app.py

import gradio as gr
import torch
import numpy as np
import json
import time
from transformers import AutoTokenizer
import os
import importlib
from huggingface_hub import hf_hub_download
from llama_diffusion_model import CustomTransformerModel, CustomTransformerConfig, BidirectionalLlamaAttention, disable_dropout
import spaces

hf_token = os.getenv("HF_TOKEN")


# --- Load tokenizer ---
tokenizer = AutoTokenizer.from_pretrained("meta-llama/Llama-3.2-3B", use_fast=True, token=hf_token)
vocab_size = len(tokenizer)
pad_token = tokenizer.pad_token_id or tokenizer.eos_token_id
eot_token_id = tokenizer.eos_token_id
assistant_marker_ids = tokenizer.encode("Assistant:", add_special_tokens=False)

# --- Load token probabilities ---
with open("token_probabilities.json") as f:
    token_probs_dict = json.load(f)
token_probabilities = np.array([token_probs_dict[str(i)] for i in range(len(token_probs_dict))], dtype=np.float32)

def load_model():
    ckpt_path = hf_hub_download(
        repo_id="ruurd/tini_model",
        filename="diffusion-model.pth",
        token=os.getenv("HF_TOKEN")
    )

    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    model = torch.load(ckpt_path, map_location=device)
    model = disable_dropout(model)
    model.to(device)
    model.eval()
    return model


rng = np.random.default_rng()

# --- Utility Functions ---
def decode_tokens_safe(token_ids):
    return tokenizer.decode(token_ids, skip_special_tokens=True).replace("\n", " ")

def find_answer_start(input_ids, marker_ids):
    for i in range(len(input_ids) - len(marker_ids) + 1):
        if input_ids[i:i + len(marker_ids)] == marker_ids:
            return i + len(marker_ids)
    return None

def get_noising_schedule(i, max_it, sharpness=5.0):
    x = i / max_it
    return (np.exp(-sharpness * x) - np.exp(-sharpness)) / (1 - np.exp(-sharpness))

def noisify_answer(input_ids, answer_start, threshold=1.0, eot_weight=1.0, clustering=0.5):
    noised = input_ids.copy()
    answer_len = len(noised) - answer_start
    num_to_noise = int(threshold * answer_len)

    if num_to_noise == 0:
        return noised, []

    mixed_probs = token_probabilities.copy()
    mixed_probs[eot_token_id] *= eot_weight
    mixed_probs /= mixed_probs.sum()

    num_clusters = max(1, int((1 - clustering) * num_to_noise))
    cluster_size = max(1, int(num_to_noise / num_clusters))

    noised_indices = set()
    for _ in range(num_clusters):
        center = rng.integers(answer_start, len(noised))
        span_start = max(answer_start, center - cluster_size // 2)
        span_end = min(len(noised), span_start + cluster_size)
        noised_indices.update(range(span_start, span_end))

    noised_indices = sorted(list(noised_indices))[:num_to_noise]

    noise = rng.choice(np.arange(vocab_size), size=len(noised_indices), p=mixed_probs)
    for idx, val in zip(noised_indices, noise):
        noised[idx] = val

    return noised, noised_indices


# Add new noising function
def confidence_guided_noising(input_ids, answer_start, confidences, threshold, eot_weight, noise_clipping):
    noised = input_ids.copy()
    answer_len = len(input_ids) - answer_start
    num_to_noise = int(threshold * answer_len)

    if num_to_noise == 0:
        return noised

    
    raw_weights = 1.0 - np.array(confidences[answer_start:])

    # Avoid zero-probability weights for selection
    # If noise clipping == 1, all tokens have equal chance to be noised. 
    # If noise_clipping == 0.00001, all tokens are noised according to the confidence of the past prediction
    raw_weights = np.clip(raw_weights, a_min = noise_clipping, a_max = None)

    weights = raw_weights / raw_weights.sum()

    if num_to_noise > len(weights):
        num_to_noise = len(weights)  # prevent oversampling

    indices = rng.choice(
        np.arange(answer_start, len(input_ids)),
        size=num_to_noise,
        replace=False,
        p=weights
    )

    mixed_probs = token_probabilities.copy()
    mixed_probs[eot_token_id] *= eot_weight
    mixed_probs /= mixed_probs.sum()

    noise = rng.choice(np.arange(vocab_size), size=num_to_noise, p=mixed_probs)
    for idx, val in zip(indices, noise):
        noised[idx] = val

    return noised




@spaces.GPU
def generate_diffusion_text(input_ids, answer_start):
    with torch.no_grad():
        input_tensor = torch.tensor([input_ids], dtype=torch.long).to(model.device)
        logits = model(input_ids=input_tensor)["logits"]
        probs = torch.nn.functional.softmax(logits, dim=-1).squeeze()
        probs = torch.clamp(probs, min=1e-8, max=1.0)
        sampled = torch.multinomial(probs, num_samples=1).squeeze().tolist()

        # Extract confidence of selected tokens
        conf = probs[range(len(sampled)), sampled].cpu().numpy()
    return sampled, conf 

# --- Inference Wrapper ---
def diffusion_chat(question, eot_weight, max_it, sharpness, noise_clipping, use_confidence_noising, clustering):
    placeholder = "What do you know about the city of New York?"
    if question.strip() == "":
        question = placeholder

    print('started generation')
    prompt = f"User: {question}\nAssistant:"
    input_ids = tokenizer.encode(prompt, add_special_tokens=False)
    answer_start = find_answer_start(input_ids, assistant_marker_ids)
    if answer_start is None:
        yield "Error: Could not find Assistant marker in input."
        return

    if len(input_ids) < 256:
        input_ids += [pad_token] * (256 - len(input_ids))
    else:
        input_ids = input_ids[:256]

    ori_input_tokens = input_ids
    current_tokens, just_noised_indices = noisify_answer(
        ori_input_tokens, answer_start, threshold=1.0, eot_weight=eot_weight, clustering=clustering
    )    
    last_tokens = []
    prev_decoded_tokens = []

    for i in range(max_it):
        print('Generating output')
        generated_tokens, confidences = generate_diffusion_text(current_tokens, answer_start)
        current_tokens = generated_tokens

        # --- Decode and highlight changed tokens in GREEN ---
        decoded_ids = current_tokens[answer_start:]
        decoded_tokens = tokenizer.convert_ids_to_tokens(decoded_ids)

        highlighted = []
        for j, tok in enumerate(decoded_tokens):
            token_str = tokenizer.convert_tokens_to_string([tok])
            if prev_decoded_tokens and j < len(prev_decoded_tokens) and tok != prev_decoded_tokens[j]:
                highlighted.append(f'<span style="color:green">{token_str}</span>')
            else:
                highlighted.append(token_str)

        prev_decoded_tokens = decoded_tokens
        yield f"<b>Iteration {i+1}/{max_it} (after generation):</b><br>" + "".join(highlighted).replace('\n', '<br>')
        time.sleep(0.1)

        # --- Apply noising and highlight RED tokens ---
        threshold = get_noising_schedule(i, max_it, sharpness=sharpness)
        if use_confidence_noising:
            current_tokens = confidence_guided_noising(
                generated_tokens, answer_start, confidences, threshold, eot_weight, noise_clipping
            )
            just_noised_indices = []  # Optional: could extract from confidence scores
        else:
            current_tokens, just_noised_indices = noisify_answer(
                generated_tokens, answer_start, threshold=threshold, eot_weight=eot_weight, clustering=clustering
            )

        decoded_ids = current_tokens[answer_start:]
        decoded_tokens = tokenizer.convert_ids_to_tokens(decoded_ids)

        highlighted = []
        for j, tok in enumerate(decoded_tokens):
            tok_id = tokenizer.convert_tokens_to_ids(tok)
            if tok_id == eot_token_id:
                continue  # Skip EOT tokens in display

            token_str = tokenizer.convert_tokens_to_string([tok])
            abs_idx = answer_start + j
            if abs_idx in just_noised_indices:
                highlighted.append(f'<span style="color:red">{token_str}</span>')
            else:
                highlighted.append(token_str)

        yield f"<b>Iteration {i+1}/{max_it} (after noising):</b><br>" + "".join(highlighted).replace('\n', '<br>')
        time.sleep(0.1)

        # --- Early stopping ---
        last_tokens.append(generated_tokens)
        if len(last_tokens) > 3:
            last_tokens.pop(0)
        if len(last_tokens) == 3 and last_tokens[0] == last_tokens[1] == last_tokens[2]:
            yield f"<b>Stopped early after {i+1} iterations.</b>"
            break



    final_tokens = tokenizer.convert_ids_to_tokens(current_tokens[answer_start:])
    final_tokens = [tok for tok in final_tokens if tokenizer.convert_tokens_to_ids(tok) != eot_token_id]
    final_output = tokenizer.convert_tokens_to_string(final_tokens)
    print(final_output)
    yield f"<b>Final Output (after {i+1} iterations):</b><br>" + final_output.replace('\n', '<br>')

# --- Gradio Interface ---
print("Loading model...")
model = load_model()
print("✅ Model loaded.")

demo = gr.Interface(
    fn=diffusion_chat,
    inputs=[
        gr.Textbox(label="User Question", lines=2, placeholder="What do you know about the city of New York?"),
        gr.Slider(0, 1, value=0.4, step=0.05, label="↓ = longer answers (EOT weight)"),
        gr.Slider(1, 512, value=64, step=1, label="↑ = more iterations"),
        gr.Slider(1.0, 20.0, value=5.0, step=0.5, label="↓ = more noising (sharpness)"),
        gr.Slider(0.01, 1.0, value=0.05, step=0.01, label="↓ = more confidence guidance (noise clipping)"),
        gr.Checkbox(value=False, label="Use confidence-guided noising"),
        gr.Slider(0.0, 1.0, value=0.5, step=0.05, label="↑ = more clustered noising (fewer, larger edits)")
    ],
    outputs=[gr.HTML(label="Diffusion Output")],
    title="Diffusion Language Model Chat",
    theme="default",
    description="This interface runs a diffusion-based language model to generate answers progressively."
)

demo.launch(share=True, allowed_paths=["."], ssr_mode=False)