126 lines
4.1 KiB
Python
126 lines
4.1 KiB
Python
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import torch
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from torch import nn as nn
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from models.archs.srflow import thops
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class _ActNorm(nn.Module):
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"""
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Activation Normalization
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Initialize the bias and scale with a given minibatch,
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so that the output per-channel have zero mean and unit variance for that.
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After initialization, `bias` and `logs` will be trained as parameters.
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"""
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def __init__(self, num_features, scale=1.):
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super().__init__()
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# register mean and scale
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size = [1, num_features, 1, 1]
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self.register_parameter("bias", nn.Parameter(torch.zeros(*size)))
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self.register_parameter("logs", nn.Parameter(torch.zeros(*size)))
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self.num_features = num_features
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self.scale = float(scale)
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self.inited = False
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def _check_input_dim(self, input):
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return NotImplemented
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def initialize_parameters(self, input):
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self._check_input_dim(input)
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if not self.training:
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return
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if (self.bias != 0).any():
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self.inited = True
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return
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assert input.device == self.bias.device, (input.device, self.bias.device)
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with torch.no_grad():
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bias = thops.mean(input.clone(), dim=[0, 2, 3], keepdim=True) * -1.0
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vars = thops.mean((input.clone() + bias) ** 2, dim=[0, 2, 3], keepdim=True)
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logs = torch.log(self.scale / (torch.sqrt(vars) + 1e-6))
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self.bias.data.copy_(bias.data)
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self.logs.data.copy_(logs.data)
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self.inited = True
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def _center(self, input, reverse=False, offset=None):
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bias = self.bias
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if offset is not None:
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bias = bias + offset
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if not reverse:
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return input + bias
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else:
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return input - bias
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def _scale(self, input, logdet=None, reverse=False, offset=None):
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logs = self.logs
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if offset is not None:
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logs = logs + offset
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if not reverse:
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input = input * torch.exp(logs) # should have shape batchsize, n_channels, 1, 1
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# input = input * torch.exp(logs+logs_offset)
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else:
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input = input * torch.exp(-logs)
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if logdet is not None:
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"""
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logs is log_std of `mean of channels`
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so we need to multiply pixels
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"""
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dlogdet = thops.sum(logs) * thops.pixels(input)
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if reverse:
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dlogdet *= -1
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logdet = logdet + dlogdet
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return input, logdet
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def forward(self, input, logdet=None, reverse=False, offset_mask=None, logs_offset=None, bias_offset=None):
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if not self.inited:
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self.initialize_parameters(input)
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self._check_input_dim(input)
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if offset_mask is not None:
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logs_offset *= offset_mask
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bias_offset *= offset_mask
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# no need to permute dims as old version
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if not reverse:
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# center and scale
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# self.input = input
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input = self._center(input, reverse, bias_offset)
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input, logdet = self._scale(input, logdet, reverse, logs_offset)
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else:
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# scale and center
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input, logdet = self._scale(input, logdet, reverse, logs_offset)
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input = self._center(input, reverse, bias_offset)
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return input, logdet
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class ActNorm2d(_ActNorm):
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def __init__(self, num_features, scale=1.):
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super().__init__(num_features, scale)
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def _check_input_dim(self, input):
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assert len(input.size()) == 4
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assert input.size(1) == self.num_features, (
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"[ActNorm]: input should be in shape as `BCHW`,"
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" channels should be {} rather than {}".format(
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self.num_features, input.size()))
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class MaskedActNorm2d(ActNorm2d):
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def __init__(self, num_features, scale=1.):
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super().__init__(num_features, scale)
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def forward(self, input, mask, logdet=None, reverse=False):
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assert mask.dtype == torch.bool
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output, logdet_out = super().forward(input, logdet, reverse)
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input[mask] = output[mask]
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logdet[mask] = logdet_out[mask]
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return input, logdet
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