M.S.です。大規模言語モデル（以降LLM）の幻覚を軽減する方法について、Meta AI によって出された論文の実装を行いました。

TL;DR

• 自然言語生成モデルのハルシネーションには、以下の問題がある。
  
  • 効果的なメトリクスがない
  • 一次情報を参照するという解決策が却ってハルシネーションを誘発することがある
• 一次情報を参照せずに、ハルシネーションを軽減する試みとして自己検証をする仕組みを持つChain-of-Verification (CoVe)を紹介する。
• CoVeをLangChainを用いて実装してみた。

自然言語モデルの幻覚（ハルシネーション）とは

QA生成の幻覚

1. 性能指標が確立されていない。
   ROUGEスコアやF1スコアなどの自動評価指標を使用しているがこれらの指標は、そもそもタスクの性能指標であることが多く、ハルシネーション特有の性能指標が確立されていません。また、それらの指標は人間の判断との低い相関のようです。

2. 幻覚を軽減するために一次情報を参照するという方法が幻覚の原因となる可能性がある。
   様々な情報を参照すると、ソース情報の質の低さや矛盾によってハルシネーションが起きやすくなります。

検索に頼らない幻覚の軽減方法

特長

方法

1. ベースライン応答の生成: クエリが与えられた場合、LLMを使用して応答を生成します。
2. 検証の計画: クエリとベースラインの応答の両方が与えられた場合、元の応答にミスがないか自己分析するのに役立つ検証の質問のリストを生成します。
3. 検証の実行: それぞれの検証の質問に答え、元の応答と照らし合わせて矛盾やミスがないか確認します。
4. 最終確認済み応答の生成: 発見された矛盾（もしあれば）を元に、検証結果を取り入れて修正された応答を生成します。

実装

ライブラリのインストール

import os
from langchain.llms import OpenAI
from langchain.chains import SequentialChain
from langchain.chains import LLMChain
from langchain.prompts import PromptTemplate
# openAIのAPI　keyを準備する必要あり
os.environ["OPENAI_API_KEY"] = "..."

llmの指定

llm = OpenAI(temperature=0)

templateの作成

baseline_prompt = PromptTemplate(
    input_variables=['person'],
    template="""
    Q: tell me a bio of Kishida Fumio
    A: Fumio Kishida is a Japanese politician who, as of January 2021, serves as the Prime Minister of Japan. Born in Tokyo in 1956, he graduated from Waseda University. In October 2021, he succeeded Yoshihide Suga as the president of the Liberal Democratic Party (LDP) and subsequently became the Prime Minister of Japan.

    Q: tell me a bio of Kan Naoto
    A: Naoto Kan is a Japanese politician who served as the Prime Minister of Japan from 2010 to 2011. Born in Hiroshima, in 1946, he graduated from the Tokyo Institute of Technology. 
    
    Q: tell me a bio of {person}
    A:

    """
)

plan_verification_prompt = PromptTemplate(
    input_variables=['baseline_answer'],
    template="""
    Context: Q: tell me a bio of Kishida Fumio
    A: Fumio Kishida is a Japanese politician who, as of January 2021, serves as the Prime Minister of Japan. Born in Tokyo in 1956, he graduated from Waseda University. In October 2021, he succeeded Yoshihide Suga as the president of the Liberal Democratic Party (LDP) and subsequently became the Prime Minister of Japan.
    Verification response:
    When Fumio Kishida was born?
    Where Fumio Kishida was born?
    Which university did Fumio Kishida graduate from?

    
    Context: Q: tell me a bio of Kan Naoto
    A: Naoto Kan is a Japanese politician who served as the Prime Minister of Japan from 2010 to 2011. Born in Hiroshima, in 1946, he graduated from the Tokyo Institute of Technology. 
    Verification response:
    When Naoto Kan was born?
    Where Naoto Kan was born?
    Which university did Naoto Kan graduate from?


    Context: Q: tell me a bio of K
    A: {baseline_answer}
    Response:
    """
)

execute_verification_prompt = PromptTemplate(
    input_variables=['plan_verification'],
    template="""
    Q: When Fumio Kishida was born?
    A: 1957.
    Q: Where Naoto Kan was born?
    A: Yamaguchi.
    Q: Which university did Fumio Kishida graduate from?
    A: Tokyo University.
    Q: {plan_verification}
    A: 
    """
)

verified_template = PromptTemplate(
    input_variables=['baseline_answer','plan_verification','execute_verification'],
    template="""
    Context: Fumio Kishida is a Japanese politician who, as of January 2021, serves as the Prime Minister of Japan. Born in Tokyo in 1956, he graduated from Waseda University. In October 2021, he succeeded Yoshihide Suga as the president of the Liberal Democratic Party (LDP) and subsequently became the Prime Minister of Japan.
    From another source,
    Q: When Fumio Kishida was born?
    A: 1957.
    Q: Where Fumio Kishida was born?
    A: Tokyo.
    Q: Which university did Fumio Kishida graduate from?
    A: Tokyo University.
    Response: Fumio Kishida is a Japanese politician who, as of January 2021, serves as the Prime Minister of Japan. Born in Tokyo in 1957, he graduated from Waseda University. In October 2021, he succeeded Yoshihide Suga as the president of the Liberal Democratic Party (LDP) and subsequently became the Prime Minister of Japan.
    
    Context: Naoto Kan is a Japanese politician who served as the Prime Minister of Japan from 2010 to 2011. Born in Hiroshima, in 1946, he graduated from the Tokyo Institute of Technology. 
    From another source,
    Q: When Naoto Kan was born?
    A: 1946.
    Q: Where Naoto Kan was born?
    A: Yamaguchi.
    Q: Which university did Naoto Kan graduate from?
    A: Tokyo Institute of Technology.
    Response: Naoto Kan is a Japanese politician who served as the Prime Minister of Japan from 2010 to 2011. Born in Yamaguchi, in 1946, he graduated from the Tokyo Institute of Technology. 
    

    Context: {baseline_answer}.
    From another source,
    {plan_verification}
    {execute_verification}
    Response:
    """
)

LLMchainの作成

baseline_answer_chain = LLMChain(
    llm = llm,
    prompt=baseline_prompt,
    output_key='baseline_answer'
)
plan_verification_chain = LLMChain(
    llm = llm,
    prompt=plan_verification_prompt,
    output_key='plan_verification'
)
execute_verification_chain = LLMChain(
    llm = llm,
    prompt=execute_verification_prompt,
    output_key='execute_verification'
)
final_verified_chain = LLMChain(
    llm = llm,
    prompt=verified_template,
    output_key='final_verification'
)

SequentialChainで接続する

overall_chain = SequentialChain(
    chains=[baseline_answer_chain, plan_verification_chain, execute_verification_chain, final_verified_chain],
    input_variables=['person'],
    output_variables=['baseline_answer','plan_verification','execute_verification','final_verification'],
    verbose=True
)

実行

print(overall_chain({'person': 'Mori Yoshiro'}))

実行結果

'person': 'Mori Yoshiro', 

'baseline_answer': " Yoshiro Mori is a Japanese politician who served as the Prime Minister of Japan from 2000 to 2001. Born in Tokyo in 1937, he graduated from the University of Tokyo. He was the longest-serving president of the Liberal Democratic Party (LDP) from 1999 to 2001. He also served as the president of the Japan-Korea Parliamentarians' Union from 2001 to 2006.", 

'plan_verification': ' When was Yoshiro Mori born?\n     Where was Yoshiro Mori born?\n     Which university did Yoshiro Mori graduate from?', 

'execute_verification': ' When: 1937\n     Where: Tokyo\n     University: Waseda University', 

'final_verification': " Yoshiro Mori is a Japanese politician who served as the Prime Minister of Japan from 2000 to 2001. Born in Tokyo in 1937, he graduated from the Waseda University. He was the longest-serving president of the Liberal Democratic Party (LDP) from 1999 to 2001. He also served as the president of the Japan-Korea Parliamentarians' Union from 2001 to 2006."}

参考資料

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