluator(model=model, tasks=tasks)
evaluator.run()

Performance Tips

1. Use appropriate batch sizes: Larger models need smaller batches
2. Enable caching: Don't overwrite unless necessary
3. Use mixed precision: BF16 can significantly speed up evaluation
4. Filter datasets: Evaluate only what you need for faster iteration
5. Per-dataset batch sizes: Optimize for memory requirements

Examples

See the docs/examples/v2/ directory for complete examples:

• v2_basic_evaluation.py: Basic usage
• v2_cli_evaluation.sh: CLI examples
• v2_jmteb_lite.py: JMTEB-lite usage
• v2_mteb_model_loader.py: Using MTEB's model loader

For v1.x examples, see docs/examples/v1/.

Requirements

• Python >= 3.10
• PyTorch >= 2.0
• MTEB >= 1.22.0
• sentence-transformers >= 5.0
• Other dependencies in pyproject.toml

Citation

If you use JMTEB v2.0, please cite both JMTEB and MTEB:

@inproceedings{li2026jmteb,
    author = {Li, Shengzhe and Ohagi, Masaya and Ri, Ryokan and Fukuchi, Akihiko and Shibata, Tomohide and Kawahara, Daisuke},
    title = {{JMTEB and JMTEB-lite: Japanese Massive Text Embedding Benchmark and Its Lightweight Version}},
    booktitle = "Proceedings of the Fifteenth Language Resources and Evaluation Conference",
    month = may,
    year = "2026",
    address = "Palma, Mallorca, Spain",
    publisher = "European Language Resources Association",
    note = "to appear",
}

@article{muennighoff2022mteb,
  author = {Muennighoff, Niklas and Tazi, Nouamane and Magne, Loïc and Reimers, Nils},
  title = {MTEB: Massive Text Embedding Benchmark},
  publisher = {arXiv},
  journal={arXiv preprint arXiv:2210.07316},
  year = {2022}
  url = {https://arxiv.org/abs/2210.07316},
  doi = {10.48550/ARXIV.2210.07316},
}

License

Same as JMTEB v1.x. See LICENSE file.

Contributing

Contributions are welcome! Please:

1. Follow existing code style
2. Add tests for new features
3. Update documentation

Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions
• Documentation: See docs/ directory
• Migration Help: See docs/MIGRATION_V2.md

Acknowledgments

• MTEB team for the excellent evaluation framework
• All contributors to JMTEB v1.x
• Japanese NLP community for dataset contributions