This model implements QThink (Parallel Latent Reasoning via Per-Step Distillation of Multiple Rollouts) — an autoregressive latent reasoning loop that processes K=6 continuous thought steps before generating a text answer. Teacher hidden states are extracted from multiple chain-of-thought rollouts generated by the base model and distilled into the latent representations at every step.

Key idea: Instead of distilling from a single reasoning trace, we aggregate hidden states from multiple rollouts (16 per problem) and supervise every latent step. The teacher signal is the reward-weighted average of CORRECT rollouts only.

Architecture

Base model: Qwen3-1.7B (1.7B parameters)
Fine-tuning: LoRA (rank=32, alpha=16) on q/k/v/o/gate/up/down_proj
Projection head: Linear(2048, 2048) → GELU → Linear(2048, 2048) → LayerNorm(2048)
Latent steps: K=6 autoregressive continuous thought steps
Inference: Process prompt → K latent steps via ProjectionHead + KV cache → greedy text generation

Training Details

Parameter	Value
Mode	`codi_reward_weighted`
Per-step distillation	`False`
Distillation γ	1.0
Learning rate	0.0002
Epochs	3
Batch size (per GPU)	2
Gradient accumulation	8
Effective batch size	128 (across 8 GPUs)
Max answer length	128
Latent steps (K)	6
Task	GSM8k (7,473 training problems)
Rollouts per problem	16
GSM8k test accuracy	80.4%

How to Use

Requirements

pip install torch transformers

Inference Code

python

import torch
import torch.nn as nn
from transformers import AutoModelForCausalLM, AutoTokenizer

# Load model
model_name = "LakshyAAAgrawal/continuous-thought-r11_rw_finalstep_v1"
tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(
    model_name, torch_dtype=torch.bfloat16, device_map="auto"
)
model.eval()

# Load projection head
class ProjectionHead(nn.Module):
    def __init__(self, hidden_size):
        super().__init__()
        self.mlp = nn.Sequential(
            nn.Linear(hidden_size, hidden_size),
            nn.GELU(),
            nn.Linear(hidden_size, hidden_size),
            nn.LayerNorm(hidden_size),
        )
    def forward(self, x):
        return self.mlp(x)

proj = ProjectionHead(model.config.hidden_size)
proj.load_state_dict(torch.load(
    hf_hub_download(model_name, "projection_head.pt"), map_location="cpu"
))
proj = proj.to(model.dtype).to(model.device).eval()

# Generate with latent reasoning
question = "Natalia sold clips to 48 of her friends in April, and then she sold half as many clips in May. How many clips did Natalia sell altogether in April and May?"
messages = [{"role": "user", "content": f"Solve the following math problem step by step. Show your work and put your final numerical answer after ####.\n\n{question}"}]
prompt = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)

# Step 1: Process prompt
with torch.no_grad():
    out = model(**inputs, output_hidden_states=True, use_cache=True)
    past_kv = out.past_key_values
    latent = out.hidden_states[-1][:, -1, :]  # last token hidden state

    # Step 2: K latent reasoning steps
    mask = inputs["attention_mask"].clone()
    for k in range(6):
        latent = proj(latent)
        mask = torch.cat([mask, torch.ones(1, 1, device=mask.device, dtype=mask.dtype)], dim=1)
        out = model(inputs_embeds=latent.unsqueeze(1), attention_mask=mask,
                    past_key_values=past_kv, output_hidden_states=True, use_cache=True)
        past_kv = out.past_key_values
        latent = out.hidden_states[-1][:, -1, :]

    # Step 3: Greedy text generation
    next_token = out.logits[:, -1, :].argmax(dim=-1)
    generated = [next_token]
    for _ in range(2047):
        if next_token.item() == tokenizer.eos_token_id:
            break
        mask = torch.cat([mask, torch.ones(1, 1, device=mask.device, dtype=mask.dtype)], dim=1)
        out = model(input_ids=next_token.unsqueeze(0), attention_mask=mask,
                    past_key_values=past_kv, use_cache=True)
        past_kv = out.past_key_values
        next_token = out.logits[:, -1, :].argmax(dim=-1)
        generated.append(next_token)

    response = tokenizer.decode(torch.cat(generated), skip_special_tokens=True)
    print(response)

Evaluation

To evaluate on the full GSM8k test set, use the evaluation script from our repository:

bash

python evaluate.py \
    --model_dir LakshyAAAgrawal/continuous-thought-r11_rw_finalstep_v1 \
    --mode codi_reward_weighted \
    --output results/r11_rw_finalstep_v1.json \
    --max_new_tokens 2048 \
    --num_latent 6

Important: Use max_new_tokens=2048 for evaluation. The model generates verbose chain-of-thought text after the latent steps, requiring more tokens than standard models.

Results Comparison

Model	Mode	Per-step	γ	ans_len	GSM8k Accuracy
This model	codi_reward_weighted	False	1.0	128	80.4%
Qwen3-1.7B (base)	—	—	—	—	77.3%
Discrete SFT	sft	—	—	—	80.7%
QThink RW final-step	rw	no	1.0	128	81.0%
QThink Uniform per-step ans256	uniform	yes	2.0	256	83.2%
QThink RW per-step ans256	rw	yes	1.0	256	82.7%

Citation

If you use this model, please cite:

bibtex

@misc{continuous-thought-2025,
  title={QThink: Parallel Latent Reasoning via Per-Step Distillation of Multiple Rollouts},
  author={Lakshya Agrawal},
  year={2025},
  url={https://huggingface.co/LakshyAAAgrawal/continuous-thought-r11_rw_finalstep_v1}
}