model.py

import math
import os
from time import sleep, time

import spaces
import torch
from ibm_watsonx_ai.client import APIClient
from ibm_watsonx_ai.foundation_models import ModelInference
from transformers import AutoTokenizer
from vllm import LLM, SamplingParams

from logger import logger

safe_token = "No"
risky_token = "Yes"
nlogprobs = 5

inference_engine = os.getenv("INFERENCE_ENGINE", "VLLM")
logger.debug(f"Inference engine is: '{inference_engine}'")

if inference_engine == "VLLM":

    model_path = os.getenv("MODEL_PATH", "ibm-granite/granite-guardian-3.0-8b")
    logger.debug(f"model_path is {model_path}")
    tokenizer = AutoTokenizer.from_pretrained(model_path)
    sampling_params = SamplingParams(temperature=0.0, logprobs=nlogprobs)
    model = LLM(model=model_path, tensor_parallel_size=1)

elif inference_engine == "WATSONX":
    client = APIClient(
        credentials={"api_key": os.getenv("WATSONX_API_KEY"), "url": "https://us-south.ml.cloud.ibm.com"}
    )

    client.set.default_project(os.getenv("WATSONX_PROJECT_ID"))
    hf_model_path = "ibm-granite/granite-guardian-3.0-8b"
    tokenizer = AutoTokenizer.from_pretrained(hf_model_path)

    model_id = "ibm/granite-guardian-3-8b"  # 8B Model: "ibm/granite-guardian-3-8b"
    model = ModelInference(model_id=model_id, api_client=client)


def parse_output(output):
    label, prob = None, None

    if nlogprobs > 0:
        logprobs = next(iter(output.outputs)).logprobs
        if logprobs is not None:
            prob = get_probablities(logprobs)
            prob_of_risk = prob[1]

    res = next(iter(output.outputs)).text.strip()
    if risky_token.lower() == res.lower():
        label = risky_token
    elif safe_token.lower() == res.lower():
        label = safe_token
    else:
        label = "Failed"

    return label, prob_of_risk.item()


def softmax(values):
    exp_values = [math.exp(v) for v in values]
    total = sum(exp_values)
    return [v / total for v in exp_values]


def get_probablities(logprobs):
    safe_token_prob = 1e-50
    unsafe_token_prob = 1e-50
    for gen_token_i in logprobs:
        for token_prob in gen_token_i.values():
            decoded_token = token_prob.decoded_token
            if decoded_token.strip().lower() == safe_token.lower():
                safe_token_prob += math.exp(token_prob.logprob)
            if decoded_token.strip().lower() == risky_token.lower():
                unsafe_token_prob += math.exp(token_prob.logprob)

    probabilities = torch.softmax(torch.tensor([math.log(safe_token_prob), math.log(unsafe_token_prob)]), dim=0)

    return probabilities


def get_probablities_watsonx(top_tokens_list):
    safe_token_prob = 1e-50
    risky_token_prob = 1e-50
    for top_tokens in top_tokens_list:
        for token in top_tokens:
            if token["text"].strip().lower() == safe_token.lower():
                safe_token_prob += math.exp(token["logprob"])
            if token["text"].strip().lower() == risky_token.lower():
                risky_token_prob += math.exp(token["logprob"])

    probabilities = softmax([math.log(safe_token_prob), math.log(risky_token_prob)])

    return probabilities


def get_prompt(messages, criteria_name):
    guardian_config = {"risk_name": criteria_name if criteria_name != "general_harm" else "harm"}
    return tokenizer.apply_chat_template(
        messages, guardian_config=guardian_config, tokenize=False, add_generation_prompt=True
    )


def generate_tokens(prompt):
    result = model.generate(
        prompt=[prompt],
        params={
            "decoding_method": "greedy",
            "max_new_tokens": 20,
            "temperature": 0,
            "return_options": {"token_logprobs": True, "generated_tokens": True, "input_text": True, "top_n_tokens": 5},
        },
    )
    return result[0]["results"][0]["generated_tokens"]


def parse_output_watsonx(generated_tokens_list):
    label, prob_of_risk = None, None

    if nlogprobs > 0:
        top_tokens_list = [generated_tokens["top_tokens"] for generated_tokens in generated_tokens_list]
        prob = get_probablities_watsonx(top_tokens_list)
        prob_of_risk = prob[1]

    res = next(iter(generated_tokens_list))["text"].strip()

    if risky_token.lower() == res.lower():
        label = risky_token
    elif safe_token.lower() == res.lower():
        label = safe_token
    else:
        label = "Failed"

    return label, prob_of_risk


@spaces.GPU
def generate_text(messages, criteria_name):
    logger.debug(f"Messages used to create the prompt are: \n{messages}")

    start = time()

    chat = get_prompt(messages, criteria_name)
    logger.debug(f"Prompt is \n{chat}")

    if inference_engine == "MOCK":
        logger.debug("Returning mocked model result.")
        sleep(1)
        label, prob_of_risk = "Yes", 0.97

    elif inference_engine == "WATSONX":
        generated_tokens = generate_tokens(chat)
        label, prob_of_risk = parse_output_watsonx(generated_tokens)

    elif inference_engine == "VLLM":
        with torch.no_grad():
            output = model.generate(chat, sampling_params, use_tqdm=False)

        label, prob_of_risk = parse_output(output[0])
    else:
        raise Exception("Environment variable 'INFERENCE_ENGINE' must be one of [WATSONX, MOCK, VLLM]")

    logger.debug(f"Model generated label: \n{label}")
    logger.debug(f"Model prob_of_risk: \n{prob_of_risk}")

    end = time()
    total = end - start
    logger.debug(f"The evaluation took {total} secs")

    return {"assessment": label, "certainty": prob_of_risk}