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| import torch | |
| from torch import nn | |
| from torch.nn import functional as F | |
| from attention import SelfAttention, CrossAttention | |
| class TimeEmbedding(nn.Module): | |
| def __init__(self, n_embd): | |
| super().__init__() | |
| self.linear_1 = nn.Linear(n_embd, 4 * n_embd) | |
| self.linear_2 = nn.Linear(4 * n_embd, 4 * n_embd) | |
| def forward(self, x): | |
| x = self.linear_1(x) | |
| x = F.silu(x) | |
| x = self.linear_2(x) | |
| return x | |
| class UNET_ResidualBlock(nn.Module): | |
| def __init__(self, in_channels, out_channels, n_time=1280): | |
| super().__init__() | |
| self.groupnorm_feature = nn.GroupNorm(32, in_channels) | |
| self.conv_feature = nn.Conv2d(in_channels, out_channels, kernel_size=3, padding=1) | |
| self.linear_time = nn.Linear(n_time, out_channels) | |
| self.groupnorm_merged = nn.GroupNorm(32, out_channels) | |
| self.conv_merged = nn.Conv2d(out_channels, out_channels, kernel_size=3, padding=1) | |
| if in_channels == out_channels: | |
| self.residual_layer = nn.Identity() | |
| else: | |
| self.residual_layer = nn.Conv2d(in_channels, out_channels, kernel_size=1, padding=0) | |
| def forward(self, feature, time): | |
| residue = feature | |
| feature = self.groupnorm_feature(feature) | |
| feature = F.silu(feature) | |
| feature = self.conv_feature(feature) | |
| time = F.silu(time) | |
| time = self.linear_time(time) | |
| merged = feature + time.unsqueeze(-1).unsqueeze(-1) | |
| merged = self.groupnorm_merged(merged) | |
| merged = F.silu(merged) | |
| merged = self.conv_merged(merged) | |
| return merged + self.residual_layer(residue) | |
| class UNET_AttentionBlock(nn.Module): | |
| def __init__(self, n_head: int, n_embd: int, d_context=768): | |
| super().__init__() | |
| channels = n_head * n_embd | |
| self.groupnorm = nn.GroupNorm(32, channels, eps=1e-6) | |
| self.conv_input = nn.Conv2d(channels, channels, kernel_size=1, padding=0) | |
| self.layernorm_1 = nn.LayerNorm(channels) | |
| self.attention_1 = SelfAttention(n_head, channels, in_proj_bias=False) | |
| self.layernorm_2 = nn.LayerNorm(channels) | |
| self.attention_2 = CrossAttention(n_head, channels, d_context, in_proj_bias=False) | |
| self.layernorm_3 = nn.LayerNorm(channels) | |
| self.linear_geglu_1 = nn.Linear(channels, 4 * channels * 2) | |
| self.linear_geglu_2 = nn.Linear(4 * channels, channels) | |
| self.conv_output = nn.Conv2d(channels, channels, kernel_size=1, padding=0) | |
| def forward(self, x, context): | |
| residue_long = x | |
| x = self.groupnorm(x) | |
| x = self.conv_input(x) | |
| n, c, h, w = x.shape | |
| x = x.view((n, c, h * w)) | |
| x = x.transpose(-1, -2) | |
| residue_short = x | |
| x = self.layernorm_1(x) | |
| x = self.attention_1(x) | |
| x += residue_short | |
| residue_short = x | |
| x = self.layernorm_2(x) | |
| x = self.attention_2(x, context) | |
| x += residue_short | |
| residue_short = x | |
| x = self.layernorm_3(x) | |
| # GeGLU as implemented in the original code: https://github.com/CompVis/stable-diffusion/blob/21f890f9da3cfbeaba8e2ac3c425ee9e998d5229/ldm/modules/attention.py#L37C10-L37C10 | |
| x, gate = self.linear_geglu_1(x).chunk(2, dim=-1) | |
| x = x * F.gelu(gate) | |
| x = self.linear_geglu_2(x) | |
| x += residue_short | |
| x = x.transpose(-1, -2) | |
| x = x.view((n, c, h, w)) | |
| return self.conv_output(x) + residue_long | |
| class Upsample(nn.Module): | |
| def __init__(self, channels): | |
| super().__init__() | |
| self.conv = nn.Conv2d(channels, channels, kernel_size=3, padding=1) | |
| def forward(self, x): | |
| x = F.interpolate(x, scale_factor=2, mode='nearest') | |
| return self.conv(x) | |
| class SwitchSequential(nn.Sequential): | |
| def forward(self, x, context, time): | |
| for layer in self: | |
| if isinstance(layer, UNET_AttentionBlock): | |
| x = layer(x, context) | |
| elif isinstance(layer, UNET_ResidualBlock): | |
| x = layer(x, time) | |
| else: | |
| x = layer(x) | |
| return x | |
| class UNET(nn.Module): | |
| def __init__(self): | |
| super().__init__() | |
| self.encoders = nn.ModuleList([ | |
| SwitchSequential(nn.Conv2d(4, 320, kernel_size=3, padding=1)), | |
| SwitchSequential(UNET_ResidualBlock(320, 320), UNET_AttentionBlock(8, 40)), | |
| SwitchSequential(UNET_ResidualBlock(320, 320), UNET_AttentionBlock(8, 40)), | |
| SwitchSequential(nn.Conv2d(320, 320, kernel_size=3, stride=2, padding=1)), | |
| SwitchSequential(UNET_ResidualBlock(320, 640), UNET_AttentionBlock(8, 80)), | |
| SwitchSequential(UNET_ResidualBlock(640, 640), UNET_AttentionBlock(8, 80)), | |
| SwitchSequential(nn.Conv2d(640, 640, kernel_size=3, stride=2, padding=1)), | |
| SwitchSequential(UNET_ResidualBlock(640, 1280), UNET_AttentionBlock(8, 160)), | |
| SwitchSequential(UNET_ResidualBlock(1280, 1280), UNET_AttentionBlock(8, 160)), | |
| SwitchSequential(nn.Conv2d(1280, 1280, kernel_size=3, stride=2, padding=1)), | |
| SwitchSequential(UNET_ResidualBlock(1280, 1280)), | |
| SwitchSequential(UNET_ResidualBlock(1280, 1280)), | |
| ]) | |
| self.bottleneck = SwitchSequential( | |
| UNET_ResidualBlock(1280, 1280), | |
| UNET_AttentionBlock(8, 160), | |
| UNET_ResidualBlock(1280, 1280), | |
| ) | |
| self.decoders = nn.ModuleList([ | |
| SwitchSequential(UNET_ResidualBlock(2560, 1280)), | |
| SwitchSequential(UNET_ResidualBlock(2560, 1280)), | |
| SwitchSequential(UNET_ResidualBlock(2560, 1280), Upsample(1280)), | |
| SwitchSequential(UNET_ResidualBlock(2560, 1280), UNET_AttentionBlock(8, 160)), | |
| SwitchSequential(UNET_ResidualBlock(2560, 1280), UNET_AttentionBlock(8, 160)), | |
| SwitchSequential(UNET_ResidualBlock(1920, 1280), UNET_AttentionBlock(8, 160), Upsample(1280)), | |
| SwitchSequential(UNET_ResidualBlock(1920, 640), UNET_AttentionBlock(8, 80)), | |
| SwitchSequential(UNET_ResidualBlock(1280, 640), UNET_AttentionBlock(8, 80)), | |
| SwitchSequential(UNET_ResidualBlock(960, 640), UNET_AttentionBlock(8, 80), Upsample(640)), | |
| SwitchSequential(UNET_ResidualBlock(960, 320), UNET_AttentionBlock(8, 40)), | |
| SwitchSequential(UNET_ResidualBlock(640, 320), UNET_AttentionBlock(8, 40)), | |
| SwitchSequential(UNET_ResidualBlock(640, 320), UNET_AttentionBlock(8, 40)), | |
| ]) | |
| def forward(self, x, context, time): | |
| skip_connections = [] | |
| for layers in self.encoders: | |
| x = layers(x, context, time) | |
| skip_connections.append(x) | |
| x = self.bottleneck(x, context, time) | |
| for layers in self.decoders: | |
| x = torch.cat((x, skip_connections.pop()), dim=1) | |
| x = layers(x, context, time) | |
| return x | |
| class UNET_OutputLayer(nn.Module): | |
| def __init__(self, in_channels, out_channels): | |
| super().__init__() | |
| self.groupnorm = nn.GroupNorm(32, in_channels) | |
| self.conv = nn.Conv2d(in_channels, out_channels, kernel_size=3, padding=1) | |
| def forward(self, x): | |
| x = self.groupnorm(x) | |
| x = F.silu(x) | |
| x = self.conv(x) | |
| return x | |
| class Diffusion(nn.Module): | |
| def __init__(self): | |
| super().__init__() | |
| self.time_embedding = TimeEmbedding(320) | |
| self.unet = UNET() | |
| self.final = UNET_OutputLayer(320, 4) | |
| def forward(self, latent, context, time): | |
| time = self.time_embedding(time) | |
| output = self.unet(latent, context, time) | |
| output = self.final(output) | |
| return output |