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gorold
37 lines
1.4 KiB
Python
37 lines
1.4 KiB
Python
from typing import List, Optional
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import math
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import torch
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from torch import nn
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from torch import Tensor
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class GaussianFourierFeatureTransform(nn.Module):
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"""
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https://github.com/ndahlquist/pytorch-fourier-feature-networks
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Given an input of size [..., time, dim], returns a tensor of size [..., n_fourier_feats, time].
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"""
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def __init__(self, input_dim: int, n_fourier_feats: int, scales: List[int]):
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super().__init__()
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self.input_dim = input_dim
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self.n_fourier_feats = n_fourier_feats
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self.scales = scales
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n_scale_feats = n_fourier_feats // (2 * len(scales))
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assert n_scale_feats * 2 * len(scales) == n_fourier_feats, \
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f"n_fourier_feats: {n_fourier_feats} must be divisible by 2 * len(scales) = {2 * len(scales)}"
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B_size = (input_dim, n_scale_feats)
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B = torch.cat([torch.randn(B_size) * scale for scale in scales], dim=1)
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self.register_buffer('B', B)
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def forward(self, x: Tensor) -> Tensor:
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assert x.dim() >= 2, f"Expected 2 or more dimensional input (got {x.dim()}D input)"
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time, dim = x.shape[-2], x.shape[-1]
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assert dim == self.input_dim, \
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f"Expected input to have {self.input_dim} channels (got {dim} channels)"
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x = torch.einsum('... t n, n d -> ... t d', [x, self.B])
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x = 2 * math.pi * x
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return torch.cat([torch.sin(x), torch.cos(x)], dim=-1)
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