sample-evaluation-scripts/llm_judge.py

"""
LLM-as-a-judge scoring.

A judge model decides whether the response is semantically equivalent to the
golden answer, and returns a TRUE/FALSE verdict with a short justification.
Unlike the two deterministic scripts, this accepts paraphrases, alternate
spellings, and transliteration variants.

The judge used for the reported results was Gemma 3 12B. This script is
provider-agnostic: implement `call_model()` for whatever backend you use, then
run as normal.

Usage:
    python llm_judge.py --responses my_model_english.csv
    python llm_judge.py --responses my_model_english.csv --limit 50 --out scored.csv

Input CSV: the language file from this dataset (columns `question`, `answer`,
`Domain`) with a `response` column added holding the model's raw output.
"""

import argparse
import json
import re
import sys

import pandas as pd

REQUIRED = ["question", "answer", "Domain", "response"]

JUDGE_PROMPT = """You are an evaluation judge. Your task is to determine if the given answer matches the ground truth answer for the given question.

## Input
Question: {question}
Ground Truth Answer: {ground_truth_answer}
Given Answer: {llm_answer}

## Instructions
1. Compare the "Given Answer" against the "Ground Truth Answer" in the context of the question.
2. Correct if semantically equivalent (same meaning / same entity or fact).
3. Minor phrasing, formatting, or extra detail is acceptable if the core answer is correct.
4. Clearly wrong, meaning-changing, or unrelated answers are incorrect.
5. Answers in a different language than the question and ground truth are incorrect.

## Output Format
Return ONLY a JSON object (no additional text, no markdown fences):
{{"is_correct": true, "reasoning": "brief explanation"}}"""


# ---------------------------------------------------------------------------
# IMPLEMENT THIS
# ---------------------------------------------------------------------------

def call_model(prompt: str) -> str:
    """
    Send `prompt` to the judge model and return its raw text response.

    Replace the body with a call to whichever backend you use. Two sketches:

    Local, via transformers:

        from transformers import pipeline
        pipe = pipeline("text-generation", model="google/gemma-3-12b-it",
                        device_map="auto", max_new_tokens=200)
        return pipe(prompt)[0]["generated_text"][len(prompt):]

    Any OpenAI-compatible endpoint (including local vLLM or Ollama):

        from openai import OpenAI
        client = OpenAI(base_url="http://localhost:8000/v1", api_key="...")
        out = client.chat.completions.create(
            model="google/gemma-3-12b-it",
            messages=[{"role": "user", "content": prompt}],
            temperature=0,
        )
        return out.choices[0].message.content

    Use a temperature of 0 or the closest equivalent: the judge should be as
    close to deterministic as the backend allows, or scores will not reproduce.
    """
    raise NotImplementedError(
        "call_model() is a stub. Implement it for your backend before running "
        "this script. See the docstring above for two examples."
    )


# ---------------------------------------------------------------------------

def parse_verdict(raw: str):
    """
    Pull {"is_correct": bool, "reasoning": str} out of the judge's output.

    Models sometimes wrap JSON in markdown fences or add a sentence around it
    despite the instruction, so fall back to locating the first JSON object.
    Returns (is_correct, reasoning); is_correct is None if parsing failed.
    """
    text = raw.strip()
    text = re.sub(r"^```(?:json)?\s*|\s*```$", "", text, flags=re.MULTILINE).strip()

    try:
        obj = json.loads(text)
    except json.JSONDecodeError:
        match = re.search(r"\{.*?\}", text, flags=re.DOTALL)
        if not match:
            return None, f"unparseable judge output: {raw[:120]}"
        try:
            obj = json.loads(match.group(0))
        except json.JSONDecodeError:
            return None, f"unparseable judge output: {raw[:120]}"

    verdict = obj.get("is_correct")
    if isinstance(verdict, str):
        verdict = verdict.strip().lower() in ("true", "yes", "1")
    if not isinstance(verdict, bool):
        return None, f"missing or non-boolean is_correct: {raw[:120]}"

    return verdict, str(obj.get("reasoning", ""))


def judge_row(question, answer, response):
    prompt = JUDGE_PROMPT.format(question=question,
                                 ground_truth_answer=answer,
                                 llm_answer=response)
    return parse_verdict(call_model(prompt))


def report(df, label):
    """Print per-domain and combined accuracy."""
    scored = df[df["is_correct"].notna()].copy()
    scored["is_correct"] = scored["is_correct"].astype(bool)
    per_domain = scored.groupby("Domain")["is_correct"].agg(["sum", "size"])

    print(f"\n{label}\n")
    print(f"{'Domain':<20} {'Correct':>8} {'Total':>7} {'Accuracy':>10}")
    print("-" * 48)
    for domain, row in per_domain.iterrows():
        acc = row["sum"] / row["size"] * 100
        print(f"{domain:<20} {int(row['sum']):>8} {int(row['size']):>7} {acc:>9.2f}%")

    correct, total = int(scored["is_correct"].sum()), len(scored)
    print("-" * 48)
    if total:
        print(f"{'COMBINED':<20} {correct:>8} {total:>7} {correct / total * 100:>9.2f}%")
    print("\nCombined is the micro-average over all pooled questions, which is")
    print("identical to weighting each domain by its size.")

    failed = len(df) - total
    if failed:
        print(f"\nWarning: {failed} row(s) produced unparseable judge output and are")
        print("excluded from the accuracy above. Inspect them before reporting a score.")


def main():
    ap = argparse.ArgumentParser(description=__doc__,
                                 formatter_class=argparse.RawDescriptionHelpFormatter)
    ap.add_argument("--responses", required=True,
                    help="CSV with columns: question, answer, Domain, response")
    ap.add_argument("--out", help="Optional path to write per-question verdicts")
    ap.add_argument("--limit", type=int,
                    help="Judge only the first N rows (useful for a smoke test)")
    args = ap.parse_args()

    df = pd.read_csv(args.responses)

    missing = [c for c in REQUIRED if c not in df.columns]
    if missing:
        sys.exit(f"Error: {args.responses} is missing column(s): {', '.join(missing)}\n"
                 f"Found: {', '.join(df.columns)}")

    if args.limit:
        df = df.head(args.limit).copy()

    verdicts, reasons = [], []
    for i, row in enumerate(df.itertuples(index=False), start=1):
        verdict, reason = judge_row(row.question, row.answer, row.response)
        verdicts.append(verdict)
        reasons.append(reason)
        if i % 50 == 0 or i == len(df):
            print(f"  judged {i}/{len(df)}", file=sys.stderr)

    df["is_correct"] = verdicts
    df["judge_reasoning"] = reasons

    report(df, f"LLM as a judge — {args.responses}")

    if args.out:
        df.to_csv(args.out, index=False)
        print(f"\nPer-question verdicts written to {args.out}")


if __name__ == "__main__":
    main()