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import torch
import torch.nn.functional as F
from typing import Dict, Tuple
import numpy as np
class GEELoss:
def __init__(self, lambda_weight: float = 3.0, use_l1: bool = False):
self.lambda_weight = lambda_weight
self.use_l1 = use_l1
def compute_token_entropy(self, logits: torch.Tensor,
attention_mask: torch.Tensor = None) -> torch.Tensor:
"""计算token级别的条件熵"""
probs = F.softmax(logits, dim=-1)
log_probs = F.log_softmax(logits, dim=-1)
H_tok = -(probs * log_probs).sum(-1) # (B, T)
if attention_mask is not None:
H_tok = H_tok * attention_mask
return H_tok
def compute_sample_entropy(self, H_tok: torch.Tensor,
prompt_lengths: torch.Tensor) -> torch.Tensor:
"""计算样本平均熵"""
batch_size = H_tok.size(0)
H_i = torch.zeros(batch_size, device=H_tok.device)
for i in range(batch_size):
# 只计算生成部分的熵（排除prompt部分）
gen_start = prompt_lengths[i]
if gen_start < H_tok.size(1):
gen_entropy = H_tok[i, gen_start:]
# 过滤掉padding token的熵
valid_entropy = gen_entropy[gen_entropy != 0]
if valid_entropy.numel() > 0:
H_i[i] = valid_entropy.mean()
return H_i
def compute_group_entropy(self, H_i: torch.Tensor,
gender_labels: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
"""计算各组平均熵"""
male_mask = (gender_labels == 0) # 假设0=male, 1=female
female_mask = (gender_labels == 1)
H_male = H_i[male_mask].mean() if male_mask.sum() > 0 else torch.tensor(0.0, device=H_i.device)
H_female = H_i[female_mask].mean() if female_mask.sum() > 0 else torch.tensor(0.0, device=H_i.device)
return H_male, H_female
def compute_gee_loss(self, H_i: torch.Tensor,
gender_labels: torch.Tensor) -> Tuple[torch.Tensor, Dict]:
"""计算GEE损失"""
H_bar = H_i.mean() # 全批平均熵
# 计算各组平均熵
H_male, H_female = self.compute_group_entropy(H_i, gender_labels)
# 计算组间差异
if self.use_l1:
# L1版本
group_diff = torch.abs(H_female - H_male)
loss_bias = group_diff
else:
# L2版本
H_bar_group = (H_male + H_female) / 2
loss_bias = (H_male - H_bar_group) ** 2 + (H_female - H_bar_group) ** 2
# 总损失
loss_em = H_bar
loss_total = loss_em + self.lambda_weight * loss_bias
# 返回损失和监控指标
metrics = {
'loss_em': loss_em.item(),
'loss_bias': loss_bias.item(),
'loss_total': loss_total.item(),
'H_bar': H_bar.item(),
'H_male': H_male.item(),
'H_female': H_female.item(),
'entropy_gap': abs(H_female - H_male).item()
}
return loss_total, metrics
def update_lambda(self, new_lambda: float):
"""更新lambda权重（用于自动退火）"""
self.lambda_weight = new_lambda
def gender_to_label(gender_str: str) -> int:
"""将性别字符串转换为标签"""
return 0 if gender_str == 'male' else 1
def label_to_gender(label: int) -> str:
"""将标签转换为性别字符串"""
return 'male' if label == 0 else 'female'
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