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""" |
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Various utilities for neural networks. |
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""" |
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import math |
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import torch as th |
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import torch.nn as nn |
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class SiLU(nn.Module): |
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def forward(self, x): |
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return x * th.sigmoid(x) |
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class GroupNorm32(nn.GroupNorm): |
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def forward(self, x): |
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return super().forward(x.float()).type(x.dtype) |
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def conv_nd(dims, *args, **kwargs): |
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""" |
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Create a 1D, 2D, or 3D convolution module. |
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""" |
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if dims == 1: |
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return nn.Conv1d(*args, **kwargs) |
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elif dims == 2: |
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return nn.Conv2d(*args, **kwargs) |
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elif dims == 3: |
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return nn.Conv3d(*args, **kwargs) |
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raise ValueError(f"unsupported dimensions: {dims}") |
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def linear(*args, **kwargs): |
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""" |
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Create a linear module. |
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""" |
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return nn.Linear(*args, **kwargs) |
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def avg_pool_nd(dims, *args, **kwargs): |
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""" |
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Create a 1D, 2D, or 3D average pooling module. |
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""" |
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if dims == 1: |
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return nn.AvgPool1d(*args, **kwargs) |
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elif dims == 2: |
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return nn.AvgPool2d(*args, **kwargs) |
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elif dims == 3: |
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return nn.AvgPool3d(*args, **kwargs) |
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raise ValueError(f"unsupported dimensions: {dims}") |
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def update_ema(target_params, source_params, rate=0.99): |
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""" |
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Update target parameters to be closer to those of source parameters using |
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an exponential moving average. |
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:param target_params: the target parameter sequence. |
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:param source_params: the source parameter sequence. |
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:param rate: the EMA rate (closer to 1 means slower). |
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""" |
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for targ, src in zip(target_params, source_params): |
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targ.detach().mul_(rate).add_(src, alpha=1 - rate) |
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def zero_module(module): |
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""" |
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Zero out the parameters of a module and return it. |
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""" |
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for p in module.parameters(): |
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p.detach().zero_() |
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return module |
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def scale_module(module, scale): |
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""" |
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Scale the parameters of a module and return it. |
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""" |
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for p in module.parameters(): |
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p.detach().mul_(scale) |
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return module |
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def mean_flat(tensor): |
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""" |
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Take the mean over all non-batch dimensions. |
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""" |
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return tensor.mean(dim=list(range(1, len(tensor.shape)))) |
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def normalization(channels): |
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""" |
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Make a standard normalization layer. |
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:param channels: number of input channels. |
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:return: an nn.Module for normalization. |
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""" |
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return GroupNorm32(32, channels) |
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def timestep_embedding(timesteps, dim, max_period=10000): |
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""" |
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Create sinusoidal timestep embeddings. |
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:param timesteps: a 1-D Tensor of N indices, one per batch element. |
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These may be fractional. |
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:param dim: the dimension of the output. |
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:param max_period: controls the minimum frequency of the embeddings. |
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:return: an [N x dim] Tensor of positional embeddings. |
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""" |
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half = dim // 2 |
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freqs = th.exp( |
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-math.log(max_period) * th.arange(start=0, end=half, dtype=th.float32) / half |
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).to(device=timesteps.device) |
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args = timesteps[:, None].float() * freqs[None] |
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embedding = th.cat([th.cos(args), th.sin(args)], dim=-1) |
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if dim % 2: |
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embedding = th.cat([embedding, th.zeros_like(embedding[:, :1])], dim=-1) |
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return embedding |
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