Add MobileViT models (w/ ByobNet base). Close #1038.

timm/models/__init__.py

@@ -24,6 +24,7 @@ from .inception_v4 import *
 from .levit import *
 from .mlp_mixer import *
 from .mobilenetv3 import *
+from .mobilevit import *
 from .nasnet import *
 from .nest import *
 from .nfnet import *

timm/models/mobilevit.py

@@ -0,0 +1,248 @@
+""" MobileViT
+
+Paper:
+`MobileViT: Light-weight, General-purpose, and Mobile-friendly Vision Transformer` - https://arxiv.org/abs/2110.02178
+
+MobileVitBlock and checkpoints adapted from https://github.com/apple/ml-cvnets (original copyright below)
+License: https://github.com/apple/ml-cvnets/blob/main/LICENSE (Apple open source)
+
+Rest of code, ByobNet, and Transformer block hacked together by / Copyright 2022, Ross Wightman
+"""
+#
+# For licensing see accompanying LICENSE file.
+# Copyright (C) 2020 Apple Inc. All Rights Reserved.
+#
+import math
+from typing import Union, Callable, Dict, Tuple, Optional
+
+import torch
+from torch import nn
+import torch.nn.functional as F
+
+from .byobnet import register_block, ByoBlockCfg, ByoModelCfg, ByobNet, LayerFn, num_groups
+from .layers import to_2tuple, make_divisible
+from .vision_transformer import Block as TransformerBlock
+from .helpers import build_model_with_cfg
+from .registry import register_model
+
+__all__ = []
+
+
+def _cfg(url='', **kwargs):
+    return {
+        'url': url, 'num_classes': 1000, 'input_size': (3, 256, 256), 'pool_size': (8, 8),
+        'crop_pct': 0.9, 'interpolation': 'bicubic',
+        'mean': (0, 0, 0), 'std': (1, 1, 1),
+        'first_conv': 'stem.conv', 'classifier': 'head.fc',
+        'fixed_input_size': False, 'min_input_size': (3, 256, 256),
+        **kwargs
+    }
+
+
+default_cfgs = {
+    # GPU-Efficient (ResNet) weights
+    'mobilevit_xxs': _cfg(
+        url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-mvit-weights/mobilevit_xxs-ad385b40.pth'),
+    'mobilevit_xs': _cfg(
+        url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-mvit-weights/mobilevit_xs-8fbd6366.pth'),
+    'mobilevit_s': _cfg(
+        url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-mvit-weights/mobilevit_s-38a5a959.pth'),
+}
+
+
+def _inverted_residual_block(d, c, s, br=4.0):
+    # inverted residual is a bottleneck block with bottle_ratio > 1 applied to in_chs, linear output, gs=1 (depthwise)
+    return ByoBlockCfg(
+        type='bottle', d=d, c=c, s=s, gs=1, br=br,
+        block_kwargs=dict(bottle_in=True, linear_out=True))
+
+
+def _mobilevit_block(d, c, s, transformer_dim, transformer_depth, patch_size=4, br=4.0):
+    # inverted residual + mobilevit blocks as per MobileViT network
+    return (
+        _inverted_residual_block(d=d, c=c, s=s, br=br),
+        ByoBlockCfg(
+            type='mobilevit', d=1, c=c, s=1,
+            block_kwargs=dict(
+                transformer_dim=transformer_dim,
+                transformer_depth=transformer_depth,
+                patch_size=patch_size)
+        )
+    )
+
+
+model_cfgs = dict(
+    mobilevit_xxs=ByoModelCfg(
+        blocks=(
+            _inverted_residual_block(d=1, c=16, s=1, br=2.0),
+            _inverted_residual_block(d=3, c=24, s=2, br=2.0),
+            _mobilevit_block(d=1, c=48, s=2, transformer_dim=64, transformer_depth=2, patch_size=2, br=2.0),
+            _mobilevit_block(d=1, c=64, s=2, transformer_dim=80, transformer_depth=4, patch_size=2, br=2.0),
+            _mobilevit_block(d=1, c=80, s=2, transformer_dim=96, transformer_depth=3, patch_size=2, br=2.0),
+        ),
+        stem_chs=16,
+        stem_type='3x3',
+        stem_pool='',
+        downsample='',
+        act_layer='silu',
+        num_features=320,
+    ),
+
+    mobilevit_xs=ByoModelCfg(
+        blocks=(
+            _inverted_residual_block(d=1, c=32, s=1),
+            _inverted_residual_block(d=3, c=48, s=2),
+            _mobilevit_block(d=1, c=64, s=2, transformer_dim=96, transformer_depth=2, patch_size=2),
+            _mobilevit_block(d=1, c=80, s=2, transformer_dim=120, transformer_depth=4, patch_size=2),
+            _mobilevit_block(d=1, c=96, s=2, transformer_dim=144, transformer_depth=3, patch_size=2),
+        ),
+        stem_chs=16,
+        stem_type='3x3',
+        stem_pool='',
+        downsample='',
+        act_layer='silu',
+        num_features=384,
+    ),
+
+    mobilevit_s=ByoModelCfg(
+        blocks=(
+            _inverted_residual_block(d=1, c=32, s=1),
+            _inverted_residual_block(d=3, c=64, s=2),
+            _mobilevit_block(d=1, c=96, s=2, transformer_dim=144, transformer_depth=2, patch_size=2),
+            _mobilevit_block(d=1, c=128, s=2, transformer_dim=192, transformer_depth=4, patch_size=2),
+            _mobilevit_block(d=1, c=160, s=2, transformer_dim=240, transformer_depth=3, patch_size=2),
+        ),
+        stem_chs=16,
+        stem_type='3x3',
+        stem_pool='',
+        downsample='',
+        act_layer='silu',
+        num_features=640,
+    ),
+)
+
+
+class MobileViTBlock(nn.Module):
+    """ MobileViT block
+        Paper: https://arxiv.org/abs/2110.02178?context=cs.LG
+    """
+    def __init__(
+            self,
+            in_chs: int,
+            out_chs: Optional[int] = None,
+            kernel_size: int = 3,
+            stride: int = 1,
+            bottle_ratio: float = 1.0,
+            group_size: Optional[int] = None,
+            dilation: Tuple[int, int] = (1, 1),
+            mlp_ratio: float = 2.0,
+            transformer_dim: Optional[int] = None,
+            transformer_depth: int = 2,
+            patch_size: int = 8,
+            num_heads: int = 4,
+            attn_drop: float = 0.,
+            drop: int = 0.,
+            no_fusion: bool = False,
+            drop_path_rate: float = 0.,
+            layers: LayerFn = None,
+            transformer_norm_layer: Callable = nn.LayerNorm,
+            downsample: str = ''
+    ):
+        super(MobileViTBlock, self).__init__()
+
+        layers = layers or LayerFn()
+        groups = num_groups(group_size, in_chs)
+        out_chs = out_chs or in_chs
+        transformer_dim = transformer_dim or make_divisible(bottle_ratio * in_chs)
+
+        self.conv_kxk = layers.conv_norm_act(
+            in_chs, in_chs, kernel_size=kernel_size,
+            stride=stride, groups=groups, dilation=dilation[0])
+        self.conv_1x1 = nn.Conv2d(in_chs, transformer_dim, kernel_size=1, bias=False)
+
+        self.transformer = nn.Sequential(*[
+            TransformerBlock(
+                transformer_dim, mlp_ratio=mlp_ratio, num_heads=num_heads, qkv_bias=True,
+                attn_drop=attn_drop, drop=drop, drop_path=drop_path_rate,
+                act_layer=layers.act, norm_layer=transformer_norm_layer)
+            for _ in range(transformer_depth)
+        ])
+        self.norm = transformer_norm_layer(transformer_dim)
+
+        self.conv_proj = layers.conv_norm_act(transformer_dim, out_chs, kernel_size=1, stride=1)
+
+        if no_fusion:
+            self.conv_fusion = None
+        else:
+            self.conv_fusion = layers.conv_norm_act(in_chs + out_chs, out_chs, kernel_size=kernel_size, stride=1)
+
+        self.patch_size = to_2tuple(patch_size)
+        self.patch_area = self.patch_size[0] * self.patch_size[1]
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        shortcut = x
+
+        # Local representation
+        x = self.conv_kxk(x)
+        x = self.conv_1x1(x)
+
+        # Unfold (feature map -> patches)
+        patch_h, patch_w = self.patch_size
+        B, C, H, W = x.shape
+        new_h, new_w = int(math.ceil(H / patch_h) * patch_h), int(math.ceil(W / patch_w) * patch_w)
+        num_patch_h, num_patch_w = new_h // patch_h, new_w // patch_w  # n_h, n_w
+        num_patches = num_patch_h * num_patch_w  # N
+        interpolate = False
+        if new_h != H or new_w != W:
+            # Note: Padding can be done, but then it needs to be handled in attention function.
+            x = F.interpolate(x, size=(new_h, new_w), mode="bilinear", align_corners=False)
+            interpolate = True
+
+        # [B, C, H, W] --> [B * C * n_h, n_w, p_h, p_w]
+        x = x.reshape(B * C * num_patch_h, patch_h, num_patch_w, patch_w).transpose(1, 2)
+        # [B * C * n_h, n_w, p_h, p_w] --> [BP, N, C] where P = p_h * p_w and N = n_h * n_w
+        x = x.reshape(B, C, num_patches, self.patch_area).transpose(1, 3).reshape(B * self.patch_area, num_patches, -1)
+
+        # Global representations
+        x = self.transformer(x)
+        x = self.norm(x)
+
+        # Fold (patch -> feature map)
+        # [B, P, N, C] --> [B*C*n_h, n_w, p_h, p_w]
+        x = x.contiguous().view(B, self.patch_area, num_patches, -1)
+        x = x.transpose(1, 3).reshape(B * C * num_patch_h, num_patch_w, patch_h, patch_w)
+        # [B*C*n_h, n_w, p_h, p_w] --> [B*C*n_h, p_h, n_w, p_w] --> [B, C, H, W]
+        x = x.transpose(1, 2).reshape(B, C, num_patch_h * patch_h, num_patch_w * patch_w)
+        if interpolate:
+            x = F.interpolate(x, size=(H, W), mode="bilinear", align_corners=False)
+
+        x = self.conv_proj(x)
+        if self.conv_fusion is not None:
+            x = self.conv_fusion(torch.cat((shortcut, x), dim=1))
+        return x
+
+
+register_block('mobilevit', MobileViTBlock)
+
+
+def _create_mobilevit(variant, cfg_variant=None, pretrained=False, **kwargs):
+    return build_model_with_cfg(
+        ByobNet, variant, pretrained,
+        model_cfg=model_cfgs[variant] if not cfg_variant else model_cfgs[cfg_variant],
+        feature_cfg=dict(flatten_sequential=True),
+        **kwargs)
+
+
+@register_model
+def mobilevit_xxs(pretrained=False, **kwargs):
+    return _create_mobilevit('mobilevit_xxs', pretrained=pretrained, **kwargs)
+
+
+@register_model
+def mobilevit_xs(pretrained=False, **kwargs):
+    return _create_mobilevit('mobilevit_xs', pretrained=pretrained, **kwargs)
+
+
+@register_model
+def mobilevit_s(pretrained=False, **kwargs):
+    return _create_mobilevit('mobilevit_s', pretrained=pretrained, **kwargs)