CustomLayers.py

"""
-------------------------------------------------
   File Name:    CustomLayers.py
   Date:         2019/10/17
   Description:  Copy from: https://github.com/lernapparat/lernapparat
-------------------------------------------------
"""

import numpy as np
from collections import OrderedDict

import torch
import torch.nn as nn
import torch.nn.functional as F


class PixelNormLayer(nn.Module):
    def __init__(self, epsilon=1e-8):
        super().__init__()
        self.epsilon = epsilon

    def forward(self, x):
        return x * torch.rsqrt(torch.mean(x ** 2, dim=1, keepdim=True) + self.epsilon)


class Upscale2d(nn.Module):
    @staticmethod
    def upscale2d(x, factor=2, gain=1):
        assert x.dim() == 4
        if gain != 1:
            x = x * gain
        if factor != 1:
            shape = x.shape
            x = x.view(shape[0], shape[1], shape[2], 1, shape[3], 1).expand(-1, -1, -1, factor, -1, factor)
            x = x.contiguous().view(shape[0], shape[1], factor * shape[2], factor * shape[3])
        return x

    def __init__(self, factor=2, gain=1):
        super().__init__()
        assert isinstance(factor, int) and factor >= 1
        self.gain = gain
        self.factor = factor

    def forward(self, x):
        return self.upscale2d(x, factor=self.factor, gain=self.gain)


class Downscale2d(nn.Module):
    def __init__(self, factor=2, gain=1):
        super().__init__()
        assert isinstance(factor, int) and factor >= 1
        self.factor = factor
        self.gain = gain
        if factor == 2:
            f = [np.sqrt(gain) / factor] * factor
            self.blur = BlurLayer(kernel=f, normalize=False, stride=factor)
        else:
            self.blur = None

    def forward(self, x):
        assert x.dim() == 4
        # 2x2, float32 => downscale using _blur2d().
        if self.blur is not None and x.dtype == torch.float32:
            return self.blur(x)

        # Apply gain.
        if self.gain != 1:
            x = x * self.gain

        # No-op => early exit.
        if self.factor == 1:
            return x

        # Large factor => downscale using tf.nn.avg_pool().
        # NOTE: Requires tf_config['graph_options.place_pruned_graph']=True to work.
        return F.avg_pool2d(x, self.factor)


class EqualizedLinear(nn.Module):
    """Linear layer with equalized learning rate and custom learning rate multiplier."""

    def __init__(self, input_size, output_size, gain=2 ** 0.5, use_wscale=False, lrmul=1, bias=True):
        super().__init__()
        he_std = gain * input_size ** (-0.5)  # He init
        # Equalized learning rate and custom learning rate multiplier.
        if use_wscale:
            init_std = 1.0 / lrmul
            self.w_mul = he_std * lrmul
        else:
            init_std = he_std / lrmul
            self.w_mul = lrmul
        self.weight = torch.nn.Parameter(torch.randn(output_size, input_size) * init_std)
        if bias:
            self.bias = torch.nn.Parameter(torch.zeros(output_size))
            self.b_mul = lrmul
        else:
            self.bias = None

    def forward(self, x):
        bias = self.bias
        if bias is not None:
            bias = bias * self.b_mul
        return F.linear(x, self.weight * self.w_mul, bias)


class EqualizedConv2d(nn.Module):
    """Conv layer with equalized learning rate and custom learning rate multiplier."""

    def __init__(self, input_channels, output_channels, kernel_size, stride=1, gain=2 ** 0.5, use_wscale=False,
                 lrmul=1, bias=True, intermediate=None, upscale=False, downscale=False):
        super().__init__()
        if upscale:
            self.upscale = Upscale2d()
        else:
            self.upscale = None
        if downscale:
            self.downscale = Downscale2d()
        else:
            self.downscale = None
        he_std = gain * (input_channels * kernel_size ** 2) ** (-0.5)  # He init
        self.kernel_size = kernel_size
        if use_wscale:
            init_std = 1.0 / lrmul
            self.w_mul = he_std * lrmul
        else:
            init_std = he_std / lrmul
            self.w_mul = lrmul
        self.weight = torch.nn.Parameter(
            torch.randn(output_channels, input_channels, kernel_size, kernel_size) * init_std)
        if bias:
            self.bias = torch.nn.Parameter(torch.zeros(output_channels))
            self.b_mul = lrmul
        else:
            self.bias = None
        self.intermediate = intermediate

    def forward(self, x):
        bias = self.bias
        if bias is not None:
            bias = bias * self.b_mul

        have_convolution = False
        if self.upscale is not None and min(x.shape[2:]) * 2 >= 128:
            # this is the fused upscale + conv from StyleGAN, sadly this seems incompatible with the non-fused way
            # this really needs to be cleaned up and go into the conv...
            w = self.weight * self.w_mul
            w = w.permute(1, 0, 2, 3)
            # probably applying a conv on w would be more efficient. also this quadruples the weight (average)?!
            w = F.pad(w, [1, 1, 1, 1])
            w = w[:, :, 1:, 1:] + w[:, :, :-1, 1:] + w[:, :, 1:, :-1] + w[:, :, :-1, :-1]
            x = F.conv_transpose2d(x, w, stride=2, padding=(w.size(-1) - 1) // 2)
            have_convolution = True
        elif self.upscale is not None:
            x = self.upscale(x)

        downscale = self.downscale
        intermediate = self.intermediate
        if downscale is not None and min(x.shape[2:]) >= 128:
            w = self.weight * self.w_mul
            w = F.pad(w, [1, 1, 1, 1])
            # in contrast to upscale, this is a mean...
            w = (w[:, :, 1:, 1:] + w[:, :, :-1, 1:] + w[:, :, 1:, :-1] + w[:, :, :-1, :-1]) * 0.25  # avg_pool?
            x = F.conv2d(x, w, stride=2, padding=(w.size(-1) - 1) // 2)
            have_convolution = True
            downscale = None
        elif downscale is not None:
            assert intermediate is None
            intermediate = downscale

        if not have_convolution and intermediate is None:
            return F.conv2d(x, self.weight * self.w_mul, bias, padding=self.kernel_size // 2)
        elif not have_convolution:
            x = F.conv2d(x, self.weight * self.w_mul, None, padding=self.kernel_size // 2)

        if intermediate is not None:
            x = intermediate(x)

        if bias is not None:
            x = x + bias.view(1, -1, 1, 1)
        return x


class NoiseLayer(nn.Module):
    """adds noise. noise is per pixel (constant over channels) with per-channel weight"""

    def __init__(self, channels):
        super().__init__()
        self.weight = nn.Parameter(torch.zeros(channels))
        self.noise = None

    def forward(self, x, noise=None):
        if noise is None and self.noise is None:
            noise = torch.randn(x.size(0), 1, x.size(2), x.size(3), device=x.device, dtype=x.dtype)
        elif noise is None:
            # here is a little trick: if you get all the noise layers and set each
            # modules .noise attribute, you can have pre-defined noise.
            # Very useful for analysis
            noise = self.noise
        x = x + self.weight.view(1, -1, 1, 1) * noise
        return x


class StyleMod(nn.Module):
    def __init__(self, latent_size, channels, use_wscale):
        super(StyleMod, self).__init__()
        self.lin = EqualizedLinear(latent_size,
                                   channels * 2,
                                   gain=1.0, use_wscale=use_wscale)

    def forward(self, x, latent):
        style = self.lin(latent)  # style => [batch_size, n_channels*2]

        shape = [-1, 2, x.size(1)] + (x.dim() - 2) * [1]
        style = style.view(shape)  # [batch_size, 2, n_channels, ...]
        x = x * (style[:, 0] + 1.) + style[:, 1]
        return x


class LayerEpilogue(nn.Module):
    """Things to do at the end of each layer."""

    def __init__(self, channels, dlatent_size, use_wscale,
                 use_noise, use_pixel_norm, use_instance_norm, use_styles, activation_layer):
        super().__init__()

        layers = []
        if use_noise:
            layers.append(('noise', NoiseLayer(channels)))
        layers.append(('activation', activation_layer))
        if use_pixel_norm:
            layers.append(('pixel_norm', PixelNormLayer()))
        if use_instance_norm:
            layers.append(('instance_norm', nn.InstanceNorm2d(channels)))

        self.top_epi = nn.Sequential(OrderedDict(layers))

        if use_styles:
            self.style_mod = StyleMod(dlatent_size, channels, use_wscale=use_wscale)
        else:
            self.style_mod = None

    def forward(self, x, dlatents_in_slice=None):
        x = self.top_epi(x)
        if self.style_mod is not None:
            x = self.style_mod(x, dlatents_in_slice)
        else:
            assert dlatents_in_slice is None
        return x


class BlurLayer(nn.Module):
    def __init__(self, kernel=None, normalize=True, flip=False, stride=1):
        super(BlurLayer, self).__init__()
        if kernel is None:
            kernel = [1, 2, 1]
        kernel = torch.tensor(kernel, dtype=torch.float32)
        kernel = kernel[:, None] * kernel[None, :]
        kernel = kernel[None, None]
        if normalize:
            kernel = kernel / kernel.sum()
        if flip:
            kernel = kernel[:, :, ::-1, ::-1]
        self.register_buffer('kernel', kernel)
        self.stride = stride

    def forward(self, x):
        # expand kernel channels
        kernel = self.kernel.expand(x.size(1), -1, -1, -1)
        x = F.conv2d(
            x,
            kernel,
            stride=self.stride,
            padding=int((self.kernel.size(2) - 1) / 2),
            groups=x.size(1)
        )
        return x


class View(nn.Module):
    def __init__(self, *shape):
        super().__init__()
        self.shape = shape

    def forward(self, x):
        return x.view(x.size(0), *self.shape)


class StddevLayer(nn.Module):
    def __init__(self, group_size=4, num_new_features=1):
        super().__init__()
        self.group_size = group_size
        self.num_new_features = num_new_features

    def forward(self, x):
        b, c, h, w = x.shape
        group_size = min(self.group_size, b)
        y = x.reshape([group_size, -1, self.num_new_features,
                       c // self.num_new_features, h, w])
        y = y - y.mean(0, keepdim=True)
        y = (y ** 2).mean(0, keepdim=True)
        y = (y + 1e-8) ** 0.5
        y = y.mean([3, 4, 5], keepdim=True).squeeze(3)  # don't keep the meaned-out channels
        y = y.expand(group_size, -1, -1, h, w).clone().reshape(b, self.num_new_features, h, w)
        z = torch.cat([x, y], dim=1)
        return z


class Truncation(nn.Module):
    def __init__(self, avg_latent, max_layer=8, threshold=0.7, beta=0.995):
        super().__init__()
        self.max_layer = max_layer
        self.threshold = threshold
        self.beta = beta
        self.register_buffer('avg_latent', avg_latent)

    def update(self, last_avg):
        self.avg_latent.copy_(self.beta * self.avg_latent + (1. - self.beta) * last_avg)

    def forward(self, x):
        assert x.dim() == 3
        interp = torch.lerp(self.avg_latent, x, self.threshold)
        do_trunc = (torch.arange(x.size(1)) < self.max_layer).view(1, -1, 1).to(x.device)
        return torch.where(do_trunc, interp, x)