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mmd.py
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mmd.py
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#!/usr/bin/env python
# encoding: utf-8
import torch
def guassian_kernel(source, target, kernel_mul=2.0, kernel_num=5, fix_sigma=None):
n_samples = int(source.size()[0])+int(target.size()[0])
total = torch.cat([source, target], dim=0)
total0 = total.unsqueeze(0).expand(int(total.size(0)), int(total.size(0)), int(total.size(1)))
total1 = total.unsqueeze(1).expand(int(total.size(0)), int(total.size(0)), int(total.size(1)))
L2_distance = ((total0-total1)**2).sum(2)
if fix_sigma:
bandwidth = fix_sigma
else:
bandwidth = torch.sum(L2_distance.data) / (n_samples**2-n_samples)
bandwidth /= kernel_mul ** (kernel_num // 2)
bandwidth_list = [bandwidth * (kernel_mul**i) for i in range(kernel_num)]
kernel_val = [torch.exp(-L2_distance / bandwidth_temp) for bandwidth_temp in bandwidth_list]
return sum(kernel_val)#/len(kernel_val)
def mmd_rbf_accelerate(source, target, kernel_mul=2.0, kernel_num=5, fix_sigma=None):
batch_size = int(source.size()[0])
kernels = guassian_kernel(source, target,
kernel_mul=kernel_mul, kernel_num=kernel_num, fix_sigma=fix_sigma)
loss = 0
for i in range(batch_size):
s1, s2 = i, (i+1)%batch_size
t1, t2 = s1+batch_size, s2+batch_size
loss += kernels[s1, s2] + kernels[t1, t2]
loss -= kernels[s1, t2] + kernels[s2, t1]
return loss / float(batch_size)
def mmd_rbf_noaccelerate(source, target, kernel_mul=2.0, kernel_num=5, fix_sigma=None):
batch_size = int(source.size()[0])
#print(batch_size)
kernels = guassian_kernel(source, target,
kernel_mul=kernel_mul, kernel_num=kernel_num, fix_sigma=fix_sigma)
XX = kernels[:batch_size, :batch_size]
YY = kernels[batch_size:, batch_size:]
XY = kernels[:batch_size, batch_size:]
YX = kernels[batch_size:, :batch_size]
#print(XX.shape,YY.shape,XY.shape,YX.shape)
loss = torch.mean(XX + YY - XY -YX)
return loss