---
language:
- en
- zh
library_name: transformers
pipeline_tag: text-generation
tags:
- pretraining
- language-ordering
- curriculum
- bilingual
- smollm2
license: other
---

# pathlang-1p7b-runC-5050

A 1.7B-parameter bilingual (English + Chinese) language model, part of a **controlled
language-ordering study**. Three models share the *same* architecture, initialization, total data
diet (50B English + 50B Chinese = 100B tokens), and LR schedule; they differ **only** in the order
in which the two languages are presented during pretraining. This is the **balanced 50/50 control** run.

## Curriculum (this run)

- All phases: 50% English / 50% Chinese

The other runs in the study: `Raghav-Singhal/pathlang-1p7b-runA-zh-first`,
`Raghav-Singhal/pathlang-1p7b-runB-en-first`, `Raghav-Singhal/pathlang-1p7b-runC-5050`.

## Architecture

- SmolLM2-1.7B backbone: 24 layers, hidden size 2048, FFN 8192, 32 attention heads
- RoPE (base 10000), RMSNorm, SwiGLU, no biases, sequence length 2048
- **Tokenizer: Qwen3** (multilingual, vocab 151,936)
- ~2.1B total parameters (with the Qwen3 embedding)

## Training

- 100B tokens: 50B English (DCLM-edu) + 50B Chinese (FineWeb-2 `cmn_Hani`)
- Global batch size 960, sequence length 2048, 50,860 steps
- WSD LR schedule (peak 2e-4, 2000 warmup, linear decay over the final 10B tokens), bf16, Adam
- Converted from Megatron-LM to HF `LlamaForCausalLM` format

## Held-out validation loss (final checkpoint, 100B tokens)

| | English val | Chinese val |
|---|---|---|
| this run (balanced 50/50 control) | 2.648 | 2.480 |

Cross-entropy in nats/token on held-out blocks of the training corpora. The headline finding of the
study: each run ends **best at the language that dominated its middle (bulk) phase** — a recency
effect that also holds on an out-of-distribution corpus (HPLT4.0).

## Usage

```python
from transformers import AutoModelForCausalLM, AutoTokenizer
m = AutoModelForCausalLM.from_pretrained("Raghav-Singhal/pathlang-1p7b-runC-5050")
tok = AutoTokenizer.from_pretrained("Raghav-Singhal/pathlang-1p7b-runC-5050")
```

## Note

License is set to `other` pending confirmation; the training data (DCLM-edu, FineWeb-2) and their
respective terms apply. This is a base (non-instruction-tuned) research checkpoint.