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278 | class PairwiseComparisonEvaluator(BaseEvaluator):
"""Pairwise comparison evaluator.
Evaluates the quality of a response vs. a "reference" response given a question by
having an LLM judge which response is better.
Outputs whether the `response` given is better than the `reference` response.
Args:
eval_template (Optional[Union[str, BasePromptTemplate]]):
The template to use for evaluation.
enforce_consensus (bool): Whether to enforce consensus (consistency if we
flip the order of the answers). Defaults to True.
"""
def __init__(
self,
llm: Optional[LLM] = None,
eval_template: Optional[Union[BasePromptTemplate, str]] = None,
parser_function: Callable[
[str], Tuple[Optional[bool], Optional[float], Optional[str]]
] = _default_parser_function,
enforce_consensus: bool = True,
) -> None:
self._llm = llm or Settings.llm
self._eval_template: BasePromptTemplate
if isinstance(eval_template, str):
self._eval_template = PromptTemplate(eval_template)
else:
self._eval_template = eval_template or DEFAULT_EVAL_TEMPLATE
self._enforce_consensus = enforce_consensus
self._parser_function = parser_function
def _get_prompts(self) -> PromptDictType:
"""Get prompts."""
return {
"eval_template": self._eval_template,
}
def _update_prompts(self, prompts: PromptDictType) -> None:
"""Update prompts."""
if "eval_template" in prompts:
self._eval_template = prompts["eval_template"]
async def _get_eval_result(
self,
query: str,
response: str,
second_response: str,
reference: Optional[str],
) -> EvaluationResult:
"""Get evaluation result."""
eval_response = await self._llm.apredict(
prompt=self._eval_template,
query=query,
answer_1=response,
answer_2=second_response,
reference=reference or "",
)
# Extract from response
passing, score, feedback = self._parser_function(eval_response)
if passing is None and score is None and feedback is None:
return EvaluationResult(
query=query,
invalid_result=True,
invalid_reason="Output cannot be parsed",
feedback=eval_response,
)
else:
return EvaluationResult(
query=query,
response=eval_response,
passing=passing,
score=score,
feedback=eval_response,
pairwise_source=EvaluationSource.ORIGINAL,
)
async def _resolve_results(
self,
eval_result: EvaluationResult,
flipped_eval_result: EvaluationResult,
) -> EvaluationResult:
"""Resolve eval results from evaluation + flipped evaluation.
Args:
eval_result (EvaluationResult): Result when answer_1 is shown first
flipped_eval_result (EvaluationResult): Result when answer_2 is shown first
Returns:
EvaluationResult: The final evaluation result
"""
# add pairwise_source to eval_result and flipped_eval_result
eval_result.pairwise_source = EvaluationSource.ORIGINAL
flipped_eval_result.pairwise_source = EvaluationSource.FLIPPED
# count the votes for each of the 2 answers
votes_1 = 0.0
votes_2 = 0.0
if eval_result.score is not None and flipped_eval_result.score is not None:
votes_1 = eval_result.score + (1 - flipped_eval_result.score)
votes_2 = (1 - eval_result.score) + flipped_eval_result.score
if votes_1 + votes_2 != 2: # each round, the judge can give a total of 1 vote
raise ValueError("Impossible score results. Total amount of votes is 2.")
# get the judges (original and flipped) who voted for answer_1
voters_1 = [eval_result] * (eval_result.score == 1.0) + [
flipped_eval_result
] * (flipped_eval_result.score == 0.0)
# get the judges (original and flipped) who voted for answer_2
voters_2 = [eval_result] * (eval_result.score == 0.0) + [
flipped_eval_result
] * (flipped_eval_result.score == 1.0)
if votes_1 > votes_2:
return voters_1[0] # return any voter for answer_1
elif votes_2 > votes_1:
return voters_2[0] # return any vote for answer_2
else:
if (
eval_result.score == 0.5
): # votes_1 == votes_2 can only happen if both are 1.0 (so actual tie)
# doesn't matter which one we return here
return eval_result
else: # Inconclusive case!
return EvaluationResult(
query=eval_result.query,
response="",
passing=None,
score=0.5,
feedback="",
pairwise_source=EvaluationSource.NEITHER,
)
async def aevaluate(
self,
query: Optional[str] = None,
response: Optional[str] = None,
contexts: Optional[Sequence[str]] = None,
second_response: Optional[str] = None,
reference: Optional[str] = None,
sleep_time_in_seconds: int = 0,
**kwargs: Any,
) -> EvaluationResult:
del kwargs # Unused
del contexts # Unused
if query is None or response is None or second_response is None:
raise ValueError(
"query, response, second_response, and reference must be provided"
)
await asyncio.sleep(sleep_time_in_seconds)
eval_result = await self._get_eval_result(
query, response, second_response, reference
)
if self._enforce_consensus and not eval_result.invalid_result:
# Flip the order of the answers and see if the answer is consistent
# (which means that the score should flip from 0 to 1 and vice-versa)
# if not, then we return a tie
flipped_eval_result = await self._get_eval_result(
query, second_response, response, reference
)
if not flipped_eval_result.invalid_result:
resolved_eval_result = await self._resolve_results(
eval_result, flipped_eval_result
)
else:
resolved_eval_result = EvaluationResult(
query=eval_result.query,
response=eval_result.response,
feedback=flipped_eval_result.response,
invalid_result=True,
invalid_reason="Output cannot be parsed.",
)
else:
resolved_eval_result = eval_result
return resolved_eval_result
|
