Custom LLM as a Judge to Detect Hallucinations with Braintrust

%pip install autoevals duckdb braintrust openai --quiet

import duckdb

# DuckDB has an easy wrapper for loading datasets from Hugging Face.
con = duckdb.connect(":memory:")
full_result = con.query("""
    SELECT * FROM 'hf://datasets/stanfordnlp/coqa/data/validation-00000-of-00001.parquet'
        LIMIT 40
""").fetchall()

single_result = full_result[10]

print("Passage:")
print(single_result[1])

print("\nQuestion:")
print(single_result[2][0])

print("\nAnswer:")
print(single_result[3]["input_text"][0])

from dataclasses import dataclass


@dataclass
class QuestionAnswer:
    passage: str
    question: str
    expected_answer: str
    generated_answer: str


qa_pairs = [
    QuestionAnswer(
        passage=r[1],
        question=question,
        generated_answer=r[3]["input_text"][i],
        expected_answer=r[3]["input_text"][i],
    )
    for r in full_result
    for (i, question) in enumerate(r[2])
]

print(len(qa_pairs))

import asyncio
import random

random.seed(42)


async def hallucinate_answer(qa):
    response = await client.chat.completions.create(
        model="gpt-4o",
        messages=[
            {
                "role": "system",
                "content": """\
You are a helpful hallucinating assistant, who makes up fake answers to questions.

Answer the following question in 1 sentence. If you know the answer, then make up some fake
superfluous details that are not in the passage you have memorized.

Make sure to always answer it confidently, even if you don't know the answer. Do not use words
like "perhaps", "likely", "maybe", etc. or punctuation like "...".Do not admit that you cannot
or do not know the answer.""",
            },
            {"role": "user", "content": qa.question},
        ],
        temperature=1,
        max_tokens=100,
    )
    return response.choices[0].message.content


hallucinated_answers = await asyncio.gather(
    *[hallucinate_answer(qa) for qa in qa_pairs]
)


hallucinations = [
    QuestionAnswer(
        passage=qa.passage,
        question=qa.question,
        expected_answer=qa.expected_answer,
        generated_answer=hallucination,
    )
    for (qa, hallucination) in zip(qa_pairs, hallucinated_answers)
    # Exclude simple yes/no answers.
    if "yes" not in hallucination.lower() and "no" not in hallucination.lower()
]

print("Passage:")
print(hallucinations[0].passage)
print("\nQuestion:")
print(hallucinations[0].question)
print("\nExpected Answer:")
print(hallucinations[0].expected_answer)
print("\nGenerated Answer:")
print(hallucinations[0].generated_answer)

print("\n\nNumber of hallucinations:", len(hallucinations))

import json

PROMPT = """\
You are comparing a submitted answer to an expert answer on a given question. Here is the data:
[BEGIN DATA]
************
[Question]: {input}
************
[Expert]: {expected}
************
[Submission]: {output}
************
[END DATA]

Compare the factual content of the submitted answer with the expert answer. Ignore any differences in style, grammar, or punctuation.
Rate the submission on a scale of 1 to 10.
"""


@braintrust.traced
async def numeric_rater(input, output, expected):
    response = await client.chat.completions.create(
        model="gpt-4o",
        messages=[
            {
                "role": "user",
                "content": PROMPT.format(input=input, output=output, expected=expected),
            }
        ],
        temperature=0,
        tools=[
            {
                "type": "function",
                "function": {
                    "name": "rate",
                    "description": "Rate the submission on a scale of 1 to 10.",
                    "parameters": {
                        "type": "object",
                        "properties": {
                            "rating": {"type": "integer", "minimum": 1, "maximum": 10},
                        },
                        "required": ["rating"],
                    },
                },
            }
        ],
        tool_choice={"type": "function", "function": {"name": "rate"}},
    )
    arguments = json.loads(response.choices[0].message.tool_calls[0].function.arguments)
    return (arguments["rating"] - 1) / 9


print(qa_pairs[10].question, "On a correct answer:", qa_pairs[10].generated_answer)
print(
    await numeric_rater(
        qa_pairs[10].question,
        qa_pairs[10].generated_answer,
        qa_pairs[10].expected_answer,
    )
)

print(
    hallucinations[10].question,
    "On a hallucinated answer:",
    hallucinations[10].generated_answer,
)
print(
    await numeric_rater(
        hallucinations[10].question,
        hallucinations[10].generated_answer,
        hallucinations[10].expected_answer,
    )
)

from dataclasses import asdict

from braintrust import Eval


def data():
    for pair in hallucinations:
        yield dict(
            input=dict(asdict(pair)), expected=0, metadata=dict(hallucination=True)
        )


async def task(input):
    return await numeric_rater(
        input=input["question"],
        output=input["generated_answer"],
        expected=input["expected_answer"],
    )


def normalized_diff(output, expected):
    return 1 - abs(output - expected)


await Eval(
    "LLM-as-a-judge",
    data=data,
    task=task,
    scores=[normalized_diff],
    experiment_name="Numeric rater",
    max_concurrency=10,
)

@braintrust.traced
async def numeric_rater(input, output, expected):
    response = await client.chat.completions.create(
        model="gpt-4o",
        messages=[
            {
                "role": "user",
                "content": PROMPT.format(input=input, output=output, expected=expected),
            }
        ],
        temperature=0,
        tools=[
            {
                "type": "function",
                "function": {
                    "name": "rate",
                    "description": "Rate the submission on a scale of 1 to 10.",
                    "parameters": {
                        "type": "object",
                        "properties": {
                            "reasons": {
                                "description": "Write out in a step by step manner your reasoning to be sure that your conclusion is correct. Avoid simply stating the correct answer at the outset.",
                                "title": "Reasoning",
                                "type": "string",
                            },
                            "rating": {"type": "integer", "minimum": 1, "maximum": 10},
                        },
                        "required": ["rating"],
                    },
                },
            }
        ],
        tool_choice={"type": "function", "function": {"name": "rate"}},
    )
    arguments = json.loads(response.choices[0].message.tool_calls[0].function.arguments)
    return (arguments["rating"] - 1) / 9


print(qa_pairs[10].question, "On a correct answer:", qa_pairs[10].generated_answer)
print(
    await numeric_rater(
        qa_pairs[10].question,
        qa_pairs[10].generated_answer,
        qa_pairs[10].expected_answer,
    )
)

print(
    hallucinations[10].question,
    "On a hallucinated answer:",
    hallucinations[10].generated_answer,
)
print(
    await numeric_rater(
        hallucinations[10].question,
        hallucinations[10].generated_answer,
        hallucinations[10].expected_answer,
    )
)

await Eval(
    "LLM-as-a-judge",
    data=data,
    task=task,
    scores=[normalized_diff],
    experiment_name="Numeric rater with reasoning",
    max_concurrency=10,
)

PROMPT = """\
You are comparing a submitted answer to an expert answer on a given question. Here is the data:
[BEGIN DATA]
************
[Question]: {input}
************
[Expert]: {expected}
************
[Submission]: {output}
************
[END DATA]

Compare the factual content of the submitted answer with the expert answer. Ignore any differences in style, grammar, or punctuation.
The submitted answer may either be a subset or superset of the expert answer, or it may conflict with it. Determine which case applies. Answer the question by selecting one of the following options:
(A) The submitted answer is a subset of the expert answer and is fully consistent with it.
(B) The submitted answer is a superset of the expert answer and is fully consistent with it.
(C) The submitted answer contains all the same details as the expert answer.
(D) There is a disagreement between the submitted answer and the expert answer.
(E) The answers differ, but these differences don't matter from the perspective of factuality.

Answer the question by calling `select_choice` with your reasoning in a step-by-step matter to be
sure that your conclusion is correct. Avoid simply stating the correct answer at the outset. Select a
single choice by setting the `choice` parameter to a single choice from A, B, C, D, or E.
"""

# Since we're testing for hallucinations, penalize (B) as much as (D).
CHOICE_SCORES = {
    "A": 0.5,
    "B": 0,
    "C": 1,
    "D": 0,
    "E": 1,
}


@braintrust.traced
async def classifier(input, output, expected):
    response = await client.chat.completions.create(
        model="gpt-4o",
        messages=[
            {
                "role": "user",
                "content": PROMPT.format(input=input, output=output, expected=expected),
            }
        ],
        temperature=0,
        tools=[
            {
                "type": "function",
                "function": {
                    "name": "rate",
                    "description": "Call this function to select a choice.",
                    "parameters": {
                        "properties": {
                            "reasons": {
                                "description": "Write out in a step by step manner your reasoning to be sure that your conclusion is correct. Avoid simply stating the correct answer at the outset.",
                                "type": "string",
                            },
                            "choice": {
                                "description": "The choice",
                                "type": "string",
                                "enum": ["A", "B", "C", "D", "E"],
                            },
                        },
                        "required": ["reasons", "choice"],
                        "type": "object",
                    },
                },
            }
        ],
        tool_choice={"type": "function", "function": {"name": "rate"}},
    )
    arguments = json.loads(response.choices[0].message.tool_calls[0].function.arguments)
    choice = arguments["choice"]
    return CHOICE_SCORES[choice] if choice in CHOICE_SCORES else None


print(qa_pairs[10].question, "On a correct answer:", qa_pairs[10].generated_answer)
print(
    await classifier(
        qa_pairs[10].question,
        qa_pairs[10].generated_answer,
        qa_pairs[10].expected_answer,
    )
)

print(
    hallucinations[10].question,
    "On a hallucinated answer:",
    hallucinations[10].generated_answer,
)
print(
    await classifier(
        hallucinations[10].question,
        hallucinations[10].generated_answer,
        hallucinations[10].expected_answer,
    )
)

async def task(input):
    return await classifier(
        input=input["question"],
        output=input["generated_answer"],
        expected=input["expected_answer"],
    )


await Eval(
    "LLM-as-a-judge",
    data=data,
    task=task,
    scores=[normalized_diff],
    experiment_name="Classifier",
    max_concurrency=10,
)