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"""Model class template
This module provides a template for users to implement custom models.
You can specify '--model template' to use this model.
The class name should be consistent with both the filename and its model option.
The filename should be <model>_dataset.py
The class name should be <Model>Dataset.py
It implements a simple image-to-image translation baseline based on regression loss.
Given input-output pairs (data_A, data_B), it learns a network netG that can minimize the following L1 loss:
min_<netG> ||netG(data_A) - data_B||_1
You need to implement the following functions:
<modify_commandline_options>: Add model-specific options and rewrite default values for existing options.
<__init__>: Initialize this model class.
<set_input>: Unpack input data and perform data pre-processing.
<forward>: Run forward pass. This will be called by both <optimize_parameters> and <test>.
<optimize_parameters>: Update network weights; it will be called in every training iteration.
"""
import numpy as np
import torch
from .base_model import BaseModel
from . import networks
class TemplateModel(BaseModel):
@staticmethod
def modify_commandline_options(parser, is_train=True):
"""Add new model-specific options and rewrite default values for existing options.
Parameters:
parser -- the option parser
is_train -- if it is training phase or test phase. You can use this flag to add training-specific or test-specific options.
Returns:
the modified parser.
"""
parser.set_defaults(dataset_mode='aligned') # You can rewrite default values for this model. For example, this model usually uses aligned dataset as its dataset.
if is_train:
parser.add_argument('--lambda_regression', type=float, default=1.0, help='weight for the regression loss') # You can define new arguments for this model.
return parser
def __init__(self, opt):
"""Initialize this model class.
Parameters:
opt -- training/test options
A few things can be done here.
- (required) call the initialization function of BaseModel
- define loss function, visualization images, model names, and optimizers
"""
BaseModel.__init__(self, opt) # call the initialization method of BaseModel
# specify the training losses you want to print out. The program will call base_model.get_current_losses to plot the losses to the console and save them to the disk.
self.loss_names = ['loss_G']
# specify the images you want to save and display. The program will call base_model.get_current_visuals to save and display these images.
self.visual_names = ['data_A', 'data_B', 'output']
# specify the models you want to save to the disk. The program will call base_model.save_networks and base_model.load_networks to save and load networks.
# you can use opt.isTrain to specify different behaviors for training and test. For example, some networks will not be used during test, and you don't need to load them.
self.model_names = ['G']
# define networks; you can use opt.isTrain to specify different behaviors for training and test.
self.netG = networks.define_G(opt.input_nc, opt.output_nc, opt.ngf, opt.netG, gpu_ids=self.gpu_ids)
if self.isTrain: # only defined during training time
# define your loss functions. You can use losses provided by torch.nn such as torch.nn.L1Loss.
# We also provide a GANLoss class "networks.GANLoss". self.criterionGAN = networks.GANLoss().to(self.device)
self.criterionLoss = torch.nn.L1Loss()
# define and initialize optimizers. You can define one optimizer for each network.
# If two networks are updated at the same time, you can use itertools.chain to group them. See cycle_gan_model.py for an example.
self.optimizer = torch.optim.Adam(self.netG.parameters(), lr=opt.lr, betas=(opt.beta1, 0.999))
self.optimizers = [self.optimizer]
# Our program will automatically call <model.setup> to define schedulers, load networks, and print networks
def set_input(self, input):
"""Unpack input data from the dataloader and perform necessary pre-processing steps.
Parameters:
input: a dictionary that contains the data itself and its metadata information.
"""
AtoB = self.opt.direction == 'AtoB' # use <direction> to swap data_A and data_B
self.data_A = input['A' if AtoB else 'B'].to(self.device) # get image data A
self.data_B = input['B' if AtoB else 'A'].to(self.device) # get image data B
self.image_paths = input['A_paths' if AtoB else 'B_paths'] # get image paths
def forward(self):
"""Run forward pass. This will be called by both functions <optimize_parameters> and <test>."""
self.output = self.netG(self.data_A) # generate output image given the input data_A
def backward(self):
"""Calculate losses, gradients, and update network weights; called in every training iteration"""
# caculate the intermediate results if necessary; here self.output has been computed during function <forward>
# calculate loss given the input and intermediate results
self.loss_G = self.criterionLoss(self.output, self.data_B) * self.opt.lambda_regression
self.loss_G.backward() # calculate gradients of network G w.r.t. loss_G
def optimize_parameters(self):
"""Update network weights; it will be called in every training iteration."""
self.forward() # first call forward to calculate intermediate results
self.optimizer.zero_grad() # clear network G's existing gradients
self.backward() # calculate gradients for network G
self.optimizer.step() # update gradients for network G
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