mkd-hossain/keural-dpo-3500

Keural-DPO-14.83B (checkpoint 3500)

Keural is a bilingual Korean–English Mixture-of-Experts language model trained entirely from scratch. This is the DPO (Direct Preference Optimization) checkpoint at step 3,500 (~50% of 1 epoch), aligned from the Keural SFT-18k base using human preference data.

DPO alignment improves response quality, instruction-following, and reduces off-topic outputs compared to the SFT base.

Model Details

Property	Value
Architecture	Mixtral-style MoE (8 experts, top-2 routing)
Parameters	14.83B total / ~7.42B active per token
Layers	24
Hidden size	4096
Attention heads	32 (GQA — 8 KV heads)
Expert intermediate size	5632
Context length	4096 tokens
Vocabulary	131,074 (131,072 SPM + `<
RoPE theta	500,000
Sliding window	512 (alternating every other layer)
Dtype	bfloat16
Languages	Korean (primary), English

Full Training Pipeline

Stage	Steps	Tokens	Data
Pretraining Stage 1	100,000	~50B	Korean + English web corpus
Pretraining Stage 2	120,000	~13B	Korean + English web corpus (continued)
SFT	18,000	710M	mkd-chanwoo/keural-SFT (1.14M ChatML samples)
DPO (this checkpoint)	3,500 / 6,927	—	keural-dpo-raw (440K preference pairs)

DPO Hyperparameters

Hyperparameter	Value
Learning rate	2e-6 → 2e-7 cosine decay
Warmup steps	100
Beta (KL coefficient)	0.1
Effective batch size	64 (2 per GPU × 16 grad accum × 2 GPUs)
Max sequence length	1024 tokens
Optimizer	AdamW (β1=0.9, β2=0.95, ε=1e-8)
Weight decay	0.1
Max steps	6,927 (1 epoch over 440K pairs)
Hardware	2× NVIDIA H200 SXM (139 GiB each)
Parallelism	FSDP FULL_SHARD (ZeRO-3 equivalent)
Precision	bfloat16 + gradient checkpointing

SFT Hyperparameters (base checkpoint)

Hyperparameter	Value
Learning rate	1e-5 → 1e-6 cosine decay
Effective batch size	64 (4 per GPU × 8 grad accum × 2 GPUs)
Max sequence length	4096 tokens
Weight decay	0.05
Steps	18,000

Chat Format (ChatML)

This model uses ChatML format. You must use this exact format.

<|im_start|>system
You are a helpful bilingual Korean-English assistant.<|im_end|>
<|im_start|>user
안녕하세요! 오늘 날씨가 어때요?<|im_end|>
<|im_start|>assistant

The model generates until it produces <|im_end|> (token ID 131073).

Tip: Always include a system prompt. The model responds in the same language as the user when instructed to do so.

How to Use

With transformers

from transformers import AutoTokenizer, AutoModelForCausalLM
import torch

model_id = "mkd-hossain/keural-dpo-3500"

tokenizer = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForCausalLM.from_pretrained(
    model_id,
    torch_dtype=torch.bfloat16,
    device_map="auto",
)

messages = [
    {"role": "system", "content": "You are a helpful bilingual Korean-English assistant. Always respond in the same language as the user."},
    {"role": "user",   "content": "파이썬에서 리스트를 정렬하는 방법을 알려주세요."},
]

text = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(text, return_tensors="pt").to(model.device)

with torch.no_grad():
    output = model.generate(
        **inputs,
        max_new_tokens=512,
        temperature=0.7,
        top_p=0.9,
        repetition_penalty=1.1,
        no_repeat_ngram_size=8,
        do_sample=True,
        eos_token_id=131073,   # <|im_end|>
    )

response = tokenizer.decode(output[0][inputs.input_ids.shape[1]:], skip_special_tokens=False)
response = response.split("<|im_end|>")[0].strip()
print(response)

With vLLM (recommended for serving)

pip install vllm

python -m vllm.entrypoints.openai.api_server \
    --model mkd-hossain/keural-dpo-3500 \
    --tokenizer mkd-hossain/keural-dpo-3500 \
    --dtype bfloat16 \
    --max-model-len 4096 \
    --tensor-parallel-size 1

Then call the OpenAI-compatible endpoint:

from openai import OpenAI

client = OpenAI(base_url="http://localhost:8000/v1", api_key="none")

response = client.chat.completions.create(
    model="mkd-hossain/keural-dpo-3500",
    messages=[
        {"role": "system", "content": "You are a helpful bilingual assistant. Respond in the same language as the user."},
        {"role": "user",   "content": "한국의 수도는 어디인가요?"},
    ],
    max_tokens=512,
    temperature=0.7,
)
print(response.choices[0].message.content)

Multi-GPU serving

python -m vllm.entrypoints.openai.api_server \
    --model mkd-hossain/keural-dpo-3500 \
    --dtype bfloat16 \
    --max-model-len 4096 \
    --tensor-parallel-size 2

Manual ChatML prompt (without apply_chat_template)

prompt = (
    "<|im_start|>system\n"
    "You are a helpful bilingual Korean-English assistant. "
    "Always respond in the same language as the user.\n"
    "<|im_end|>\n"
    "<|im_start|>user\n"
    "Tell me about Seoul.<|im_end|>\n"
    "<|im_start|>assistant\n"
)

Special Tokens

Token	ID	Purpose
`<	im_start	>`
`<	im_end	>`
<bos>	1	Beginning of sequence
<eos>	2	End of sequence
<pad>	0	Padding

Important: Always set eos_token_id=131073 (<|im_end|>) when generating. Do not use eos_token_id=2.

Recommended Generation Settings

generation_config = {
    "max_new_tokens": 512,
    "temperature": 0.7,
    "top_p": 0.9,
    "top_k": 50,
    "repetition_penalty": 1.1,
    "no_repeat_ngram_size": 8,
    "do_sample": True,
    "eos_token_id": 131073,
}

For factual / deterministic tasks:

{"temperature": 0.1, "do_sample": False, "eos_token_id": 131073}

DPO Dataset

Training used the keural-dpo-raw dataset — 440,627 chosen/rejected preference pairs in ChatML format covering:

• General conversation (Korean and English)
• Question answering
• Instruction following
• Knowledge tasks

Limitations

• This is a mid-training checkpoint (step 3,500 of 6,927). A full-epoch checkpoint will be released when training completes.
• Maximum context is 4,096 tokens.
• The pretraining corpus is Korean-dominant. The model may default to Korean if no system prompt is provided.
• Always include a system prompt instructing the model to match the user's language for bilingual use.
• Not aligned for safety — do not deploy in production without additional safety fine-tuning.

License

Apache 2.0