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Add layer scale and parallel blocks to vision_transformer

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pull/1190/head
Ross Wightman 3 years ago
parent c42be74621
commit 1618527098
1 changed files with 102 additions and 9 deletions
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111
timm/models/vision_transformer.py
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@ -170,6 +170,11 @@ default_cfgs = {
'/vit_base_patch16_224_1k_miil_84_4.pth',
mean=(0, 0, 0), std=(1, 1, 1), crop_pct=0.875, interpolation='bilinear',
),
# experimental
'vit_small_patch16_36x1_224': _cfg(url=''),
'vit_small_patch16_18x2_224': _cfg(url=''),
'vit_base_patch16_18x2_224': _cfg(url=''),
}
@ -201,28 +206,81 @@ class Attention(nn.Module):
return x
class LayerScale(nn.Module):
def __init__(self, dim, init_values=1e-5, inplace=False):
super().__init__()
self.inplace = inplace
self.gamma = nn.Parameter(init_values * torch.ones(dim))
def forward(self, x):
return x.mul_(self.gamma) if self.inplace else x * self.gamma
class Block(nn.Module):
def __init__(
self, dim, num_heads, mlp_ratio=4., qkv_bias=False, drop=0., attn_drop=0.,
self, dim, num_heads, mlp_ratio=4., qkv_bias=False, drop=0., attn_drop=0., init_values=None,
drop_path=0., act_layer=nn.GELU, norm_layer=nn.LayerNorm):
super().__init__()
self.norm1 = norm_layer(dim)
self.attn = Attention(dim, num_heads=num_heads, qkv_bias=qkv_bias, attn_drop=attn_drop, proj_drop=drop)
self.ls1 = LayerScale(dim, init_values=init_values) if init_values else nn.Identity()
# NOTE: drop path for stochastic depth, we shall see if this is better than dropout here
self.drop_path1 = DropPath(drop_path) if drop_path > 0. else nn.Identity()
self.norm2 = norm_layer(dim)
mlp_hidden_dim = int(dim * mlp_ratio)
self.mlp = Mlp(in_features=dim, hidden_features=mlp_hidden_dim, act_layer=act_layer, drop=drop)
self.ls2 = LayerScale(dim, init_values=init_values) if init_values else nn.Identity()
self.drop_path2 = DropPath(drop_path) if drop_path > 0. else nn.Identity()
def forward(self, x):
x = x + self.drop_path1(self.attn(self.norm1(x)))
x = x + self.drop_path2(self.mlp(self.norm2(x)))
x = x + self.drop_path1(self.ls1(self.attn(self.norm1(x))))
x = x + self.drop_path2(self.ls2(self.mlp(self.norm2(x))))
return x
class ParallelBlock(nn.Module):
def __init__(
self, dim, num_heads, num_parallel=2, mlp_ratio=4., qkv_bias=False, init_values=None,
drop=0., attn_drop=0., drop_path=0., act_layer=nn.GELU, norm_layer=nn.LayerNorm):
super().__init__()
self.num_parallel = num_parallel
self.attns = nn.ModuleList()
self.ffns = nn.ModuleList()
for _ in range(num_parallel):
self.attns.append(nn.Sequential(OrderedDict([
('norm', norm_layer(dim)),
('attn', Attention(dim, num_heads=num_heads, qkv_bias=qkv_bias, attn_drop=attn_drop, proj_drop=drop)),
('ls', LayerScale(dim, init_values=init_values) if init_values else nn.Identity()),
('drop_path', DropPath(drop_path) if drop_path > 0. else nn.Identity())
])))
self.ffns.append(nn.Sequential(OrderedDict([
('norm', norm_layer(dim)),
('mlp', Mlp(dim, hidden_features=int(dim * mlp_ratio), act_layer=act_layer, drop=drop)),
('ls', LayerScale(dim, init_values=init_values) if init_values else nn.Identity()),
('drop_path', DropPath(drop_path) if drop_path > 0. else nn.Identity())
])))
def _forward_jit(self, x):
x = x + torch.stack([attn(x) for attn in self.attns]).sum(dim=0)
x = x + torch.stack([ffn(x) for ffn in self.ffns]).sum(dim=0)
return x
@torch.jit.ignore
def _forward(self, x):
x = x + sum(attn(x) for attn in self.attns)
x = x + sum(ffn(x) for ffn in self.ffns)
return x
def forward(self, x):
if torch.jit.is_scripting() or torch.jit.is_tracing():
return self._forward_jit(x)
else:
return self._forward(x)
class VisionTransformer(nn.Module):
""" Vision Transformer
@ -233,8 +291,8 @@ class VisionTransformer(nn.Module):
def __init__(
self, img_size=224, patch_size=16, in_chans=3, num_classes=1000, global_pool='token',
embed_dim=768, depth=12, num_heads=12, mlp_ratio=4., qkv_bias=True, representation_size=None,
drop_rate=0., attn_drop_rate=0., drop_path_rate=0., weight_init='',
embed_layer=PatchEmbed, norm_layer=None, act_layer=None):
drop_rate=0., attn_drop_rate=0., drop_path_rate=0., weight_init='', init_values=None,
embed_layer=PatchEmbed, norm_layer=None, act_layer=None, block_fn=Block):
"""
Args:
img_size (int, tuple): input image size
@ -248,10 +306,11 @@ class VisionTransformer(nn.Module):
mlp_ratio (int): ratio of mlp hidden dim to embedding dim
qkv_bias (bool): enable bias for qkv if True
representation_size (Optional[int]): enable and set representation layer (pre-logits) to this value if set
weight_init: (str): weight init scheme
drop_rate (float): dropout rate
attn_drop_rate (float): attention dropout rate
drop_path_rate (float): stochastic depth rate
weight_init: (str): weight init scheme
init_values: (float): layer-scale init values
embed_layer (nn.Module): patch embedding layer
norm_layer: (nn.Module): normalization layer
act_layer: (nn.Module): MLP activation layer
@ -277,9 +336,9 @@ class VisionTransformer(nn.Module):
dpr = [x.item() for x in torch.linspace(0, drop_path_rate, depth)] # stochastic depth decay rule
self.blocks = nn.Sequential(*[
Block(
dim=embed_dim, num_heads=num_heads, mlp_ratio=mlp_ratio, qkv_bias=qkv_bias, drop=drop_rate,
attn_drop=attn_drop_rate, drop_path=dpr[i], norm_layer=norm_layer, act_layer=act_layer)
block_fn(
dim=embed_dim, num_heads=num_heads, mlp_ratio=mlp_ratio, qkv_bias=qkv_bias, init_values=init_values,
drop=drop_rate, attn_drop=attn_drop_rate, drop_path=dpr[i], norm_layer=norm_layer, act_layer=act_layer)
for i in range(depth)])
use_fc_norm = self.global_pool == 'avg'
self.norm = norm_layer(embed_dim) if not use_fc_norm else nn.Identity()
@ -941,3 +1000,37 @@ def vit_base_patch16_224_miil(pretrained=False, **kwargs):
model_kwargs = dict(patch_size=16, embed_dim=768, depth=12, num_heads=12, qkv_bias=False, **kwargs)
model = _create_vision_transformer('vit_base_patch16_224_miil', pretrained=pretrained, **model_kwargs)
return model
@register_model
def vit_small_patch16_36x1_224(pretrained=False, **kwargs):
""" ViT-Base w/ LayerScale + 36 x 1 (36 block serial) config. Experimental, may remove.
Based on `Three things everyone should know about Vision Transformers` - https://arxiv.org/abs/2203.09795
Paper focuses on 24x2 + 48x1 for 'Small' width but those are extremely slow.
"""
model_kwargs = dict(patch_size=16, embed_dim=384, depth=36, num_heads=6, init_values=1e-5, **kwargs)
model = _create_vision_transformer('vit_small_patch16_36x1_224', pretrained=pretrained, **model_kwargs)
return model
@register_model
def vit_small_patch16_18x2_224(pretrained=False, **kwargs):
""" ViT-Small w/ LayerScale + 18 x 2 (36 block parallel) config. Experimental, may remove.
Based on `Three things everyone should know about Vision Transformers` - https://arxiv.org/abs/2203.09795
Paper focuses on 24x2 + 48x1 for 'Small' width but those are extremely slow.
"""
model_kwargs = dict(
patch_size=16, embed_dim=384, depth=18, num_heads=6, init_values=1e-5, block_fn=ParallelBlock, **kwargs)
model = _create_vision_transformer('vit_small_patch16_18x2_224', pretrained=pretrained, **model_kwargs)
return model
@register_model
def vit_base_patch16_18x2_224(pretrained=False, **kwargs):
""" ViT-Base w/ LayerScale + 18 x 2 (36 block parallel) config. Experimental, may remove.
Based on `Three things everyone should know about Vision Transformers` - https://arxiv.org/abs/2203.09795
"""
model_kwargs = dict(
patch_size=16, embed_dim=768, depth=18, num_heads=12, init_values=1e-5, block_fn=ParallelBlock, **kwargs)
model = _create_vision_transformer('vit_base_patch16_18x2_224', pretrained=pretrained, **model_kwargs)
return model

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