---
license: apache-2.0
language:
- en
library_name: transformers
pipeline_tag: text-generation
base_model:
- codelion/dhara-250m-ar-base
datasets:
- codelion/sutra-10B
- HuggingFaceFW/fineweb-edu
- allenai/tulu-3-sft-mixture
- NousResearch/hermes-function-calling-v1
tags:
- diffusion-llm
- block-diffusion
- autoregressive
- self-speculation
- tri-mode
model-index:
- name: dhara-250m
  results:
  - task:
      type: text-generation
    dataset:
      name: PIQA
      type: piqa
    metrics:
    - name: Accuracy
      type: acc_norm
      value: 58.3
  - task:
      type: text-generation
    dataset:
      name: WinoGrande
      type: winogrande
    metrics:
    - name: Accuracy
      type: acc
      value: 51.9
  - task:
      type: text-generation
    dataset:
      name: TruthfulQA MC2
      type: truthfulqa_mc2
    metrics:
    - name: Accuracy
      type: mc2
      value: 43.3
  - task:
      type: text-generation
    dataset:
      name: BoolQ
      type: boolq
    metrics:
    - name: Accuracy
      type: acc
      value: 51.2
  - task:
      type: text-generation
    dataset:
      name: OpenBookQA
      type: openbookqa
    metrics:
    - name: Accuracy
      type: acc_norm
      value: 31.2
  - task:
      type: text-generation
    dataset:
      name: ARC-Easy
      type: arc_easy
    metrics:
    - name: Accuracy
      type: acc_norm
      value: 40.7
  - task:
      type: text-generation
    dataset:
      name: HellaSwag
      type: hellaswag
    metrics:
    - name: Accuracy
      type: acc_norm
      value: 38.3
  - task:
      type: text-generation
    dataset:
      name: ARC-Challenge
      type: arc_challenge
    metrics:
    - name: Accuracy
      type: acc_norm
      value: 24.7
  - task:
      type: text-generation
    dataset:
      name: MMLU (5-shot)
      type: mmlu
    metrics:
    - name: Accuracy
      type: acc
      value: 25.8
  - task:
      type: text-generation
    dataset:
      name: SciQ
      type: sciq
    metrics:
    - name: Accuracy
      type: acc
      value: 61.3
  - task:
      type: text-generation
    dataset:
      name: Average (10 tasks)
      type: average
    metrics:
    - name: Accuracy
      type: acc
      value: 42.7
---

# Dhara-250M — Tri-Mode (AR + Block-Diffusion + Self-Speculation)

A **250M-parameter** language model that decodes in **three modes from one set of weights**, following NVIDIA's [*Nemotron-Labs-Diffusion: Tri-Mode*](https://huggingface.co/blog/nvidia/nemotron-labs-diffusion) recipe (joint AR + block-diffusion training). Built from `codelion/dhara-250m-ar-base` and trained to **~60B cumulative tokens** (~50B added for this model). Architecture: LLaMA-style with Canon depthwise-conv layers, QK-norm, logit soft-cap, GQA, RoPE θ=8M.

**Demo:** [dhara-chat Space](https://huggingface.co/spaces/codelion/dhara-chat) — chat with it and compare all three decoding modes.

## The three modes

| Mode | How | Use it for |
|---|---|---|
| **AR** | causal mask, KV-cached `generate()` | highest-quality left-to-right generation |
| **Block-diffusion** | block-causal mask, parallel unmasking | lower-latency parallel decoding (quality tradeoff) |
| **Self-speculation** | diffusion drafts → AR verifies | **AR-quality** output at lower latency (lossless-ish) |

## Usage (transformers — works directly, no extra files)

```python
import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

ck = "codelion/dhara-250m"
tok = AutoTokenizer.from_pretrained(ck, trust_remote_code=True)
model = AutoModelForCausalLM.from_pretrained(ck, trust_remote_code=True, torch_dtype=torch.bfloat16).cuda().eval()
im_end = tok.convert_tokens_to_ids("<|im_end|>")

msgs = [{"role": "user", "content": "Give me three tips for staying healthy."}]
prompt = tok.apply_chat_template(msgs, tokenize=False, add_generation_prompt=True)
ids = tok(prompt, return_tensors="pt", add_special_tokens=False).input_ids.cuda()

# Mode 1 — AR (recommended for chat); sampling gives the best quality
out = model.generate(ids, max_new_tokens=128, do_sample=True, temperature=0.7,
                     top_p=0.9, repetition_penalty=1.15, eos_token_id=im_end)
print(tok.decode(out[0, ids.shape[1]:], skip_special_tokens=True))

# Mode 2 — block-diffusion (faster, quality tradeoff)
print(tok.decode(model.generate_diffusion(ids, block_len=32, threshold=0.5, max_new_tokens=128)[0, ids.shape[1]:], skip_special_tokens=True))

# Mode 3 — self-speculation (AR-quality, speedup)
print(tok.decode(model.generate_self_spec(ids, k=8, max_new_tokens=128)[0, ids.shape[1]:], skip_special_tokens=True))
```

Chat template is **ChatML + Hermes-style tools** (shipped in the tokenizer); the model supports an OpenAI-style `tools=[...]` argument.

## Benchmarks (lm-eval-harness 0.4.11, identical harness for all models)

10 tasks (9 zero-shot + MMLU 5-shot); metric = `acc_norm` where defined, else `acc`. Columns: **dhara-base** (the AR base, [codelion/dhara-250m-ar-base](https://huggingface.co/codelion/dhara-250m-ar-base)), this model in **AR** mode and in **diffusion** mode (**dhara-diff**), and — as an external reference run through the *same* harness — **SmolLM-135M**.

| Task | dhara-base (AR) | dhara (AR) | dhara-diff | SmolLM-135M |
|---|--:|--:|--:|--:|
| piqa | 57.7 | 62.6 | 58.3 | 68.3 |
| winogrande | 50.1 | 50.0 | 51.9 | 53.1 |
| truthfulqa_mc2 | 50.1 | 46.4 | 43.3 | 39.3 |
| boolq | 37.8 | 37.8 | 51.2 | 59.9 |
| openbookqa | 32.2 | 32.4 | 31.2 | 33.8 |
| arc_easy | 30.2 | 32.4 | 40.7 | 56.2 |
| hellaswag | 27.2 | 33.5 | 38.3 | 42.7 |
| arc_challenge | 25.6 | 27.5 | 24.7 | 28.8 |
| mmlu (5-shot) | 22.9 | 22.9 | 25.8 | 25.9 |
| sciq | 21.3 | 23.3 | 61.3 | 74.7 |
| **Average** | **35.5** | **36.9** | **42.7** | **48.3** |

**Tri-mode training improves the AR base by +1.4 points (AR mode) and by +7.2 points in diffusion mode.** dhara-diff (42.7) is the headline configuration — bidirectional answer scoring drives large gains over the base on sciq (+40), boolq (+13) and arc_easy (+11).

**Data efficiency.** SmolLM-135M (48.3) was trained on **~600B tokens — roughly 10× dhara's ~60B** (built on the 10B-token pedagogical [sutra-10B](https://huggingface.co/datasets/codelion/sutra-10B) corpus). Despite that 10× data gap, **dhara-diff lands only ~12% below SmolLM-135M on average** (42.7 vs 48.3) and wins truthfulqa outright — echoing the data-efficiency results in [*Scaling Pedagogical Pre-training to 10 Billion Tokens*](https://huggingface.co/blog/codelion/scaling-pedagogical-pretraining-10-billion-tokens).

## Decoding speed (single H100, measured)

| Mode | batch-1 latency | peak batched throughput | quality |
|---|--:|--:|---|
| **AR** (KV-cached) | 61 tok/s | **33,067 tok/s** (batch 4096) | full |
| **Block-diffusion** (thr 0.5) | **103 tok/s** | ~2,200 tok/s (OOM ≥ batch 2048) | quality tradeoff |
| **Self-speculation** (k=8) | 84 tok/s | ~2,200 tok/s | AR-quality (accept ~1.4/8) |

Two regimes. **At batch 1, block-diffusion and self-speculation are 1.4–1.7× faster than AR** — they emit 2.09 / 1.20 tokens per model forward, a single-stream latency win. **Batched for throughput, AR wins by ~15×**: it is KV-cached (one new token per forward, scaling 61 → 33,067 tok/s from batch 1 → 4096), whereas the diffusion modes re-run a full *uncached* forward over the whole block each step and saturate memory early. Rule of thumb: reach for diffusion/self-speculation for **low-latency single-stream** decoding, and for **batched AR** when you want maximum throughput.

## Context length

**4k tokens.** Config permits 32768 (θ=8M) and the architecture includes YaRN, but the model was only trained to 4k; perplexity is flat to ~4k, mild at 8k, and degrades sharply beyond (16k–32k).

## Training

`codelion/dhara-250m-ar-base` → +30B continued pretraining + 10B high-LR probe on the pedagogical [sutra-10B](https://huggingface.co/datasets/codelion/sutra-10B) corpus → **+7B Stage-2 joint AR+block-diffusion** (α=0.3, block 32) → **+2B joint SFT** (Tulu-3 + Hermes function-calling) → **+1B annealing** (FineWeb-Edu + chat) ≈ **60B cumulative tokens**.

## Serving

Please use Hugging Face **`transformers`** for serving (`from_pretrained(trust_remote_code=True)`) — all three modes work directly, with no extra files or setup.

## Example

Recommended chat settings (AR mode): `do_sample=True, temperature=0.7, top_p=0.9, repetition_penalty=1.15`.

**Prompt:** *Give me three tips for staying healthy.*

**Output:**

> Firstly, make sure you're eating plenty of fruits and vegetables. These are good sources of vitamins and minerals that help support your immune system and overall health. Additionally, stay hydrated by drinking plenty of water throughout the day. This will help regulate your body's temperature and keep you hydrated.

## References

- Recipe: [Nemotron-Labs-Diffusion: a Tri-Mode Language Model](https://huggingface.co/blog/nvidia/nemotron-labs-diffusion) (NVIDIA, 2026).
- Pedagogical pre-training: [Scaling Pedagogical Pre-training to 10 Billion Tokens](https://huggingface.co/blog/codelion/scaling-pedagogical-pretraining-10-billion-tokens).
- Pre-training data: [codelion/sutra-10B](https://huggingface.co/datasets/codelion/sutra-10B).