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+# --------------------------------------------------------
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+# Swin Transformer
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+# Copyright (c) 2021 Microsoft
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+# Licensed under The MIT License [see LICENSE for details]
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+# Written by Ze Liu
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+# --------------------------------------------------------
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+
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+import torch
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+import torch.nn as nn
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+import torch.utils.checkpoint as checkpoint
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+from timm.models.layers import DropPath, to_2tuple, trunc_normal_
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+
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+try:
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+ import os, sys
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+
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+ kernel_path = os.path.abspath(os.path.join('..'))
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+ sys.path.append(kernel_path)
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+ from kernels.window_process.window_process import WindowProcess, WindowProcessReverse
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+
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+except:
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+ WindowProcess = None
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+ WindowProcessReverse = None
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+ print("[Warning] Fused window process have not been installed. Please refer to get_started.md for installation.")
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+
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+
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+class Mlp(nn.Module):
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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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+
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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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+
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+
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+def window_partition(x, window_size):
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+ """
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+ Args:
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+ x: (B, H, W, C)
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+ window_size (int): window size
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+
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+ Returns:
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+ windows: (num_windows*B, window_size, window_size, C)
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+ """
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+ B, H, W, C = x.shape
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+ x = x.view(B, H // window_size, window_size, W // window_size, window_size, C)
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+ windows = x.permute(0, 1, 3, 2, 4, 5).contiguous().view(-1, window_size, window_size, C)
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+ return windows
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+
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+
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+def window_reverse(windows, window_size, H, W):
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+ """
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+ Args:
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+ windows: (num_windows*B, window_size, window_size, C)
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+ window_size (int): Window size
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+ H (int): Height of image
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+ W (int): Width of image
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+
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+ Returns:
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+ x: (B, H, W, C)
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+ """
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+ B = int(windows.shape[0] / (H * W / window_size / window_size))
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+ x = windows.view(B, H // window_size, W // window_size, window_size, window_size, -1)
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+ x = x.permute(0, 1, 3, 2, 4, 5).contiguous().view(B, H, W, -1)
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+ return x
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+
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+
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+class WindowAttention(nn.Module):
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+ r""" Window based multi-head self attention (W-MSA) module with relative position bias.
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+ It supports both of shifted and non-shifted window.
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+
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+ Args:
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+ dim (int): Number of input channels.
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+ window_size (tuple[int]): The height and width of the window.
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+ num_heads (int): Number of attention heads.
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+ qkv_bias (bool, optional): If True, add a learnable bias to query, key, value. Default: True
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+ qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set
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+ attn_drop (float, optional): Dropout ratio of attention weight. Default: 0.0
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+ proj_drop (float, optional): Dropout ratio of output. Default: 0.0
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+ """
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+
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+ def __init__(self, dim, window_size, num_heads, qkv_bias=True, qk_scale=None, attn_drop=0., proj_drop=0.):
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+
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+ super().__init__()
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+ self.dim = dim
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+ self.window_size = window_size # Wh, Ww
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+ self.num_heads = num_heads
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+ head_dim = dim // num_heads
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+ self.scale = qk_scale or head_dim ** -0.5
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+
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+ # define a parameter table of relative position bias
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+ self.relative_position_bias_table = nn.Parameter(
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+ torch.zeros((2 * window_size[0] - 1) * (2 * window_size[1] - 1), num_heads)) # 2*Wh-1 * 2*Ww-1, nH
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+
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+ # get pair-wise relative position index for each token inside the window
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+ coords_h = torch.arange(self.window_size[0])
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+ coords_w = torch.arange(self.window_size[1])
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+ coords = torch.stack(torch.meshgrid([coords_h, coords_w])) # 2, Wh, Ww
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+ coords_flatten = torch.flatten(coords, 1) # 2, Wh*Ww
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+ relative_coords = coords_flatten[:, :, None] - coords_flatten[:, None, :] # 2, Wh*Ww, Wh*Ww
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+ relative_coords = relative_coords.permute(1, 2, 0).contiguous() # Wh*Ww, Wh*Ww, 2
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+ relative_coords[:, :, 0] += self.window_size[0] - 1 # shift to start from 0
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+ relative_coords[:, :, 1] += self.window_size[1] - 1
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+ relative_coords[:, :, 0] *= 2 * self.window_size[1] - 1
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+ relative_position_index = relative_coords.sum(-1) # Wh*Ww, Wh*Ww
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+ self.register_buffer("relative_position_index", relative_position_index)
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+
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+ self.qkv = nn.Linear(dim, dim * 3, bias=qkv_bias)
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+ self.attn_drop = nn.Dropout(attn_drop)
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+ self.proj = nn.Linear(dim, dim)
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+ self.proj_drop = nn.Dropout(proj_drop)
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+
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+ trunc_normal_(self.relative_position_bias_table, std=.02)
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+ self.softmax = nn.Softmax(dim=-1)
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+
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+ def forward(self, x, mask=None):
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+ """
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+ Args:
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+ x: input features with shape of (num_windows*B, N, C)
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+ mask: (0/-inf) mask with shape of (num_windows, Wh*Ww, Wh*Ww) or None
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+ """
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+ B_, N, C = x.shape
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+ qkv = self.qkv(x).reshape(B_, N, 3, self.num_heads, C // self.num_heads).permute(2, 0, 3, 1, 4)
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+ q, k, v = qkv[0], qkv[1], qkv[2] # make torchscript happy (cannot use tensor as tuple)
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+
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+ q = q * self.scale
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+ attn = (q @ k.transpose(-2, -1))
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+
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+ relative_position_bias = self.relative_position_bias_table[self.relative_position_index.view(-1)].view(
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+ self.window_size[0] * self.window_size[1], self.window_size[0] * self.window_size[1], -1) # Wh*Ww,Wh*Ww,nH
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+ relative_position_bias = relative_position_bias.permute(2, 0, 1).contiguous() # nH, Wh*Ww, Wh*Ww
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+ attn = attn + relative_position_bias.unsqueeze(0)
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+
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+ if mask is not None:
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+ nW = mask.shape[0]
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+ attn = attn.view(B_ // nW, nW, self.num_heads, N, N) + mask.unsqueeze(1).unsqueeze(0)
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+ attn = attn.view(-1, self.num_heads, N, N)
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+ attn = self.softmax(attn)
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+ else:
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+ attn = self.softmax(attn)
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+
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+ attn = self.attn_drop(attn)
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+
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+ x = (attn @ v).transpose(1, 2).reshape(B_, N, C)
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+ x = self.proj(x)
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+ x = self.proj_drop(x)
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+ return x
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+
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+ def extra_repr(self) -> str:
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+ return f'dim={self.dim}, window_size={self.window_size}, num_heads={self.num_heads}'
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+
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+ def flops(self, N):
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+ # calculate flops for 1 window with token length of N
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+ flops = 0
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+ # qkv = self.qkv(x)
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+ flops += N * self.dim * 3 * self.dim
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+ # attn = (q @ k.transpose(-2, -1))
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+ flops += self.num_heads * N * (self.dim // self.num_heads) * N
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+ # x = (attn @ v)
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+ flops += self.num_heads * N * N * (self.dim // self.num_heads)
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+ # x = self.proj(x)
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+ flops += N * self.dim * self.dim
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+ return flops
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+
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+
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+class SwinTransformerBlock(nn.Module):
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+ r""" Swin Transformer Block.
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+
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+ Args:
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+ dim (int): Number of input channels.
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+ input_resolution (tuple[int]): Input resulotion.
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+ num_heads (int): Number of attention heads.
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+ window_size (int): Window size.
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+ shift_size (int): Shift size for SW-MSA.
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+ mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
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+ qkv_bias (bool, optional): If True, add a learnable bias to query, key, value. Default: True
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+ qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set.
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+ drop (float, optional): Dropout rate. Default: 0.0
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+ attn_drop (float, optional): Attention dropout rate. Default: 0.0
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+ drop_path (float, optional): Stochastic depth rate. Default: 0.0
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+ act_layer (nn.Module, optional): Activation layer. Default: nn.GELU
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+ norm_layer (nn.Module, optional): Normalization layer. Default: nn.LayerNorm
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+ fused_window_process (bool, optional): If True, use one kernel to fused window shift & window partition for acceleration, similar for the reversed part. Default: False
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+ """
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+
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+ def __init__(self, dim, input_resolution, num_heads, window_size=7, shift_size=0,
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+ mlp_ratio=4., qkv_bias=True, qk_scale=None, drop=0., attn_drop=0., drop_path=0.,
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+ act_layer=nn.GELU, norm_layer=nn.LayerNorm,
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+ fused_window_process=False):
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+ super().__init__()
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+ self.dim = dim
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+ self.input_resolution = input_resolution
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+ self.num_heads = num_heads
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+ self.window_size = window_size
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+ self.shift_size = shift_size
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+ self.mlp_ratio = mlp_ratio
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+ if min(self.input_resolution) <= self.window_size:
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+ # if window size is larger than input resolution, we don't partition windows
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+ self.shift_size = 0
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+ self.window_size = min(self.input_resolution)
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+ assert 0 <= self.shift_size < self.window_size, "shift_size must in 0-window_size"
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+
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+ self.norm1 = norm_layer(dim)
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+ self.attn = WindowAttention(
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+ dim, window_size=to_2tuple(self.window_size), num_heads=num_heads,
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+ qkv_bias=qkv_bias, qk_scale=qk_scale, attn_drop=attn_drop, proj_drop=drop)
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+
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+ self.drop_path = DropPath(drop_path) if drop_path > 0. else nn.Identity()
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+ self.norm2 = norm_layer(dim)
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+ mlp_hidden_dim = int(dim * mlp_ratio)
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+ self.mlp = Mlp(in_features=dim, hidden_features=mlp_hidden_dim, act_layer=act_layer, drop=drop)
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+
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+ if self.shift_size > 0:
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+ # calculate attention mask for SW-MSA
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+ H, W = self.input_resolution
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+ img_mask = torch.zeros((1, H, W, 1)) # 1 H W 1
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+ h_slices = (slice(0, -self.window_size),
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+ slice(-self.window_size, -self.shift_size),
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+ slice(-self.shift_size, None))
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+ w_slices = (slice(0, -self.window_size),
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+ slice(-self.window_size, -self.shift_size),
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+ slice(-self.shift_size, None))
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+ cnt = 0
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+ for h in h_slices:
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+ for w in w_slices:
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+ img_mask[:, h, w, :] = cnt
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+ cnt += 1
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+
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+ mask_windows = window_partition(img_mask, self.window_size) # nW, window_size, window_size, 1
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+ mask_windows = mask_windows.view(-1, self.window_size * self.window_size)
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+ attn_mask = mask_windows.unsqueeze(1) - mask_windows.unsqueeze(2)
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+ attn_mask = attn_mask.masked_fill(attn_mask != 0, float(-100.0)).masked_fill(attn_mask == 0, float(0.0))
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+ else:
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+ attn_mask = None
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+
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+ self.register_buffer("attn_mask", attn_mask)
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+ self.fused_window_process = fused_window_process
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+
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+ def forward(self, x):
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+ H, W = self.input_resolution
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+ B, L, C = x.shape
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+ assert L == H * W, "input feature has wrong size"
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+
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+ shortcut = x
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+ x = self.norm1(x)
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+ x = x.view(B, H, W, C)
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+
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+ # cyclic shift
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+ if self.shift_size > 0:
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+ if not self.fused_window_process:
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+ shifted_x = torch.roll(x, shifts=(-self.shift_size, -self.shift_size), dims=(1, 2))
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+ # partition windows
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+ x_windows = window_partition(shifted_x, self.window_size) # nW*B, window_size, window_size, C
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+ else:
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+ x_windows = WindowProcess.apply(x, B, H, W, C, -self.shift_size, self.window_size)
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+ else:
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+ shifted_x = x
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+ # partition windows
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+ x_windows = window_partition(shifted_x, self.window_size) # nW*B, window_size, window_size, C
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+
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+ x_windows = x_windows.view(-1, self.window_size * self.window_size, C) # nW*B, window_size*window_size, C
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+
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+ # W-MSA/SW-MSA
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+ attn_windows = self.attn(x_windows, mask=self.attn_mask) # nW*B, window_size*window_size, C
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+
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+ # merge windows
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+ attn_windows = attn_windows.view(-1, self.window_size, self.window_size, C)
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+
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+ # reverse cyclic shift
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+ if self.shift_size > 0:
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+ if not self.fused_window_process:
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+ shifted_x = window_reverse(attn_windows, self.window_size, H, W) # B H' W' C
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+ x = torch.roll(shifted_x, shifts=(self.shift_size, self.shift_size), dims=(1, 2))
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+ else:
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+ x = WindowProcessReverse.apply(attn_windows, B, H, W, C, self.shift_size, self.window_size)
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+ else:
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+ shifted_x = window_reverse(attn_windows, self.window_size, H, W) # B H' W' C
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+ x = shifted_x
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+ x = x.view(B, H * W, C)
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+ x = shortcut + self.drop_path(x)
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+
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+ # FFN
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+ x = x + self.drop_path(self.mlp(self.norm2(x)))
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+
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+ return x
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+
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+ def extra_repr(self) -> str:
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+ return f"dim={self.dim}, input_resolution={self.input_resolution}, num_heads={self.num_heads}, " \
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+ f"window_size={self.window_size}, shift_size={self.shift_size}, mlp_ratio={self.mlp_ratio}"
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+
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+ def flops(self):
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+ flops = 0
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+ H, W = self.input_resolution
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+ # norm1
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+ flops += self.dim * H * W
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+ # W-MSA/SW-MSA
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+ nW = H * W / self.window_size / self.window_size
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+ flops += nW * self.attn.flops(self.window_size * self.window_size)
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+ # mlp
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+ flops += 2 * H * W * self.dim * self.dim * self.mlp_ratio
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+ # norm2
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+ flops += self.dim * H * W
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+ return flops
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+
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+
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+class PatchMerging(nn.Module):
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+ r""" Patch Merging Layer.
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+
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+ Args:
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+ input_resolution (tuple[int]): Resolution of input feature.
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+ dim (int): Number of input channels.
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+ norm_layer (nn.Module, optional): Normalization layer. Default: nn.LayerNorm
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+ """
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+
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+ def __init__(self, input_resolution, dim, norm_layer=nn.LayerNorm):
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+ super().__init__()
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+ self.input_resolution = input_resolution
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+ self.dim = dim
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+ self.reduction = nn.Linear(4 * dim, 2 * dim, bias=False)
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+ self.norm = norm_layer(4 * dim)
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+
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+ def forward(self, x):
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+ """
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+ x: B, H*W, C
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+ """
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+ H, W = self.input_resolution
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+ B, L, C = x.shape
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+ assert L == H * W, "input feature has wrong size"
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+ assert H % 2 == 0 and W % 2 == 0, f"x size ({H}*{W}) are not even."
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+
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+ x = x.view(B, H, W, C)
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+
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+ x0 = x[:, 0::2, 0::2, :] # B H/2 W/2 C
|
|
|
+ x1 = x[:, 1::2, 0::2, :] # B H/2 W/2 C
|
|
|
+ x2 = x[:, 0::2, 1::2, :] # B H/2 W/2 C
|
|
|
+ x3 = x[:, 1::2, 1::2, :] # B H/2 W/2 C
|
|
|
+ x = torch.cat([x0, x1, x2, x3], -1) # B H/2 W/2 4*C
|
|
|
+ x = x.view(B, -1, 4 * C) # B H/2*W/2 4*C
|
|
|
+
|
|
|
+ x = self.norm(x)
|
|
|
+ x = self.reduction(x)
|
|
|
+
|
|
|
+ return x
|
|
|
+
|
|
|
+ def extra_repr(self) -> str:
|
|
|
+ return f"input_resolution={self.input_resolution}, dim={self.dim}"
|
|
|
+
|
|
|
+ def flops(self):
|
|
|
+ H, W = self.input_resolution
|
|
|
+ flops = H * W * self.dim
|
|
|
+ flops += (H // 2) * (W // 2) * 4 * self.dim * 2 * self.dim
|
|
|
+ return flops
|
|
|
+
|
|
|
+
|
|
|
+class BasicLayer(nn.Module):
|
|
|
+ """ A basic Swin Transformer layer for one stage.
|
|
|
+
|
|
|
+ Args:
|
|
|
+ dim (int): Number of input channels.
|
|
|
+ input_resolution (tuple[int]): Input resolution.
|
|
|
+ depth (int): Number of blocks.
|
|
|
+ num_heads (int): Number of attention heads.
|
|
|
+ window_size (int): Local window size.
|
|
|
+ mlp_ratio (float): Ratio of mlp hidden dim to embedding dim.
|
|
|
+ qkv_bias (bool, optional): If True, add a learnable bias to query, key, value. Default: True
|
|
|
+ qk_scale (float | None, optional): Override default qk scale of head_dim ** -0.5 if set.
|
|
|
+ drop (float, optional): Dropout rate. Default: 0.0
|
|
|
+ attn_drop (float, optional): Attention dropout rate. Default: 0.0
|
|
|
+ drop_path (float | tuple[float], optional): Stochastic depth rate. Default: 0.0
|
|
|
+ norm_layer (nn.Module, optional): Normalization layer. Default: nn.LayerNorm
|
|
|
+ downsample (nn.Module | None, optional): Downsample layer at the end of the layer. Default: None
|
|
|
+ use_checkpoint (bool): Whether to use checkpointing to save memory. Default: False.
|
|
|
+ fused_window_process (bool, optional): If True, use one kernel to fused window shift & window partition for acceleration, similar for the reversed part. Default: False
|
|
|
+ """
|
|
|
+
|
|
|
+ def __init__(self, dim, input_resolution, depth, num_heads, window_size,
|
|
|
+ mlp_ratio=4., qkv_bias=True, qk_scale=None, drop=0., attn_drop=0.,
|
|
|
+ drop_path=0., norm_layer=nn.LayerNorm, downsample=None, use_checkpoint=False,
|
|
|
+ fused_window_process=False):
|
|
|
+
|
|
|
+ super().__init__()
|
|
|
+ self.dim = dim
|
|
|
+ self.input_resolution = input_resolution
|
|
|
+ self.depth = depth
|
|
|
+ self.use_checkpoint = use_checkpoint
|
|
|
+
|
|
|
+ # build blocks
|
|
|
+ self.blocks = nn.ModuleList([
|
|
|
+ SwinTransformerBlock(dim=dim, input_resolution=input_resolution,
|
|
|
+ num_heads=num_heads, window_size=window_size,
|
|
|
+ shift_size=0 if (i % 2 == 0) else window_size // 2,
|
|
|
+ mlp_ratio=mlp_ratio,
|
|
|
+ qkv_bias=qkv_bias, qk_scale=qk_scale,
|
|
|
+ drop=drop, attn_drop=attn_drop,
|
|
|
+ drop_path=drop_path[i] if isinstance(drop_path, list) else drop_path,
|
|
|
+ norm_layer=norm_layer,
|
|
|
+ fused_window_process=fused_window_process)
|
|
|
+ for i in range(depth)])
|
|
|
+
|
|
|
+ # patch merging layer
|
|
|
+ if downsample is not None:
|
|
|
+ self.downsample = downsample(input_resolution, dim=dim, norm_layer=norm_layer)
|
|
|
+ else:
|
|
|
+ self.downsample = None
|
|
|
+
|
|
|
+ def forward(self, x):
|
|
|
+ for blk in self.blocks:
|
|
|
+ if self.use_checkpoint:
|
|
|
+ x = checkpoint.checkpoint(blk, x)
|
|
|
+ else:
|
|
|
+ x = blk(x)
|
|
|
+ if self.downsample is not None:
|
|
|
+ x = self.downsample(x)
|
|
|
+ return x
|
|
|
+
|
|
|
+ def extra_repr(self) -> str:
|
|
|
+ return f"dim={self.dim}, input_resolution={self.input_resolution}, depth={self.depth}"
|
|
|
+
|
|
|
+ def flops(self):
|
|
|
+ flops = 0
|
|
|
+ for blk in self.blocks:
|
|
|
+ flops += blk.flops()
|
|
|
+ if self.downsample is not None:
|
|
|
+ flops += self.downsample.flops()
|
|
|
+ return flops
|
|
|
+
|
|
|
+
|
|
|
+class PatchEmbed(nn.Module):
|
|
|
+ r""" Image to Patch Embedding
|
|
|
+
|
|
|
+ Args:
|
|
|
+ img_size (int): Image size. Default: 224.
|
|
|
+ patch_size (int): Patch token size. Default: 4.
|
|
|
+ in_chans (int): Number of input image channels. Default: 3.
|
|
|
+ embed_dim (int): Number of linear projection output channels. Default: 96.
|
|
|
+ norm_layer (nn.Module, optional): Normalization layer. Default: None
|
|
|
+ """
|
|
|
+
|
|
|
+ def __init__(self, img_size=224, patch_size=4, in_chans=3, embed_dim=96, norm_layer=None):
|
|
|
+ super().__init__()
|
|
|
+ img_size = to_2tuple(img_size)
|
|
|
+ patch_size = to_2tuple(patch_size)
|
|
|
+ patches_resolution = [img_size[0] // patch_size[0], img_size[1] // patch_size[1]]
|
|
|
+ self.img_size = img_size
|
|
|
+ self.patch_size = patch_size
|
|
|
+ self.patches_resolution = patches_resolution
|
|
|
+ self.num_patches = patches_resolution[0] * patches_resolution[1]
|
|
|
+
|
|
|
+ self.in_chans = in_chans
|
|
|
+ self.embed_dim = embed_dim
|
|
|
+
|
|
|
+ self.proj = nn.Conv2d(in_chans, embed_dim, kernel_size=patch_size, stride=patch_size)
|
|
|
+ if norm_layer is not None:
|
|
|
+ self.norm = norm_layer(embed_dim)
|
|
|
+ else:
|
|
|
+ self.norm = None
|
|
|
+
|
|
|
+ def forward(self, x):
|
|
|
+ B, C, H, W = x.shape
|
|
|
+ # FIXME look at relaxing size constraints
|
|
|
+ assert H == self.img_size[0] and W == self.img_size[1], \
|
|
|
+ f"Input image size ({H}*{W}) doesn't match model ({self.img_size[0]}*{self.img_size[1]})."
|
|
|
+ x = self.proj(x).flatten(2).transpose(1, 2) # B Ph*Pw C
|
|
|
+ if self.norm is not None:
|
|
|
+ x = self.norm(x)
|
|
|
+ return x
|
|
|
+
|
|
|
+ def flops(self):
|
|
|
+ Ho, Wo = self.patches_resolution
|
|
|
+ flops = Ho * Wo * self.embed_dim * self.in_chans * (self.patch_size[0] * self.patch_size[1])
|
|
|
+ if self.norm is not None:
|
|
|
+ flops += Ho * Wo * self.embed_dim
|
|
|
+ return flops
|
|
|
+
|
|
|
+
|
|
|
+class SwinTransformer(nn.Module):
|
|
|
+ r""" Swin Transformer
|
|
|
+ A PyTorch impl of : `Swin Transformer: Hierarchical Vision Transformer using Shifted Windows` -
|
|
|
+ https://arxiv.org/pdf/2103.14030
|
|
|
+
|
|
|
+ Args:
|
|
|
+ img_size (int | tuple(int)): Input image size. Default 224
|
|
|
+ patch_size (int | tuple(int)): Patch size. Default: 4
|
|
|
+ in_chans (int): Number of input image channels. Default: 3
|
|
|
+ num_classes (int): Number of classes for classification head. Default: 1000
|
|
|
+ embed_dim (int): Patch embedding dimension. Default: 96
|
|
|
+ depths (tuple(int)): Depth of each Swin Transformer layer.
|
|
|
+ num_heads (tuple(int)): Number of attention heads in different layers.
|
|
|
+ window_size (int): Window size. Default: 7
|
|
|
+ mlp_ratio (float): Ratio of mlp hidden dim to embedding dim. Default: 4
|
|
|
+ qkv_bias (bool): If True, add a learnable bias to query, key, value. Default: True
|
|
|
+ qk_scale (float): Override default qk scale of head_dim ** -0.5 if set. Default: None
|
|
|
+ drop_rate (float): Dropout rate. Default: 0
|
|
|
+ attn_drop_rate (float): Attention dropout rate. Default: 0
|
|
|
+ drop_path_rate (float): Stochastic depth rate. Default: 0.1
|
|
|
+ norm_layer (nn.Module): Normalization layer. Default: nn.LayerNorm.
|
|
|
+ ape (bool): If True, add absolute position embedding to the patch embedding. Default: False
|
|
|
+ patch_norm (bool): If True, add normalization after patch embedding. Default: True
|
|
|
+ use_checkpoint (bool): Whether to use checkpointing to save memory. Default: False
|
|
|
+ fused_window_process (bool, optional): If True, use one kernel to fused window shift & window partition for acceleration, similar for the reversed part. Default: False
|
|
|
+ """
|
|
|
+
|
|
|
+ def __init__(self, img_size=224, patch_size=4, in_chans=3, num_classes=1000,
|
|
|
+ embed_dim=96, depths=[2, 2, 6, 2], num_heads=[3, 6, 12, 24],
|
|
|
+ window_size=7, mlp_ratio=4., qkv_bias=True, qk_scale=None,
|
|
|
+ drop_rate=0., attn_drop_rate=0., drop_path_rate=0.1,
|
|
|
+ norm_layer=nn.LayerNorm, ape=False, patch_norm=True,
|
|
|
+ use_checkpoint=False, fused_window_process=False, **kwargs):
|
|
|
+ super().__init__()
|
|
|
+
|
|
|
+ self.num_classes = num_classes
|
|
|
+ self.num_layers = len(depths)
|
|
|
+ self.embed_dim = embed_dim
|
|
|
+ self.ape = ape
|
|
|
+ self.patch_norm = patch_norm
|
|
|
+ self.num_features = int(embed_dim * 2 ** (self.num_layers - 1))
|
|
|
+ self.mlp_ratio = mlp_ratio
|
|
|
+
|
|
|
+ # split image into non-overlapping patches
|
|
|
+ self.patch_embed = PatchEmbed(
|
|
|
+ img_size=img_size, patch_size=patch_size, in_chans=in_chans, embed_dim=embed_dim,
|
|
|
+ norm_layer=norm_layer if self.patch_norm else None)
|
|
|
+ num_patches = self.patch_embed.num_patches
|
|
|
+ patches_resolution = self.patch_embed.patches_resolution
|
|
|
+ self.patches_resolution = patches_resolution
|
|
|
+
|
|
|
+ # absolute position embedding
|
|
|
+ if self.ape:
|
|
|
+ self.absolute_pos_embed = nn.Parameter(torch.zeros(1, num_patches, embed_dim))
|
|
|
+ trunc_normal_(self.absolute_pos_embed, std=.02)
|
|
|
+
|
|
|
+ self.pos_drop = nn.Dropout(p=drop_rate)
|
|
|
+
|
|
|
+ # stochastic depth
|
|
|
+ dpr = [x.item() for x in torch.linspace(0, drop_path_rate, sum(depths))] # stochastic depth decay rule
|
|
|
+
|
|
|
+ # build layers
|
|
|
+ self.layers = nn.ModuleList()
|
|
|
+ for i_layer in range(self.num_layers):
|
|
|
+ layer = BasicLayer(dim=int(embed_dim * 2 ** i_layer),
|
|
|
+ input_resolution=(patches_resolution[0] // (2 ** i_layer),
|
|
|
+ patches_resolution[1] // (2 ** i_layer)),
|
|
|
+ depth=depths[i_layer],
|
|
|
+ num_heads=num_heads[i_layer],
|
|
|
+ window_size=window_size,
|
|
|
+ mlp_ratio=self.mlp_ratio,
|
|
|
+ qkv_bias=qkv_bias, qk_scale=qk_scale,
|
|
|
+ drop=drop_rate, attn_drop=attn_drop_rate,
|
|
|
+ drop_path=dpr[sum(depths[:i_layer]):sum(depths[:i_layer + 1])],
|
|
|
+ norm_layer=norm_layer,
|
|
|
+ downsample=PatchMerging if (i_layer < self.num_layers - 1) else None,
|
|
|
+ use_checkpoint=use_checkpoint,
|
|
|
+ fused_window_process=fused_window_process)
|
|
|
+ self.layers.append(layer)
|
|
|
+
|
|
|
+ self.norm = norm_layer(self.num_features)
|
|
|
+ self.avgpool = nn.AdaptiveAvgPool1d(1)
|
|
|
+ self.head = nn.Linear(self.num_features, num_classes) if num_classes > 0 else nn.Identity()
|
|
|
+
|
|
|
+ self.apply(self._init_weights)
|
|
|
+
|
|
|
+ def _init_weights(self, m):
|
|
|
+ if isinstance(m, nn.Linear):
|
|
|
+ trunc_normal_(m.weight, std=.02)
|
|
|
+ if isinstance(m, nn.Linear) and m.bias is not None:
|
|
|
+ nn.init.constant_(m.bias, 0)
|
|
|
+ elif isinstance(m, nn.LayerNorm):
|
|
|
+ nn.init.constant_(m.bias, 0)
|
|
|
+ nn.init.constant_(m.weight, 1.0)
|
|
|
+
|
|
|
+ @torch.jit.ignore
|
|
|
+ def no_weight_decay(self):
|
|
|
+ return {'absolute_pos_embed'}
|
|
|
+
|
|
|
+ @torch.jit.ignore
|
|
|
+ def no_weight_decay_keywords(self):
|
|
|
+ return {'relative_position_bias_table'}
|
|
|
+
|
|
|
+ def forward_features(self, x):
|
|
|
+ x = self.patch_embed(x)
|
|
|
+ if self.ape:
|
|
|
+ x = x + self.absolute_pos_embed
|
|
|
+ x = self.pos_drop(x)
|
|
|
+
|
|
|
+ for layer in self.layers:
|
|
|
+ x = layer(x)
|
|
|
+
|
|
|
+ x = self.norm(x) # B L C
|
|
|
+ x = self.avgpool(x.transpose(1, 2)) # B C 1
|
|
|
+ x = torch.flatten(x, 1)
|
|
|
+ return x
|
|
|
+
|
|
|
+ def forward(self, x):
|
|
|
+ x = self.forward_features(x)
|
|
|
+ x = self.head(x)
|
|
|
+ return x
|
|
|
+
|
|
|
+ def flops(self):
|
|
|
+ flops = 0
|
|
|
+ flops += self.patch_embed.flops()
|
|
|
+ for i, layer in enumerate(self.layers):
|
|
|
+ flops += layer.flops()
|
|
|
+ flops += self.num_features * self.patches_resolution[0] * self.patches_resolution[1] // (2 ** self.num_layers)
|
|
|
+ flops += self.num_features * self.num_classes
|
|
|
+ return flops
|