mmdet/models/layers/transformer/utils.py

# Copyright (c) OpenMMLab. All rights reserved.
import math
import warnings
from typing import Optional, Sequence, Tuple, Union

import torch
import torch.nn.functional as F
from mmcv.cnn import (Linear, build_activation_layer, build_conv_layer,
                      build_norm_layer)
from mmcv.cnn.bricks.drop import Dropout
from mmengine.model import BaseModule, ModuleList
from mmengine.utils import to_2tuple
from torch import Tensor, nn

from mmdet.registry import MODELS
from mmdet.utils import OptConfigType, OptMultiConfig


def nlc_to_nchw(x: Tensor, hw_shape: Sequence[int]) -> Tensor:
    """Convert [N, L, C] shape tensor to [N, C, H, W] shape tensor.

    Args:
        x (Tensor): The input tensor of shape [N, L, C] before conversion.
        hw_shape (Sequence[int]): The height and width of output feature map.

    Returns:
        Tensor: The output tensor of shape [N, C, H, W] after conversion.
    """
    H, W = hw_shape
    assert len(x.shape) == 3
    B, L, C = x.shape
    assert L == H * W, 'The seq_len does not match H, W'
    return x.transpose(1, 2).reshape(B, C, H, W).contiguous()


def nchw_to_nlc(x):
    """Flatten [N, C, H, W] shape tensor to [N, L, C] shape tensor.

    Args:
        x (Tensor): The input tensor of shape [N, C, H, W] before conversion.

    Returns:
        Tensor: The output tensor of shape [N, L, C] after conversion.
    """
    assert len(x.shape) == 4
    return x.flatten(2).transpose(1, 2).contiguous()


def coordinate_to_encoding(coord_tensor: Tensor,
                           num_feats: int = 128,
                           temperature: int = 10000,
                           scale: float = 2 * math.pi):
    """Convert coordinate tensor to positional encoding.

    Args:
        coord_tensor (Tensor): Coordinate tensor to be converted to
            positional encoding. With the last dimension as 2 or 4.
        num_feats (int, optional): The feature dimension for each position
            along x-axis or y-axis. Note the final returned dimension
            for each position is 2 times of this value. Defaults to 128.
        temperature (int, optional): The temperature used for scaling
            the position embedding. Defaults to 10000.
        scale (float, optional): A scale factor that scales the position
            embedding. The scale will be used only when `normalize` is True.
            Defaults to 2*pi.
    Returns:
        Tensor: Returned encoded positional tensor.
    """
    dim_t = torch.arange(
        num_feats, dtype=torch.float32, device=coord_tensor.device)
    dim_t = temperature**(2 * (dim_t // 2) / num_feats)
    x_embed = coord_tensor[..., 0] * scale
    y_embed = coord_tensor[..., 1] * scale
    pos_x = x_embed[..., None] / dim_t
    pos_y = y_embed[..., None] / dim_t
    pos_x = torch.stack((pos_x[..., 0::2].sin(), pos_x[..., 1::2].cos()),
                        dim=-1).flatten(2)
    pos_y = torch.stack((pos_y[..., 0::2].sin(), pos_y[..., 1::2].cos()),
                        dim=-1).flatten(2)
    if coord_tensor.size(-1) == 2:
        pos = torch.cat((pos_y, pos_x), dim=-1)
    elif coord_tensor.size(-1) == 4:
        w_embed = coord_tensor[..., 2] * scale
        pos_w = w_embed[..., None] / dim_t
        pos_w = torch.stack((pos_w[..., 0::2].sin(), pos_w[..., 1::2].cos()),
                            dim=-1).flatten(2)

        h_embed = coord_tensor[..., 3] * scale
        pos_h = h_embed[..., None] / dim_t
        pos_h = torch.stack((pos_h[..., 0::2].sin(), pos_h[..., 1::2].cos()),
                            dim=-1).flatten(2)

        pos = torch.cat((pos_y, pos_x, pos_w, pos_h), dim=-1)
    else:
        raise ValueError('Unknown pos_tensor shape(-1):{}'.format(
            coord_tensor.size(-1)))
    return pos


def inverse_sigmoid(x: Tensor, eps: float = 1e-5) -> Tensor:
    """Inverse function of sigmoid.

    Args:
        x (Tensor): The tensor to do the inverse.
        eps (float): EPS avoid numerical overflow. Defaults 1e-5.
    Returns:
        Tensor: The x has passed the inverse function of sigmoid, has the same
        shape with input.
    """
    x = x.clamp(min=0, max=1)
    x1 = x.clamp(min=eps)
    x2 = (1 - x).clamp(min=eps)
    return torch.log(x1 / x2)


class AdaptivePadding(nn.Module):
    """Applies padding to input (if needed) so that input can get fully covered
    by filter you specified. It support two modes "same" and "corner". The
    "same" mode is same with "SAME" padding mode in TensorFlow, pad zero around
    input. The "corner"  mode would pad zero to bottom right.

    Args:
        kernel_size (int | tuple): Size of the kernel:
        stride (int | tuple): Stride of the filter. Default: 1:
        dilation (int | tuple): Spacing between kernel elements.
            Default: 1
        padding (str): Support "same" and "corner", "corner" mode
            would pad zero to bottom right, and "same" mode would
            pad zero around input. Default: "corner".
    Example:
        >>> kernel_size = 16
        >>> stride = 16
        >>> dilation = 1
        >>> input = torch.rand(1, 1, 15, 17)
        >>> adap_pad = AdaptivePadding(
        >>>     kernel_size=kernel_size,
        >>>     stride=stride,
        >>>     dilation=dilation,
        >>>     padding="corner")
        >>> out = adap_pad(input)
        >>> assert (out.shape[2], out.shape[3]) == (16, 32)
        >>> input = torch.rand(1, 1, 16, 17)
        >>> out = adap_pad(input)
        >>> assert (out.shape[2], out.shape[3]) == (16, 32)
    """

    def __init__(self, kernel_size=1, stride=1, dilation=1, padding='corner'):

        super(AdaptivePadding, self).__init__()

        assert padding in ('same', 'corner')

        kernel_size = to_2tuple(kernel_size)
        stride = to_2tuple(stride)
        padding = to_2tuple(padding)
        dilation = to_2tuple(dilation)

        self.padding = padding
        self.kernel_size = kernel_size
        self.stride = stride
        self.dilation = dilation

    def get_pad_shape(self, input_shape):
        input_h, input_w = input_shape
        kernel_h, kernel_w = self.kernel_size
        stride_h, stride_w = self.stride
        output_h = math.ceil(input_h / stride_h)
        output_w = math.ceil(input_w / stride_w)
        pad_h = max((output_h - 1) * stride_h +
                    (kernel_h - 1) * self.dilation[0] + 1 - input_h, 0)
        pad_w = max((output_w - 1) * stride_w +
                    (kernel_w - 1) * self.dilation[1] + 1 - input_w, 0)
        return pad_h, pad_w

    def forward(self, x):
        pad_h, pad_w = self.get_pad_shape(x.size()[-2:])
        if pad_h > 0 or pad_w > 0:
            if self.padding == 'corner':
                x = F.pad(x, [0, pad_w, 0, pad_h])
            elif self.padding == 'same':
                x = F.pad(x, [
                    pad_w // 2, pad_w - pad_w // 2, pad_h // 2,
                    pad_h - pad_h // 2
                ])
        return x


class PatchEmbed(BaseModule):
    """Image to Patch Embedding.

    We use a conv layer to implement PatchEmbed.

    Args:
        in_channels (int): The num of input channels. Default: 3
        embed_dims (int): The dimensions of embedding. Default: 768
        conv_type (str): The config dict for embedding
            conv layer type selection. Default: "Conv2d.
        kernel_size (int): The kernel_size of embedding conv. Default: 16.
        stride (int): The slide stride of embedding conv.
            Default: None (Would be set as `kernel_size`).
        padding (int | tuple | string ): The padding length of
            embedding conv. When it is a string, it means the mode
            of adaptive padding, support "same" and "corner" now.
            Default: "corner".
        dilation (int): The dilation rate of embedding conv. Default: 1.
        bias (bool): Bias of embed conv. Default: True.
        norm_cfg (dict, optional): Config dict for normalization layer.
            Default: None.
        input_size (int | tuple | None): The size of input, which will be
            used to calculate the out size. Only work when `dynamic_size`
            is False. Default: None.
        init_cfg (`mmengine.ConfigDict`, optional): The Config for
            initialization. Default: None.
    """

    def __init__(self,
                 in_channels: int = 3,
                 embed_dims: int = 768,
                 conv_type: str = 'Conv2d',
                 kernel_size: int = 16,
                 stride: int = 16,
                 padding: Union[int, tuple, str] = 'corner',
                 dilation: int = 1,
                 bias: bool = True,
                 norm_cfg: OptConfigType = None,
                 input_size: Union[int, tuple] = None,
                 init_cfg: OptConfigType = None) -> None:
        super(PatchEmbed, self).__init__(init_cfg=init_cfg)

        self.embed_dims = embed_dims
        if stride is None:
            stride = kernel_size

        kernel_size = to_2tuple(kernel_size)
        stride = to_2tuple(stride)
        dilation = to_2tuple(dilation)

        if isinstance(padding, str):
            self.adap_padding = AdaptivePadding(
                kernel_size=kernel_size,
                stride=stride,
                dilation=dilation,
                padding=padding)
            # disable the padding of conv
            padding = 0
        else:
            self.adap_padding = None
        padding = to_2tuple(padding)

        self.projection = build_conv_layer(
            dict(type=conv_type),
            in_channels=in_channels,
            out_channels=embed_dims,
            kernel_size=kernel_size,
            stride=stride,
            padding=padding,
            dilation=dilation,
            bias=bias)

        if norm_cfg is not None:
            self.norm = build_norm_layer(norm_cfg, embed_dims)[1]
        else:
            self.norm = None

        if input_size:
            input_size = to_2tuple(input_size)
            # `init_out_size` would be used outside to
            # calculate the num_patches
            # when `use_abs_pos_embed` outside
            self.init_input_size = input_size
            if self.adap_padding:
                pad_h, pad_w = self.adap_padding.get_pad_shape(input_size)
                input_h, input_w = input_size
                input_h = input_h + pad_h
                input_w = input_w + pad_w
                input_size = (input_h, input_w)

            # https://pytorch.org/docs/stable/generated/torch.nn.Conv2d.html
            h_out = (input_size[0] + 2 * padding[0] - dilation[0] *
                     (kernel_size[0] - 1) - 1) // stride[0] + 1
            w_out = (input_size[1] + 2 * padding[1] - dilation[1] *
                     (kernel_size[1] - 1) - 1) // stride[1] + 1
            self.init_out_size = (h_out, w_out)
        else:
            self.init_input_size = None
            self.init_out_size = None

    def forward(self, x: Tensor) -> Tuple[Tensor, Tuple[int]]:
        """
        Args:
            x (Tensor): Has shape (B, C, H, W). In most case, C is 3.

        Returns:
            tuple: Contains merged results and its spatial shape.

                - x (Tensor): Has shape (B, out_h * out_w, embed_dims)
                - out_size (tuple[int]): Spatial shape of x, arrange as
                    (out_h, out_w).
        """

        if self.adap_padding:
            x = self.adap_padding(x)

        x = self.projection(x)
        out_size = (x.shape[2], x.shape[3])
        x = x.flatten(2).transpose(1, 2)
        if self.norm is not None:
            x = self.norm(x)
        return x, out_size


class PatchMerging(BaseModule):
    """Merge patch feature map.

    This layer groups feature map by kernel_size, and applies norm and linear
    layers to the grouped feature map. Our implementation uses `nn.Unfold` to
    merge patch, which is about 25% faster than original implementation.
    Instead, we need to modify pretrained models for compatibility.

    Args:
        in_channels (int): The num of input channels.
            to gets fully covered by filter and stride you specified..
            Default: True.
        out_channels (int): The num of output channels.
        kernel_size (int | tuple, optional): the kernel size in the unfold
            layer. Defaults to 2.
        stride (int | tuple, optional): the stride of the sliding blocks in the
            unfold layer. Default: None. (Would be set as `kernel_size`)
        padding (int | tuple | string ): The padding length of
            embedding conv. When it is a string, it means the mode
            of adaptive padding, support "same" and "corner" now.
            Default: "corner".
        dilation (int | tuple, optional): dilation parameter in the unfold
            layer. Default: 1.
        bias (bool, optional): Whether to add bias in linear layer or not.
            Defaults: False.
        norm_cfg (dict, optional): Config dict for normalization layer.
            Default: dict(type='LN').
        init_cfg (dict, optional): The extra config for initialization.
            Default: None.
    """

    def __init__(self,
                 in_channels: int,
                 out_channels: int,
                 kernel_size: Optional[Union[int, tuple]] = 2,
                 stride: Optional[Union[int, tuple]] = None,
                 padding: Union[int, tuple, str] = 'corner',
                 dilation: Optional[Union[int, tuple]] = 1,
                 bias: Optional[bool] = False,
                 norm_cfg: OptConfigType = dict(type='LN'),
                 init_cfg: OptConfigType = None) -> None:
        super().__init__(init_cfg=init_cfg)
        self.in_channels = in_channels
        self.out_channels = out_channels
        if stride:
            stride = stride
        else:
            stride = kernel_size

        kernel_size = to_2tuple(kernel_size)
        stride = to_2tuple(stride)
        dilation = to_2tuple(dilation)

        if isinstance(padding, str):
            self.adap_padding = AdaptivePadding(
                kernel_size=kernel_size,
                stride=stride,
                dilation=dilation,
                padding=padding)
            # disable the padding of unfold
            padding = 0
        else:
            self.adap_padding = None

        padding = to_2tuple(padding)
        self.sampler = nn.Unfold(
            kernel_size=kernel_size,
            dilation=dilation,
            padding=padding,
            stride=stride)

        sample_dim = kernel_size[0] * kernel_size[1] * in_channels

        if norm_cfg is not None:
            self.norm = build_norm_layer(norm_cfg, sample_dim)[1]
        else:
            self.norm = None

        self.reduction = nn.Linear(sample_dim, out_channels, bias=bias)

    def forward(self, x: Tensor,
                input_size: Tuple[int]) -> Tuple[Tensor, Tuple[int]]:
        """
        Args:
            x (Tensor): Has shape (B, H*W, C_in).
            input_size (tuple[int]): The spatial shape of x, arrange as (H, W).
                Default: None.

        Returns:
            tuple: Contains merged results and its spatial shape.

                - x (Tensor): Has shape (B, Merged_H * Merged_W, C_out)
                - out_size (tuple[int]): Spatial shape of x, arrange as
                    (Merged_H, Merged_W).
        """
        B, L, C = x.shape
        assert isinstance(input_size, Sequence), f'Expect ' \
                                                 f'input_size is ' \
                                                 f'`Sequence` ' \
                                                 f'but get {input_size}'

        H, W = input_size
        assert L == H * W, 'input feature has wrong size'

        x = x.view(B, H, W, C).permute([0, 3, 1, 2])  # B, C, H, W
        # Use nn.Unfold to merge patch. About 25% faster than original method,
        # but need to modify pretrained model for compatibility

        if self.adap_padding:
            x = self.adap_padding(x)
            H, W = x.shape[-2:]

        x = self.sampler(x)
        # if kernel_size=2 and stride=2, x should has shape (B, 4*C, H/2*W/2)

        out_h = (H + 2 * self.sampler.padding[0] - self.sampler.dilation[0] *
                 (self.sampler.kernel_size[0] - 1) -
                 1) // self.sampler.stride[0] + 1
        out_w = (W + 2 * self.sampler.padding[1] - self.sampler.dilation[1] *
                 (self.sampler.kernel_size[1] - 1) -
                 1) // self.sampler.stride[1] + 1

        output_size = (out_h, out_w)
        x = x.transpose(1, 2)  # B, H/2*W/2, 4*C
        x = self.norm(x) if self.norm else x
        x = self.reduction(x)
        return x, output_size


class ConditionalAttention(BaseModule):
    """A wrapper of conditional attention, dropout and residual connection.

    Args:
        embed_dims (int): The embedding dimension.
        num_heads (int): Parallel attention heads.
        attn_drop (float): A Dropout layer on attn_output_weights.
            Default: 0.0.
        proj_drop: A Dropout layer after `nn.MultiheadAttention`.
            Default: 0.0.
        cross_attn (bool): Whether the attention module is for cross attention.
            Default: False
        keep_query_pos (bool): Whether to transform query_pos before cross
            attention.
            Default: False.
        batch_first (bool): When it is True, Key, Query and Value are shape of
            (batch, n, embed_dim), otherwise (n, batch, embed_dim).
             Default: True.
        init_cfg (obj:`mmcv.ConfigDict`): The Config for initialization.
            Default: None.
    """

    def __init__(self,
                 embed_dims: int,
                 num_heads: int,
                 attn_drop: float = 0.,
                 proj_drop: float = 0.,
                 cross_attn: bool = False,
                 keep_query_pos: bool = False,
                 batch_first: bool = True,
                 init_cfg: OptMultiConfig = None):
        super().__init__(init_cfg=init_cfg)

        assert batch_first is True, 'Set `batch_first`\
        to False is NOT supported in ConditionalAttention. \
        First dimension of all DETRs in mmdet is `batch`, \
        please set `batch_first` to True.'

        self.cross_attn = cross_attn
        self.keep_query_pos = keep_query_pos
        self.embed_dims = embed_dims
        self.num_heads = num_heads
        self.attn_drop = Dropout(attn_drop)
        self.proj_drop = Dropout(proj_drop)

        self._init_layers()

    def _init_layers(self):
        """Initialize layers for qkv projection."""
        embed_dims = self.embed_dims
        self.qcontent_proj = Linear(embed_dims, embed_dims)
        self.qpos_proj = Linear(embed_dims, embed_dims)
        self.kcontent_proj = Linear(embed_dims, embed_dims)
        self.kpos_proj = Linear(embed_dims, embed_dims)
        self.v_proj = Linear(embed_dims, embed_dims)
        if self.cross_attn:
            self.qpos_sine_proj = Linear(embed_dims, embed_dims)
        self.out_proj = Linear(embed_dims, embed_dims)

        nn.init.constant_(self.out_proj.bias, 0.)

    def forward_attn(self,
                     query: Tensor,
                     key: Tensor,
                     value: Tensor,
                     attn_mask: Tensor = None,
                     key_padding_mask: Tensor = None) -> Tuple[Tensor]:
        """Forward process for `ConditionalAttention`.

        Args:
            query (Tensor): The input query with shape [bs, num_queries,
                embed_dims].
            key (Tensor): The key tensor with shape [bs, num_keys,
                embed_dims].
                If None, the `query` will be used. Defaults to None.
            value (Tensor): The value tensor with same shape as `key`.
                Same in `nn.MultiheadAttention.forward`. Defaults to None.
                If None, the `key` will be used.
            attn_mask (Tensor): ByteTensor mask with shape [num_queries,
                num_keys]. Same in `nn.MultiheadAttention.forward`.
                Defaults to None.
            key_padding_mask (Tensor): ByteTensor with shape [bs, num_keys].
                Defaults to None.
        Returns:
            Tuple[Tensor]: Attention outputs of shape :math:`(N, L, E)`,
            where :math:`N` is the batch size, :math:`L` is the target
            sequence length , and :math:`E` is the embedding dimension
            `embed_dim`. Attention weights per head of shape :math:`
            (num_heads, L, S)`. where :math:`N` is batch size, :math:`L`
            is target sequence length, and :math:`S` is the source sequence
            length.
        """
        assert key.size(1) == value.size(1), \
            f'{"key, value must have the same sequence length"}'
        assert query.size(0) == key.size(0) == value.size(0), \
            f'{"batch size must be equal for query, key, value"}'
        assert query.size(2) == key.size(2), \
            f'{"q_dims, k_dims must be equal"}'
        assert value.size(2) == self.embed_dims, \
            f'{"v_dims must be equal to embed_dims"}'

        bs, tgt_len, hidden_dims = query.size()
        _, src_len, _ = key.size()
        head_dims = hidden_dims // self.num_heads
        v_head_dims = self.embed_dims // self.num_heads
        assert head_dims * self.num_heads == hidden_dims, \
            f'{"hidden_dims must be divisible by num_heads"}'
        scaling = float(head_dims)**-0.5

        q = query * scaling
        k = key
        v = value

        if attn_mask is not None:
            assert attn_mask.dtype == torch.float32 or \
                   attn_mask.dtype == torch.float64 or \
                   attn_mask.dtype == torch.float16 or \
                   attn_mask.dtype == torch.uint8 or \
                   attn_mask.dtype == torch.bool, \
                   'Only float, byte, and bool types are supported for \
                    attn_mask'

            if attn_mask.dtype == torch.uint8:
                warnings.warn('Byte tensor for attn_mask is deprecated.\
                     Use bool tensor instead.')
                attn_mask = attn_mask.to(torch.bool)
            if attn_mask.dim() == 2:
                attn_mask = attn_mask.unsqueeze(0)
                if list(attn_mask.size()) != [1, query.size(1), key.size(1)]:
                    raise RuntimeError(
                        'The size of the 2D attn_mask is not correct.')
            elif attn_mask.dim() == 3:
                if list(attn_mask.size()) != [
                        bs * self.num_heads,
                        query.size(1),
                        key.size(1)
                ]:
                    raise RuntimeError(
                        'The size of the 3D attn_mask is not correct.')
            else:
                raise RuntimeError(
                    "attn_mask's dimension {} is not supported".format(
                        attn_mask.dim()))
        # attn_mask's dim is 3 now.

        if key_padding_mask is not None and key_padding_mask.dtype == int:
            key_padding_mask = key_padding_mask.to(torch.bool)

        q = q.contiguous().view(bs, tgt_len, self.num_heads,
                                head_dims).permute(0, 2, 1, 3).flatten(0, 1)
        if k is not None:
            k = k.contiguous().view(bs, src_len, self.num_heads,
                                    head_dims).permute(0, 2, 1,
                                                       3).flatten(0, 1)
        if v is not None:
            v = v.contiguous().view(bs, src_len, self.num_heads,
                                    v_head_dims).permute(0, 2, 1,
                                                         3).flatten(0, 1)

        if key_padding_mask is not None:
            assert key_padding_mask.size(0) == bs
            assert key_padding_mask.size(1) == src_len

        attn_output_weights = torch.bmm(q, k.transpose(1, 2))
        assert list(attn_output_weights.size()) == [
            bs * self.num_heads, tgt_len, src_len
        ]

        if attn_mask is not None:
            if attn_mask.dtype == torch.bool:
                attn_output_weights.masked_fill_(attn_mask, float('-inf'))
            else:
                attn_output_weights += attn_mask

        if key_padding_mask is not None:
            attn_output_weights = attn_output_weights.view(
                bs, self.num_heads, tgt_len, src_len)
            attn_output_weights = attn_output_weights.masked_fill(
                key_padding_mask.unsqueeze(1).unsqueeze(2),
                float('-inf'),
            )
            attn_output_weights = attn_output_weights.view(
                bs * self.num_heads, tgt_len, src_len)

        attn_output_weights = F.softmax(
            attn_output_weights -
            attn_output_weights.max(dim=-1, keepdim=True)[0],
            dim=-1)
        attn_output_weights = self.attn_drop(attn_output_weights)

        attn_output = torch.bmm(attn_output_weights, v)
        assert list(
            attn_output.size()) == [bs * self.num_heads, tgt_len, v_head_dims]
        attn_output = attn_output.view(bs, self.num_heads, tgt_len,
                                       v_head_dims).permute(0, 2, 1,
                                                            3).flatten(2)
        attn_output = self.out_proj(attn_output)

        # average attention weights over heads
        attn_output_weights = attn_output_weights.view(bs, self.num_heads,
                                                       tgt_len, src_len)
        return attn_output, attn_output_weights.sum(dim=1) / self.num_heads

    def forward(self,
                query: Tensor,
                key: Tensor,
                query_pos: Tensor = None,
                ref_sine_embed: Tensor = None,
                key_pos: Tensor = None,
                attn_mask: Tensor = None,
                key_padding_mask: Tensor = None,
                is_first: bool = False) -> Tensor:
        """Forward function for `ConditionalAttention`.
        Args:
            query (Tensor): The input query with shape [bs, num_queries,
                embed_dims].
            key (Tensor): The key tensor with shape [bs, num_keys,
                embed_dims].
                If None, the `query` will be used. Defaults to None.
            query_pos (Tensor): The positional encoding for query in self
                attention, with the same shape as `x`. If not None, it will
                be added to `x` before forward function.
                Defaults to None.
            query_sine_embed (Tensor): The positional encoding for query in
                cross attention, with the same shape as `x`. If not None, it
                will be added to `x` before forward function.
                Defaults to None.
            key_pos (Tensor): The positional encoding for `key`, with the
                same shape as `key`. Defaults to None. If not None, it will
                be added to `key` before forward function. If None, and
                `query_pos` has the same shape as `key`, then `query_pos`
                will be used for `key_pos`. Defaults to None.
            attn_mask (Tensor): ByteTensor mask with shape [num_queries,
                num_keys]. Same in `nn.MultiheadAttention.forward`.
                Defaults to None.
            key_padding_mask (Tensor): ByteTensor with shape [bs, num_keys].
                Defaults to None.
            is_first (bool): A indicator to tell whether the current layer
                is the first layer of the decoder.
                Defaults to False.
        Returns:
            Tensor: forwarded results with shape
            [bs, num_queries, embed_dims].
        """

        if self.cross_attn:
            q_content = self.qcontent_proj(query)
            k_content = self.kcontent_proj(key)
            v = self.v_proj(key)

            bs, nq, c = q_content.size()
            _, hw, _ = k_content.size()

            k_pos = self.kpos_proj(key_pos)
            if is_first or self.keep_query_pos:
                q_pos = self.qpos_proj(query_pos)
                q = q_content + q_pos
                k = k_content + k_pos
            else:
                q = q_content
                k = k_content
            q = q.view(bs, nq, self.num_heads, c // self.num_heads)
            query_sine_embed = self.qpos_sine_proj(ref_sine_embed)
            query_sine_embed = query_sine_embed.view(bs, nq, self.num_heads,
                                                     c // self.num_heads)
            q = torch.cat([q, query_sine_embed], dim=3).view(bs, nq, 2 * c)
            k = k.view(bs, hw, self.num_heads, c // self.num_heads)
            k_pos = k_pos.view(bs, hw, self.num_heads, c // self.num_heads)
            k = torch.cat([k, k_pos], dim=3).view(bs, hw, 2 * c)
            ca_output = self.forward_attn(
                query=q,
                key=k,
                value=v,
                attn_mask=attn_mask,
                key_padding_mask=key_padding_mask)[0]
            query = query + self.proj_drop(ca_output)
        else:
            q_content = self.qcontent_proj(query)
            q_pos = self.qpos_proj(query_pos)
            k_content = self.kcontent_proj(query)
            k_pos = self.kpos_proj(query_pos)
            v = self.v_proj(query)
            q = q_content if q_pos is None else q_content + q_pos
            k = k_content if k_pos is None else k_content + k_pos
            sa_output = self.forward_attn(
                query=q,
                key=k,
                value=v,
                attn_mask=attn_mask,
                key_padding_mask=key_padding_mask)[0]
            query = query + self.proj_drop(sa_output)

        return query


class MLP(BaseModule):
    """Very simple multi-layer perceptron (also called FFN) with relu. Mostly
    used in DETR series detectors.

    Args:
        input_dim (int): Feature dim of the input tensor.
        hidden_dim (int): Feature dim of the hidden layer.
        output_dim (int): Feature dim of the output tensor.
        num_layers (int): Number of FFN layers. As the last
            layer of MLP only contains FFN (Linear).
    """

    def __init__(self, input_dim: int, hidden_dim: int, output_dim: int,
                 num_layers: int) -> None:
        super().__init__()
        self.num_layers = num_layers
        h = [hidden_dim] * (num_layers - 1)
        self.layers = ModuleList(
            Linear(n, k) for n, k in zip([input_dim] + h, h + [output_dim]))

    def forward(self, x: Tensor) -> Tensor:
        """Forward function of MLP.

        Args:
            x (Tensor): The input feature, has shape
                (num_queries, bs, input_dim).
        Returns:
            Tensor: The output feature, has shape
                (num_queries, bs, output_dim).
        """
        for i, layer in enumerate(self.layers):
            x = F.relu(layer(x)) if i < self.num_layers - 1 else layer(x)
        return x


@MODELS.register_module()
class DynamicConv(BaseModule):
    """Implements Dynamic Convolution.

    This module generate parameters for each sample and
    use bmm to implement 1*1 convolution. Code is modified
    from the `official github repo <https://github.com/PeizeSun/
    SparseR-CNN/blob/main/projects/SparseRCNN/sparsercnn/head.py#L258>`_ .

    Args:
        in_channels (int): The input feature channel.
            Defaults to 256.
        feat_channels (int): The inner feature channel.
            Defaults to 64.
        out_channels (int, optional): The output feature channel.
            When not specified, it will be set to `in_channels`
            by default
        input_feat_shape (int): The shape of input feature.
            Defaults to 7.
        with_proj (bool): Project two-dimentional feature to
            one-dimentional feature. Default to True.
        act_cfg (dict): The activation config for DynamicConv.
        norm_cfg (dict): Config dict for normalization layer. Default
            layer normalization.
        init_cfg (obj:`mmengine.ConfigDict`): The Config for initialization.
            Default: None.
    """

    def __init__(self,
                 in_channels: int = 256,
                 feat_channels: int = 64,
                 out_channels: Optional[int] = None,
                 input_feat_shape: int = 7,
                 with_proj: bool = True,
                 act_cfg: OptConfigType = dict(type='ReLU', inplace=True),
                 norm_cfg: OptConfigType = dict(type='LN'),
                 init_cfg: OptConfigType = None) -> None:
        super(DynamicConv, self).__init__(init_cfg)
        self.in_channels = in_channels
        self.feat_channels = feat_channels
        self.out_channels_raw = out_channels
        self.input_feat_shape = input_feat_shape
        self.with_proj = with_proj
        self.act_cfg = act_cfg
        self.norm_cfg = norm_cfg
        self.out_channels = out_channels if out_channels else in_channels

        self.num_params_in = self.in_channels * self.feat_channels
        self.num_params_out = self.out_channels * self.feat_channels
        self.dynamic_layer = nn.Linear(
            self.in_channels, self.num_params_in + self.num_params_out)

        self.norm_in = build_norm_layer(norm_cfg, self.feat_channels)[1]
        self.norm_out = build_norm_layer(norm_cfg, self.out_channels)[1]

        self.activation = build_activation_layer(act_cfg)

        num_output = self.out_channels * input_feat_shape**2
        if self.with_proj:
            self.fc_layer = nn.Linear(num_output, self.out_channels)
            self.fc_norm = build_norm_layer(norm_cfg, self.out_channels)[1]

    def forward(self, param_feature: Tensor, input_feature: Tensor) -> Tensor:
        """Forward function for `DynamicConv`.

        Args:
            param_feature (Tensor): The feature can be used
                to generate the parameter, has shape
                (num_all_proposals, in_channels).
            input_feature (Tensor): Feature that
                interact with parameters, has shape
                (num_all_proposals, in_channels, H, W).

        Returns:
            Tensor: The output feature has shape
            (num_all_proposals, out_channels).
        """
        input_feature = input_feature.flatten(2).permute(2, 0, 1)

        input_feature = input_feature.permute(1, 0, 2)
        parameters = self.dynamic_layer(param_feature)

        param_in = parameters[:, :self.num_params_in].view(
            -1, self.in_channels, self.feat_channels)
        param_out = parameters[:, -self.num_params_out:].view(
            -1, self.feat_channels, self.out_channels)

        # input_feature has shape (num_all_proposals, H*W, in_channels)
        # param_in has shape (num_all_proposals, in_channels, feat_channels)
        # feature has shape (num_all_proposals, H*W, feat_channels)
        features = torch.bmm(input_feature, param_in)
        features = self.norm_in(features)
        features = self.activation(features)

        # param_out has shape (batch_size, feat_channels, out_channels)
        features = torch.bmm(features, param_out)
        features = self.norm_out(features)
        features = self.activation(features)

        if self.with_proj:
            features = features.flatten(1)
            features = self.fc_layer(features)
            features = self.fc_norm(features)
            features = self.activation(features)

        return features