这是我的客户目标功能，我想在lightgbm中添加“焦点损失”。
###############我的代码from numpy import log
def grad_func(y_true,y_pred):
if y_true==1:
return -0.5*(2y_pred - 2)log(y_pred) - 0.5(-y_pred + 1)**2/y_pred
if y_true==0:
return 0.5y_pred**2/(-y_pred + 1) - 1.0y_predlog(-y_pred + 1)
def hess_func(y_true,y_pred):
if y_true==1:
return -1.0log(y_pred) - (2.0y_pred - 2.0)/y_pred + 0.5*(y_pred - 1)2/y_pred2
if y_true==0:
return 0.5y_pred**2/(y_pred - 1)**2 - 2.0y_pred/(y_pred - 1) - 1.0*log(-y_pred + 1)
def focal_loss(y_true,y_pred):
gamma=2.0
alpha=0.5
y_true=y_true.tolist()
y_pred=y_pred.tolist()
grad=[]
hess=[]
for i in range(len(y_true)):
if y_pred[i]==0:
y_pred[i]=y_pred[i]+1e-12 ## avoid that the y_pred==0
#and can not be divided
grad.append(grad_func(y_true[i],y_pred[i]))
hess.append(hess_func(y_true[i],y_pred[i]))
return np.array(grad),np.array(hess)
它可以工作，但始终像小偷一样工作 enter image description here
