import torch 
import torch.nn.functional as F 

def exp_d_loss(logits_real, logits_fake):
    loss_real = torch.mean(torch.exp(-logits_real))
    loss_fake = torch.mean(torch.exp(logits_fake))
    d_loss = 0.5 * (loss_real + loss_fake)
    return d_loss

def hinge_d_loss(logits_real, logits_fake):
    loss_real = torch.mean(F.relu(1. - logits_real))
    loss_fake = torch.mean(F.relu(1. + logits_fake))
    d_loss = 0.5 * (loss_real + loss_fake)
    return d_loss

def vanilla_d_loss(logits_real, logits_fake):
    d_loss = 0.5 * (
        torch.mean(F.softplus(-logits_real)) +
        torch.mean(F.softplus(logits_fake)))
    return d_loss