code: 
  from __future__ import absolute_import
  
  import sys
  import numpy as np
  import torch
  from torch import nn
  import os
  from collections import OrderedDict
  from torch.autograd import Variable
  import itertools
  from .base_model import BaseModel
  from scipy.ndimage import zoom
  import fractions
  import functools
  import skimage.transform
  from tqdm import tqdm
  
  
  from . import networks_basic as networks
  from . import perceptual_loss
  
  class DistModel(BaseModel):
      def name(self):
          return self.model_name
  
      def initialize(self, model='net-lin', net='alex', colorspace='Lab', pnet_rand=False, pnet_tune=False, model_path=None,
              use_gpu=True, printNet=False, spatial=False, 
              is_train=False, lr=.0001, beta1=0.5, version='0.1', gpu_ids=[0]):
          '''
          INPUTS
              model - ['net-lin'] for linearly calibrated network
                      ['net'] for off-the-shelf network
                      ['L2'] for L2 distance in Lab colorspace
                      ['SSIM'] for ssim in RGB colorspace
              net - ['squeeze','alex','vgg']
              model_path - if None, will look in weights/[NET_NAME].pth
              colorspace - ['Lab','RGB'] colorspace to use for L2 and SSIM
              use_gpu - bool - whether or not to use a GPU
              printNet - bool - whether or not to print network architecture out
              spatial - bool - whether to output an array containing varying distances across spatial dimensions
              is_train - bool - [True] for training mode
              lr - float - initial learning rate
              beta1 - float - initial momentum term for adam
              version - 0.1 for latest, 0.0 was original (with a bug)
              gpu_ids - int array - [0] by default, gpus to use
          '''
          BaseModel.initialize(self, use_gpu=use_gpu, gpu_ids=gpu_ids)
  
          self.model = model
          self.net = net
          self.is_train = is_train
          self.spatial = spatial
          self.gpu_ids = gpu_ids
          self.model_name = '%s [%s]'%(model,net)
  
          if(self.model == 'net-lin'): # pretrained net + linear layer
              self.net = networks.PNetLin(pnet_rand=pnet_rand, pnet_tune=pnet_tune, pnet_type=net,
                  use_dropout=True, spatial=spatial, version=version, lpips=True)
              kw = {}
              if not use_gpu:
                  kw['map_location'] = 'cpu'
              if(model_path is None):
                  import inspect
                  model_path = os.path.abspath(os.path.join(inspect.getfile(self.initialize), '..', 'weights/v%s/%s.pth'%(version,net)))
  
              if(not is_train):
                  print('Loading model from: %s'%model_path)
                  self.net.load_state_dict(torch.load(model_path, **kw), strict=False)
  
          elif(self.model=='net'): # pretrained network
              self.net = networks.PNetLin(pnet_rand=pnet_rand, pnet_type=net, lpips=False)
          elif(self.model in ['L2','l2']):
              self.net = networks.L2(use_gpu=use_gpu,colorspace=colorspace) # not really a network, only for testing
              self.model_name = 'L2'
          elif(self.model in ['DSSIM','dssim','SSIM','ssim']):
              self.net = networks.DSSIM(use_gpu=use_gpu,colorspace=colorspace)
              self.model_name = 'SSIM'
          else:
              raise ValueError("Model [%s] not recognized." % self.model)
  
          self.parameters = list(self.net.parameters())
  
          if self.is_train: # training mode
              # extra network on top to go from distances (d0,d1) => predicted human judgment (h*)
              self.rankLoss = networks.BCERankingLoss()
              self.parameters += list(self.rankLoss.net.parameters())
              self.lr = lr
              self.old_lr = lr
              self.optimizer_net = torch.optim.Adam(self.parameters, lr=lr, betas=(beta1, 0.999))
          else: # test mode
              self.net.eval()
  
          if(use_gpu):
              self.net.to(gpu_ids[0])
              self.net = torch.nn.DataParallel(self.net, device_ids=gpu_ids)
              if(self.is_train):
                  self.rankLoss = self.rankLoss.to(device=gpu_ids[0]) # just put this on GPU0
  
          if(printNet):
              print('---------- Networks initialized -------------')
              networks.print_network(self.net)
              print('-----------------------------------------------')
  
      def forward(self, in0, in1, retPerLayer=False):
          ''' Function computes the distance between image patches in0 and in1
          INPUTS
              in0, in1 - torch.Tensor object of shape Nx3xXxY - image patch scaled to [-1,1]
          OUTPUT
              computed distances between in0 and in1
          '''
  
          return self.net.forward(in0, in1, retPerLayer=retPerLayer)
  
      # ***** TRAINING FUNCTIONS *****
      def optimize_parameters(self):
          self.forward_train()
          self.optimizer_net.zero_grad()
          self.backward_train()
          self.optimizer_net.step()
          self.clamp_weights()
  
      def clamp_weights(self):
          for module in self.net.modules():
              if(hasattr(module, 'weight') and module.kernel_size==(1,1)):
                  module.weight.data = torch.clamp(module.weight.data,min=0)
  
      def set_input(self, data):
          self.input_ref = data['ref']
          self.input_p0 = data['p0']
          self.input_p1 = data['p1']
          self.input_judge = data['judge']
  
          if(self.use_gpu):
              self.input_ref = self.input_ref.to(device=self.gpu_ids[0])
              self.input_p0 = self.input_p0.to(device=self.gpu_ids[0])
              self.input_p1 = self.input_p1.to(device=self.gpu_ids[0])
              self.input_judge = self.input_judge.to(device=self.gpu_ids[0])
  
          self.var_ref = Variable(self.input_ref,requires_grad=True)
          self.var_p0 = Variable(self.input_p0,requires_grad=True)
          self.var_p1 = Variable(self.input_p1,requires_grad=True)
  
      def forward_train(self): # run forward pass
          # print(self.net.module.scaling_layer.shift)
          # print(torch.norm(self.net.module.net.slice1[0].weight).item(), torch.norm(self.net.module.lin0.model[1].weight).item())
  
          self.d0 = self.forward(self.var_ref, self.var_p0)
          self.d1 = self.forward(self.var_ref, self.var_p1)
          self.acc_r = self.compute_accuracy(self.d0,self.d1,self.input_judge)
  
          self.var_judge = Variable(1.*self.input_judge).view(self.d0.size())
  
          self.loss_total = self.rankLoss.forward(self.d0, self.d1, self.var_judge*2.-1.)
  
          return self.loss_total
  
      def backward_train(self):
          torch.mean(self.loss_total).backward()
  
      def compute_accuracy(self,d0,d1,judge):
          ''' d0, d1 are Variables, judge is a Tensor '''
          d1_lt_d0 = (d1<d0).cpu().data.numpy().flatten()
          judge_per = judge.cpu().numpy().flatten()
          return d1_lt_d0*judge_per + (1-d1_lt_d0)*(1-judge_per)
  
      def get_current_errors(self):
          retDict = OrderedDict([('loss_total', self.loss_total.data.cpu().numpy()),
                              ('acc_r', self.acc_r)])
  
          for key in retDict.keys():
              retDict[key] = np.mean(retDict[key])
  
          return retDict
  
      def get_current_visuals(self):
          zoom_factor = 256/self.var_ref.data.size()[2]
  
          ref_img = util.tensor2im(self.var_ref.data)
          p0_img = util.tensor2im(self.var_p0.data)
          p1_img = util.tensor2im(self.var_p1.data)
  
          ref_img_vis = zoom(ref_img,[zoom_factor, zoom_factor, 1],order=0)
          p0_img_vis = zoom(p0_img,[zoom_factor, zoom_factor, 1],order=0)
          p1_img_vis = zoom(p1_img,[zoom_factor, zoom_factor, 1],order=0)
  
          return OrderedDict([('ref', ref_img_vis),
                              ('p0', p0_img_vis),
                              ('p1', p1_img_vis)])
  
      def save(self, path, label):
          if(self.use_gpu):
              self.save_network(self.net.module, path, '', label)
          else:
              self.save_network(self.net, path, '', label)
          self.save_network(self.rankLoss.net, path, 'rank', label)
  
      def update_learning_rate(self,nepoch_decay):
          lrd = self.lr / nepoch_decay
          lr = self.old_lr - lrd
  
          for param_group in self.optimizer_net.param_groups:
              param_group['lr'] = lr
  
          print('update lr [%s] decay: %f -> %f' % (type,self.old_lr, lr))
          self.old_lr = lr
  
  def score_2afc_dataset(data_loader, func, name=''):
      ''' Function computes Two Alternative Forced Choice (2AFC) score using
          distance function 'func' in dataset 'data_loader'
      INPUTS
          data_loader - CustomDatasetDataLoader object - contains a TwoAFCDataset inside
          func - callable distance function - calling d=func(in0,in1) should take 2
              pytorch tensors with shape Nx3xXxY, and return numpy array of length N
      OUTPUTS
          [0] - 2AFC score in [0,1], fraction of time func agrees with human evaluators
          [1] - dictionary with following elements
              d0s,d1s - N arrays containing distances between reference patch to perturbed patches 
              gts - N array in [0,1], preferred patch selected by human evaluators
                  (closer to "0" for left patch p0, "1" for right patch p1,
                  "0.6" means 60pct people preferred right patch, 40pct preferred left)
              scores - N array in [0,1], corresponding to what percentage function agreed with humans
      CONSTS
          N - number of test triplets in data_loader
      '''
  
      d0s = []
      d1s = []
      gts = []
  
      for data in tqdm(data_loader.load_data(), desc=name):
          d0s+=func(data['ref'],data['p0']).data.cpu().numpy().flatten().tolist()
          d1s+=func(data['ref'],data['p1']).data.cpu().numpy().flatten().tolist()
          gts+=data['judge'].cpu().numpy().flatten().tolist()
  
      d0s = np.array(d0s)
      d1s = np.array(d1s)
      gts = np.array(gts)
      scores = (d0s<d1s)*(1.-gts) + (d1s<d0s)*gts + (d1s==d0s)*.5
  
      return(np.mean(scores), dict(d0s=d0s,d1s=d1s,gts=gts,scores=scores))
  
  def score_jnd_dataset(data_loader, func, name=''):
      ''' Function computes JND score using distance function 'func' in dataset 'data_loader'
      INPUTS
          data_loader - CustomDatasetDataLoader object - contains a JNDDataset inside
          func - callable distance function - calling d=func(in0,in1) should take 2
              pytorch tensors with shape Nx3xXxY, and return pytorch array of length N
      OUTPUTS
          [0] - JND score in [0,1], mAP score (area under precision-recall curve)
          [1] - dictionary with following elements
              ds - N array containing distances between two patches shown to human evaluator
              sames - N array containing fraction of people who thought the two patches were identical
      CONSTS
          N - number of test triplets in data_loader
      '''
  
      ds = []
      gts = []
  
      for data in tqdm(data_loader.load_data(), desc=name):
          ds+=func(data['p0'],data['p1']).data.cpu().numpy().tolist()
          gts+=data['same'].cpu().numpy().flatten().tolist()
  
      sames = np.array(gts)
      ds = np.array(ds)
  
      sorted_inds = np.argsort(ds)
      ds_sorted = ds[sorted_inds]
      sames_sorted = sames[sorted_inds]
  
      TPs = np.cumsum(sames_sorted)
      FPs = np.cumsum(1-sames_sorted)
      FNs = np.sum(sames_sorted)-TPs
  
      precs = TPs/(TPs+FPs)
      recs = TPs/(TPs+FNs)
      score = util.voc_ap(recs,precs)
  
      return(score, dict(ds=ds,sames=sames))
  
apis: numpy.sum numpy.cumsum torch.load scipy.ndimage.zoom torch.clamp torch.mean torch.autograd.Variable numpy.argsort torch.optim.Adam numpy.array torch.nn.DataParallel numpy.mean