109 lines
3.7 KiB
Python
109 lines
3.7 KiB
Python
""" MLP module w/ dropout and configurable activation layer
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Hacked together by / Copyright 2020 Ross Wightman
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"""
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from torch import nn as nn
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class Mlp(nn.Module):
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""" MLP as used in Vision Transformer, MLP-Mixer and related networks
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"""
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def __init__(self, in_features, hidden_features=None, out_features=None, act_layer=nn.GELU, drop=0.):
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super().__init__()
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out_features = out_features or in_features
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hidden_features = hidden_features or in_features
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self.fc1 = nn.Linear(in_features, hidden_features)
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self.act = act_layer()
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self.fc2 = nn.Linear(hidden_features, out_features)
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self.drop = nn.Dropout(drop)
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def forward(self, x):
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x = self.fc1(x)
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x = self.act(x)
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x = self.drop(x)
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x = self.fc2(x)
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x = self.drop(x)
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return x
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class GluMlp(nn.Module):
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""" MLP w/ GLU style gating
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See: https://arxiv.org/abs/1612.08083, https://arxiv.org/abs/2002.05202
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"""
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def __init__(self, in_features, hidden_features=None, out_features=None, act_layer=nn.Sigmoid, drop=0.):
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super().__init__()
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out_features = out_features or in_features
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hidden_features = hidden_features or in_features
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assert hidden_features % 2 == 0
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self.fc1 = nn.Linear(in_features, hidden_features)
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self.act = act_layer()
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self.fc2 = nn.Linear(hidden_features // 2, out_features)
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self.drop = nn.Dropout(drop)
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def init_weights(self):
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# override init of fc1 w/ gate portion set to weight near zero, bias=1
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fc1_mid = self.fc1.bias.shape[0] // 2
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nn.init.ones_(self.fc1.bias[fc1_mid:])
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nn.init.normal_(self.fc1.weight[fc1_mid:], std=1e-6)
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def forward(self, x):
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x = self.fc1(x)
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x, gates = x.chunk(2, dim=-1)
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x = x * self.act(gates)
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x = self.drop(x)
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x = self.fc2(x)
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x = self.drop(x)
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return x
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class GatedMlp(nn.Module):
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""" MLP as used in gMLP
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"""
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def __init__(self, in_features, hidden_features=None, out_features=None, act_layer=nn.GELU,
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gate_layer=None, drop=0.):
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super().__init__()
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out_features = out_features or in_features
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hidden_features = hidden_features or in_features
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self.fc1 = nn.Linear(in_features, hidden_features)
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self.act = act_layer()
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if gate_layer is not None:
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assert hidden_features % 2 == 0
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self.gate = gate_layer(hidden_features)
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hidden_features = hidden_features // 2 # FIXME base reduction on gate property?
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else:
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self.gate = nn.Identity()
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self.fc2 = nn.Linear(hidden_features, out_features)
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self.drop = nn.Dropout(drop)
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def forward(self, x):
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x = self.fc1(x)
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x = self.act(x)
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x = self.drop(x)
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x = self.gate(x)
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x = self.fc2(x)
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x = self.drop(x)
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return x
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class ConvMlp(nn.Module):
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""" MLP using 1x1 convs that keeps spatial dims
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"""
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def __init__(
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self, in_features, hidden_features=None, out_features=None, act_layer=nn.ReLU, norm_layer=None, drop=0.):
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super().__init__()
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out_features = out_features or in_features
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hidden_features = hidden_features or in_features
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self.fc1 = nn.Conv2d(in_features, hidden_features, kernel_size=1, bias=True)
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self.norm = norm_layer(hidden_features) if norm_layer else nn.Identity()
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self.act = act_layer()
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self.fc2 = nn.Conv2d(hidden_features, out_features, kernel_size=1, bias=True)
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self.drop = nn.Dropout(drop)
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def forward(self, x):
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x = self.fc1(x)
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x = self.norm(x)
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x = self.act(x)
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x = self.drop(x)
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x = self.fc2(x)
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return x
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