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| # ------------------------------------------------------------------------------------------------ | |
| # Deformable DETR | |
| # Copyright (c) 2020 SenseTime. All Rights Reserved. | |
| # Licensed under the Apache License, Version 2.0 [see LICENSE for details] | |
| # ------------------------------------------------------------------------------------------------ | |
| # Modified from https://github.com/chengdazhi/Deformable-Convolution-V2-PyTorch/tree/pytorch_1.0.0 | |
| # ------------------------------------------------------------------------------------------------ | |
| from __future__ import absolute_import | |
| from __future__ import print_function | |
| from __future__ import division | |
| import warnings | |
| import math | |
| import torch | |
| from torch import nn | |
| import torch.nn.functional as F | |
| from torch.nn.init import xavier_uniform_, constant_ | |
| from ..functions import MSDeformAttnFunction | |
| def _is_power_of_2(n): | |
| if (not isinstance(n, int)) or (n < 0): | |
| raise ValueError("invalid input for _is_power_of_2: {} (type: {})".format(n, type(n))) | |
| return (n & (n-1) == 0) and n != 0 | |
| class MSDeformAttn(nn.Module): | |
| def __init__(self, d_model=256, n_levels=4, n_heads=8, n_points=4): | |
| """ | |
| Multi-Scale Deformable Attention Module | |
| :param d_model hidden dimension | |
| :param n_levels number of feature levels | |
| :param n_heads number of attention heads | |
| :param n_points number of sampling points per attention head per feature level | |
| """ | |
| super().__init__() | |
| if d_model % n_heads != 0: | |
| raise ValueError('d_model must be divisible by n_heads, but got {} and {}'.format(d_model, n_heads)) | |
| _d_per_head = d_model // n_heads | |
| # you'd better set _d_per_head to a power of 2 which is more efficient in our CUDA implementation | |
| if not _is_power_of_2(_d_per_head): | |
| warnings.warn("You'd better set d_model in MSDeformAttn to make the dimension of each attention head a power of 2 " | |
| "which is more efficient in our CUDA implementation.") | |
| self.im2col_step = 64 | |
| self.d_model = d_model | |
| self.n_levels = n_levels | |
| self.n_heads = n_heads | |
| self.n_points = n_points | |
| self.sampling_offsets = nn.Linear(d_model, n_heads * n_levels * n_points * 2) | |
| self.attention_weights = nn.Linear(d_model, n_heads * n_levels * n_points) | |
| self.value_proj = nn.Linear(d_model, d_model) | |
| self.output_proj = nn.Linear(d_model, d_model) | |
| self._reset_parameters() | |
| def _reset_parameters(self): | |
| constant_(self.sampling_offsets.weight.data, 0.) | |
| thetas = torch.arange(self.n_heads, dtype=torch.float32) * (2.0 * math.pi / self.n_heads) | |
| grid_init = torch.stack([thetas.cos(), thetas.sin()], -1) | |
| grid_init = (grid_init / grid_init.abs().max(-1, keepdim=True)[0]).view(self.n_heads, 1, 1, 2).repeat(1, self.n_levels, self.n_points, 1) | |
| for i in range(self.n_points): | |
| grid_init[:, :, i, :] *= i + 1 | |
| with torch.no_grad(): | |
| self.sampling_offsets.bias = nn.Parameter(grid_init.view(-1)) | |
| constant_(self.attention_weights.weight.data, 0.) | |
| constant_(self.attention_weights.bias.data, 0.) | |
| xavier_uniform_(self.value_proj.weight.data) | |
| constant_(self.value_proj.bias.data, 0.) | |
| xavier_uniform_(self.output_proj.weight.data) | |
| constant_(self.output_proj.bias.data, 0.) | |
| def forward(self, query, reference_points, input_flatten, input_spatial_shapes, input_level_start_index, input_padding_mask=None): | |
| """ | |
| :param query (N, Length_{query}, C) | |
| :param reference_points (N, Length_{query}, n_levels, 2), range in [0, 1], top-left (0,0), bottom-right (1, 1), including padding area | |
| or (N, Length_{query}, n_levels, 4), add additional (w, h) to form reference boxes | |
| :param input_flatten (N, \sum_{l=0}^{L-1} H_l \cdot W_l, C) | |
| :param input_spatial_shapes (n_levels, 2), [(H_0, W_0), (H_1, W_1), ..., (H_{L-1}, W_{L-1})] | |
| :param input_level_start_index (n_levels, ), [0, H_0*W_0, H_0*W_0+H_1*W_1, H_0*W_0+H_1*W_1+H_2*W_2, ..., H_0*W_0+H_1*W_1+...+H_{L-1}*W_{L-1}] | |
| :param input_padding_mask (N, \sum_{l=0}^{L-1} H_l \cdot W_l), True for padding elements, False for non-padding elements | |
| :return output (N, Length_{query}, C) | |
| """ | |
| N, Len_q, _ = query.shape | |
| N, Len_in, _ = input_flatten.shape | |
| assert (input_spatial_shapes[:, 0] * input_spatial_shapes[:, 1]).sum() == Len_in | |
| value = self.value_proj(input_flatten) | |
| if input_padding_mask is not None: | |
| value = value.masked_fill(input_padding_mask[..., None], float(0)) | |
| value = value.view(N, Len_in, self.n_heads, self.d_model // self.n_heads) | |
| sampling_offsets = self.sampling_offsets(query).view(N, Len_q, self.n_heads, self.n_levels, self.n_points, 2) | |
| attention_weights = self.attention_weights(query).view(N, Len_q, self.n_heads, self.n_levels * self.n_points) | |
| attention_weights = F.softmax(attention_weights, -1).view(N, Len_q, self.n_heads, self.n_levels, self.n_points) | |
| # N, Len_q, n_heads, n_levels, n_points, 2 | |
| if reference_points.shape[-1] == 2: | |
| offset_normalizer = torch.stack([input_spatial_shapes[..., 1], input_spatial_shapes[..., 0]], -1) | |
| sampling_locations = reference_points[:, :, None, :, None, :] \ | |
| + sampling_offsets / offset_normalizer[None, None, None, :, None, :] | |
| elif reference_points.shape[-1] == 4: | |
| sampling_locations = reference_points[:, :, None, :, None, :2] \ | |
| + sampling_offsets / self.n_points * reference_points[:, :, None, :, None, 2:] * 0.5 | |
| else: | |
| raise ValueError( | |
| 'Last dim of reference_points must be 2 or 4, but get {} instead.'.format(reference_points.shape[-1])) | |
| # for amp | |
| if value.dtype == torch.float16: | |
| # for mixed precision | |
| output = MSDeformAttnFunction.apply( | |
| value.to(torch.float32), input_spatial_shapes, input_level_start_index, sampling_locations.to(torch.float32), attention_weights, self.im2col_step) | |
| output = output.to(torch.float16) | |
| output = self.output_proj(output) | |
| return output | |
| output = MSDeformAttnFunction.apply( | |
| value, input_spatial_shapes, input_level_start_index, sampling_locations, attention_weights, self.im2col_step) | |
| output = self.output_proj(output) | |
| return output | |