app.py

import gradio as gr
import torch
import spaces
from transformers import AutoModelForCausalLM, AutoTokenizer
from peft import PeftModel

BASE = "Qwen/Qwen2.5-Math-7B"
ADAPTER = "billwang37/WWang-Lab-OptimAI"

print("Loading base model...")
base = AutoModelForCausalLM.from_pretrained(
    BASE, torch_dtype=torch.bfloat16, trust_remote_code=True
)
print("Applying LoRA adapter...")
model = PeftModel.from_pretrained(base, ADAPTER)
model.eval()

tokenizer = AutoTokenizer.from_pretrained(ADAPTER, trust_remote_code=True)
if tokenizer.pad_token is None:
    tokenizer.pad_token = tokenizer.eos_token


@spaces.GPU(duration=120)
def solve(prompt, max_new_tokens=1024):
    if not prompt.strip():
        return "Please enter an optimization problem."
    model.to("cuda")
    inputs = tokenizer(prompt, return_tensors="pt", truncation=True, max_length=2048).to("cuda")
    with torch.no_grad():
        out = model.generate(
            **inputs,
            max_new_tokens=int(max_new_tokens),
            do_sample=False,
            pad_token_id=tokenizer.pad_token_id,
        )
    full = tokenizer.decode(out[0], skip_special_tokens=True)
    prompt_text = tokenizer.decode(inputs.input_ids[0], skip_special_tokens=True)
    return full[len(prompt_text):].strip()


examples = [
    ["A factory produces A and B. A needs 2h labor, 3 units material, profit $5. B needs 1h labor, 2 units material, profit $4. Available: 100h labor, 200 units material. Maximize profit. Give the optimal x_A, x_B, and total profit.", 1024],
    ["Shortest path from A to D in graph: A-B (cost 3), A-C (cost 1), B-D (cost 2), C-D (cost 5), B-C (cost 1). Find the cost and path.", 512],
    ["When would you use Lagrangian relaxation instead of Benders decomposition?", 1024],
    ["Integer program: max 5x+4y s.t. 6x+4y<=24, x+2y<=6, x,y in {0,1,2,3,4,5,6}. Find optimal integer solution.", 1024],
]

with gr.Blocks(title="OptimAI Demo") as demo:
    gr.Markdown("# OptimAI: Operations Research Assistant")
    gr.Markdown(
        "A Qwen2.5-Math-7B fine-tune (SFT + DPO) for OR problems: LP, IP, "
        "shortest path, queueing, KKT, duality, etc. Try an example or paste your own."
    )
    with gr.Row():
        with gr.Column(scale=2):
            prompt = gr.Textbox(label="Problem", lines=8, placeholder="Maximize 3x + 5y subject to ...")
            tokens = gr.Slider(128, 2048, value=1024, step=64, label="Max new tokens")
            btn = gr.Button("Solve", variant="primary")
        with gr.Column(scale=3):
            output = gr.Textbox(label="Model output", lines=20)

    btn.click(solve, inputs=[prompt, tokens], outputs=output)
    gr.Examples(examples=examples, inputs=[prompt, tokens])

    gr.Markdown(
        "**Model:** [billwang37/WWang-Lab-OptimAI](https://huggingface.co/billwang37/WWang-Lab-OptimAI)  \n"
        "**Note:** First call takes ~30-60s (cold start). Subsequent calls ~10-20s."
    )


if __name__ == "__main__":
    demo.launch()