shroom_classifier_v3_persona.py

# -*- coding: utf-8 -*-

from operator import itemgetter
from langchain.chat_models import ChatOpenAI
from langchain.prompts import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser

class ShroomClassifier:
    """Represents a classifier for the SHROOM evaluation dataset."""

    PERSONA = {
        "MT": "a translator concerned that the output is a good and accurate translation",
        "DM": "a lexicographer concerned that the output accurately captures the meaning of the word being defined",
        "TS": "an editor concerned that the output is short and simple",
        "PG": "an author concerned that the output is an accurate paraphrase that does not distort the meaning of the input",
    }

    TASK = {
        "DM": "The given task is Definition Modeling, meaning that the goal of the language model is to generate a definition for the term between the '<define>' and '</define>' delimiters in the input.",
        "PG": "The given task is Paraphrase Generation, meaning that the goal of the language model is to generate a paraphrase of the input.",
        "MT": "The given task is Machine Translation, meaning that the goal of the language model is to generate a natural language translation of the input.",
        "TS": "The given task is Text Simplification, meaning that the goal of the language model is to generate a simplified version of the input.",
    }

    RATIONALE_GENERATION_PROMPT = """A language model has generated an output from a given input for a specific task.
{task} You are {persona}. You will be given three inputs: input text, target text, and generated text.
You are asked to evaluate the generated text looking at the input text and the target text. Then, you need to decide whether the generated text is a hallucination or not.
There are two criteria for hallucination:
- If the generated text contains any nonsensical or factually incorrect information, it is a hallucination.
- If the generated text contains additional information that cannot be supported by the input text or the target text, it is a hallucination.
- Else, the generated text is not a hallucination.
Now, it is time to look at the inputs.
Input text: {src}
Target text: {tgt}
Generated text: {hyp}
Is the generated text a hallucination? Provide a short rationale for your answer.
Rationale:
"""

    ANSWER_GENERATION_PROMPT = """Using the argument provided in the below rationale, answer the question: 
is the output a hallucination? Answer 'Hallucination' if the output is a hallucination, or 'Not Hallucination' 
if it is not a hallucination. Only answer 'Hallucination' or 'Not Hallucination'.
  
Input: {src}
Target: {tgt} 
Output: {hyp}
Rationale: {rationale}
Answer:
"""
    
    def __init__(self, model_name="gpt-4", temperature=0.1):
        """
        Initializes a classifier for the SemEval 2024 Task 6.
        
        Parameters:
            model_name: The name of the model to be used for zero shot CoT classification (default "gpt-4").
            temperature: The temperature parameter for the model (default 0.1).
         """
        self.model_name = model_name
        self.temperature = temperature
        self.llm = self._llm(model_name, temperature)
        self.chain = self._zero_shot_chain_of_thought()

    def _llm(self, model_name, temperature):
        if model_name in [
            "gpt-4",
            "gpt-3.5-turbo",
            "gpt-4-1106-preview",
            ]:
            return ChatOpenAI(model_name=model_name, temperature=temperature, request_timeout=100)
        else:
            raise Exception(f'Model {model_name} not supported')

    def _zero_shot_chain_of_thought(self):
        """
        Creates a  LCEL chain that implements a zero-shot
        chain of thought (CoT) using a specification. 
        """
        rationale_generation = (
            ChatPromptTemplate.from_template(self.RATIONALE_GENERATION_PROMPT) 
            | self.llm 
            | StrOutputParser()
        )
        answer_generation = (
             { 
                "rationale": rationale_generation, 
                "hyp": itemgetter("hyp"),
                "src": itemgetter("src"),
                "tgt": itemgetter("tgt"),
             }
             | ChatPromptTemplate.from_template(self.ANSWER_GENERATION_PROMPT)
             | self.llm
             | StrOutputParser()
        )
        return answer_generation
    
    def classify(self, dp):
        """
        Determines whether or not the output (hyp) is a hallucination.
        
        Parameters:
            task: The task associated with a datapoint. One of "DM", "PG", "MT", or "TS".
            src: The input passed to a model.
            tgt: The intended reference "gold" text that the model ought to generate
            hyp: The output the model generated.
        
        Returns:
            A dict containing a classification of the output based on the task, input, output and target.
        """
        predictions = self.chain.batch([ 
            { 
                "task": self.TASK[dp["task"]], 
                "persona": self.PERSONA[dp["task"]], 
                "src": dp["src"], 
                "tgt": dp["tgt"], 
                "hyp": dp["hyp"] 
            } for i in range(5) ])
        weight = 1./float(len(predictions))
        predicted_p = float(sum([ weight for prediction in predictions if prediction == 'Hallucination' ]))
        if predicted_p > 0.5:
            predicted = "Hallucination"
        else:
            predicted = "Not Hallucination"
        if "id" in dp:
            return { "id": dp["id"], "label": predicted, "p(Hallucination)": predicted_p }
        else:
            return { "label": predicted, "p(Hallucination)": predicted_p }