---
license: apache-2.0
base_model: Qwen/Qwen2.5-Coder-1.5B-Instruct
tags:
  - code
  - c
  - linux-kernel
  - python
library_name: transformers
pipeline_tag: text-generation
---

# kernel-coder-1.5b

A 1.5B code model that writes **C in Linux kernel style** — tab indentation,
brace placement, declarations before statements, `-ERRNO` returns, `goto` label
unwinding — while keeping the base model's Python ability.

## Usage

```python
from transformers import AutoModelForCausalLM, AutoTokenizer

repo = "nethunter2023/kernel-coder-1.5b"
tok = AutoTokenizer.from_pretrained(repo)
model = AutoModelForCausalLM.from_pretrained(repo, dtype="bfloat16", device_map="auto")

messages = [
    {"role": "system", "content": "You are a Linux kernel developer. Reply with a "
                                  "single C code block containing only the function."},
    {"role": "user", "content": "Implement `int demo_probe(struct device *dev)`: "
                                "allocate a private struct and unwind on error."},
]
ids = tok.apply_chat_template(messages, add_generation_prompt=True, return_tensors="pt")
out = model.generate(ids.to(model.device), max_new_tokens=512, do_sample=False)
print(tok.decode(out[0][ids.shape[1]:], skip_special_tokens=True))
```

Chat template ships with the tokenizer. Greedy decoding; the answer is the last
fenced code block.

## Results — kernel C style

**N = 40** held-out kernel-doc tasks, greedy decoding, scored with the kernel's
own `scripts/checkpatch.pl --no-tree --file --strict`, reported as weighted
defects per line: `(2*errors + warnings + 0.5*checks) / lines`. All models were
given the identical prompts and scored by identical code.

| | params | defects / line ↓ | 95% CI | checkpatch errors ↓ | idiom ↑ |
|---|---|---|---|---|---|
| deepseek-coder-1.3b-instruct | 1.3B | 0.679 | ±0.196 | 4.43 | 0.738 |
| Qwen2.5-Coder-3B-Instruct | 3B | 0.750 | ±0.182 | 4.78 | 0.755 |
| Qwen2.5-Coder-1.5B-Instruct *(base)* | 1.5B | 0.872 | ±0.185 | 5.58 | 0.664 |
| **kernel-coder-1.5b** | **1.5B** | **0.020** | **±0.012** | **0.00** | **0.995** |
| *the kernel's own code* | — | *0.017* | — | *0.00* | *1.000* |

Against `Qwen2.5-Coder-3B-Instruct` — twice the parameters — the paired
difference is **−0.73 defects/line**, 95% CI [−0.91, −0.55], t = −7.87, lower on
**33 of 40** tasks. No general-purpose code model tested comes close, and this
model sits within noise of the kernel's own source.

## Results — Python

MBPP `test`, 200 problems, greedy, executing the dataset's assertions.

| | params | pass@1 |
|---|---|---|
| deepseek-coder-1.3b-instruct | 1.3B | 0.250 |
| **kernel-coder-1.5b** | 1.5B | **0.420** |
| Qwen2.5-Coder-1.5B-Instruct *(base)* | 1.5B | 0.420 |
| Qwen2.5-Coder-3B-Instruct | 3B | 0.535 |

Python is unchanged from base — the kernel specialisation cost nothing, and
gained nothing, here. A 3B model is still better at general Python.

If you re-run MBPP, strip the trailing `print(...)` / `assert` / `__main__`
statements the model appends after the function before executing. They run at
import time and abort otherwise-correct solutions; leaving them in costs roughly
3 points.

## Limitations

- **The kernel gains are stylistic and structural, not functional.** Kernel code
  cannot be executed in a sandbox, so nothing here measures semantic
  correctness. A well-formatted stub and a working implementation score alike.
  Review output before use.
- **A large share of the checkpatch improvement is indentation.** The base model
  indents kernel C with spaces; this one uses tabs, and checkpatch flags every
  space-indented line.
- **Roughly half of kernel completions** leave part of the body as placeholder
  comments rather than a full implementation — a rate unchanged from base.
- **N = 40** on the kernel evaluation. The margin over the baselines is large
  relative to that, but finer distinctions would need a bigger set.
- Training methodology is not published.

Base model: [`Qwen/Qwen2.5-Coder-1.5B-Instruct`](https://huggingface.co/Qwen/Qwen2.5-Coder-1.5B-Instruct)