detrsmpl/models/utils/transformer.py

# Copyright (c) OpenMMLab. All rights reserved.
import math
import warnings

import torch
import torch.nn as nn
from mmcv.cnn.bricks.registry import (
    TRANSFORMER_LAYER,
    TRANSFORMER_LAYER_SEQUENCE,
)
from mmcv.cnn.bricks.transformer import (
    BaseTransformerLayer,
    TransformerLayerSequence,
    build_transformer_layer_sequence,
)
from mmcv.runner.base_module import BaseModule
# from mmcv.utils import to_2tuple
from torch.nn.init import normal_

# from mmdet.models.utils.builder import TRANSFORMER
from .builder import TRANSFORMER

# import torch.nn.functional as F
from mmcv.cnn import (  # build_activation_layer,; build_conv_layer,
    build_norm_layer, xavier_init,
)

# from typing import Sequence

try:
    from mmcv.ops.multi_scale_deform_attn import MultiScaleDeformableAttention

except ImportError:
    warnings.warn(
        '`MultiScaleDeformableAttention` in MMCV has been moved to '
        '`mmcv.ops.multi_scale_deform_attn`, please update your MMCV')
    from mmcv.cnn.bricks.transformer import MultiScaleDeformableAttention


def inverse_sigmoid(x, eps=1e-5):
    """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 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)


@TRANSFORMER_LAYER.register_module()
class DetrTransformerDecoderLayer(BaseTransformerLayer):
    """Implements decoder layer in DETR transformer.

    Args:
        attn_cfgs (list[`mmcv.ConfigDict`] | list[dict] | dict )):
            Configs for self_attention or cross_attention, the order
            should be consistent with it in `operation_order`. If it is
            a dict, it would be expand to the number of attention in
            `operation_order`.
        feedforward_channels (int): The hidden dimension for FFNs.
        ffn_dropout (float): Probability of an element to be zeroed
            in ffn. Default 0.0.
        operation_order (tuple[str]): The execution order of operation
            in transformer. Such as ('self_attn', 'norm', 'ffn', 'norm').
            Default：None
        act_cfg (dict): The activation config for FFNs. Default: `LN`
        norm_cfg (dict): Config dict for normalization layer.
            Default: `LN`.
        ffn_num_fcs (int): The number of fully-connected layers in FFNs.
            Default：2.
    """
    def __init__(self,
                 attn_cfgs,
                 feedforward_channels,
                 ffn_dropout=0.0,
                 operation_order=None,
                 act_cfg=dict(type='ReLU', inplace=True),
                 norm_cfg=dict(type='LN'),
                 ffn_num_fcs=2,
                 **kwargs):
        super(DetrTransformerDecoderLayer,
              self).__init__(attn_cfgs=attn_cfgs,
                             feedforward_channels=feedforward_channels,
                             ffn_dropout=ffn_dropout,
                             operation_order=operation_order,
                             act_cfg=act_cfg,
                             norm_cfg=norm_cfg,
                             ffn_num_fcs=ffn_num_fcs,
                             **kwargs)
        assert len(operation_order) == 6
        assert set(operation_order) == set(
            ['self_attn', 'norm', 'cross_attn', 'ffn'])


@TRANSFORMER_LAYER_SEQUENCE.register_module()
class DetrTransformerEncoder(TransformerLayerSequence):
    """TransformerEncoder of DETR.

    Args:
        post_norm_cfg (dict): Config of last normalization layer. Default：
            `LN`. Only used when `self.pre_norm` is `True`
    """
    def __init__(self, *args, post_norm_cfg=dict(type='LN'), **kwargs):
        super(DetrTransformerEncoder, self).__init__(*args, **kwargs)
        if post_norm_cfg is not None:
            self.post_norm = build_norm_layer(
                post_norm_cfg, self.embed_dims)[1] if self.pre_norm else None
        else:
            assert not self.pre_norm, f'Use prenorm in ' \
                                      f'{self.__class__.__name__},' \
                                      f'Please specify post_norm_cfg'
            self.post_norm = None

    def forward(self, *args, **kwargs):
        """Forward function for `TransformerCoder`.

        Returns:
            Tensor: forwarded results with shape [num_query, bs, embed_dims].
        """
        x = super(DetrTransformerEncoder, self).forward(*args, **kwargs)
        if self.post_norm is not None:
            x = self.post_norm(x)
        return x


@TRANSFORMER_LAYER_SEQUENCE.register_module()
class DetrTransformerDecoder(TransformerLayerSequence):
    """Implements the decoder in DETR transformer.

    Args:
        return_intermediate (bool): Whether to return intermediate outputs.
        post_norm_cfg (dict): Config of last normalization layer. Default：
            `LN`.
    """
    def __init__(self,
                 *args,
                 post_norm_cfg=dict(type='LN'),
                 return_intermediate=False,
                 **kwargs):

        super(DetrTransformerDecoder, self).__init__(*args, **kwargs)
        self.return_intermediate = return_intermediate
        if post_norm_cfg is not None:
            self.post_norm = build_norm_layer(post_norm_cfg,
                                              self.embed_dims)[1]
        else:
            self.post_norm = None

    def forward(self, query, *args, **kwargs):
        """Forward function for `TransformerDecoder`.

        Args:
            query (Tensor): Input query with shape
                `(num_query, bs, embed_dims)`.

        Returns:
            Tensor: Results with shape [1, num_query, bs, embed_dims] when
                return_intermediate is `False`, otherwise it has shape
                [num_layers, num_query, bs, embed_dims].
        """
        if not self.return_intermediate:
            x = super().forward(query, *args, **kwargs)
            if self.post_norm:
                x = self.post_norm(x)[None]
            return x

        intermediate = []
        for layer in self.layers:
            query = layer(query, *args, **kwargs)
            if self.return_intermediate:
                if self.post_norm is not None:
                    intermediate.append(self.post_norm(query))
                else:
                    intermediate.append(query)
        return torch.stack(intermediate)


@TRANSFORMER_LAYER_SEQUENCE.register_module()
class DeformableDetrTransformerDecoder(TransformerLayerSequence):
    """Implements the decoder in DETR transformer.

    Args:
        return_intermediate (bool): Whether to return intermediate outputs.
        coder_norm_cfg (dict): Config of last normalization layer. Default：
            `LN`.
    """
    def __init__(self, *args, return_intermediate=False, **kwargs):

        super(DeformableDetrTransformerDecoder, self).__init__(*args, **kwargs)
        self.return_intermediate = return_intermediate

    def forward(self,
                query,
                *args,
                reference_points=None,
                valid_ratios=None,
                reg_branches=None,
                **kwargs):
        """Forward function for `TransformerDecoder`.

        Args:
            query (Tensor): Input query with shape
                `(num_query, bs, embed_dims)`.
            reference_points (Tensor): The reference
                points of offset. has shape
                (bs, num_query, 4) when as_two_stage,
                otherwise has shape ((bs, num_query, 2).
            valid_ratios (Tensor): The radios of valid
                points on the feature map, has shape
                (bs, num_levels, 2)
            reg_branch: (obj:`nn.ModuleList`): Used for
                refining the regression results. Only would
                be passed when with_box_refine is True,
                otherwise would be passed a `None`.

        Returns:
            Tensor: Results with shape [1, num_query, bs, embed_dims] when
                return_intermediate is `False`, otherwise it has shape
                [num_layers, num_query, bs, embed_dims].
        """
        output = query
        intermediate = []
        intermediate_reference_points = []
        for lid, layer in enumerate(self.layers):
            if reference_points.shape[-1] == 4:
                reference_points_input = reference_points[:, :, None] * \
                    torch.cat([valid_ratios, valid_ratios], -1)[:, None]
            else:
                assert reference_points.shape[-1] == 2
                reference_points_input = reference_points[:, :, None] * \
                    valid_ratios[:, None]
            output = layer(output,
                           *args,
                           reference_points=reference_points_input,
                           **kwargs)
            output = output.permute(1, 0, 2)

            if reg_branches is not None:
                tmp = reg_branches[lid](output)
                if reference_points.shape[-1] == 4:
                    new_reference_points = tmp + inverse_sigmoid(
                        reference_points)
                    new_reference_points = new_reference_points.sigmoid()
                else:
                    assert reference_points.shape[-1] == 2
                    new_reference_points = tmp
                    new_reference_points[..., :2] = tmp[
                        ..., :2] + inverse_sigmoid(reference_points)
                    new_reference_points = new_reference_points.sigmoid()
                reference_points = new_reference_points.detach()

            output = output.permute(1, 0, 2)
            if self.return_intermediate:
                intermediate.append(output)
                intermediate_reference_points.append(reference_points)

        if self.return_intermediate:
            return torch.stack(intermediate), torch.stack(
                intermediate_reference_points)

        return output, reference_points


@TRANSFORMER.register_module()
class Transformer(BaseModule):
    """Implements the DETR transformer.

    Following the official DETR implementation, this module copy-paste
    from torch.nn.Transformer with modifications:

        * positional encodings are passed in MultiheadAttention
        * extra LN at the end of encoder is removed
        * decoder returns a stack of activations from all decoding layers

    See `paper: End-to-End Object Detection with Transformers
    <https://arxiv.org/pdf/2005.12872>`_ for details.

    Args:
        encoder (`mmcv.ConfigDict` | Dict): Config of
            TransformerEncoder. Defaults to None.
        decoder ((`mmcv.ConfigDict` | Dict)): Config of
            TransformerDecoder. Defaults to None
        init_cfg (obj:`mmcv.ConfigDict`): The Config for initialization.
            Defaults to None.
    """
    def __init__(self, encoder=None, decoder=None, init_cfg=None):
        super(Transformer, self).__init__(init_cfg=init_cfg)
        self.encoder = build_transformer_layer_sequence(encoder)
        self.decoder = build_transformer_layer_sequence(decoder)
        self.embed_dims = self.encoder.embed_dims

    def init_weights(self):
        # follow the official DETR to init parameters
        for m in self.modules():
            if hasattr(m, 'weight') and m.weight.dim() > 1:
                xavier_init(m, distribution='uniform')
        self._is_init = True

    def forward(self, x, mask, query_embed, pos_embed):
        """Forward function for `Transformer`.

        Args:
            x (Tensor): Input query with shape [bs, c, h, w] where
                c = embed_dims.
            mask (Tensor): The key_padding_mask used for encoder and decoder,
                with shape [bs, h, w].
            query_embed (Tensor): The query embedding for decoder, with shape
                [num_query, c].
            pos_embed (Tensor): The positional encoding for encoder and
                decoder, with the same shape as `x`.

        Returns:
            tuple[Tensor]: results of decoder containing the following tensor.

                - out_dec: Output from decoder. If return_intermediate_dec \
                      is True output has shape [num_dec_layers, bs,
                      num_query, embed_dims], else has shape [1, bs, \
                      num_query, embed_dims].
                - memory: Output results from encoder, with shape \
                      [bs, embed_dims, h, w].
        """
        bs, c, h, w = x.shape
        # use `view` instead of `flatten` for dynamically exporting to ONNX
        x = x.view(bs, c, -1).permute(2, 0, 1)  # [bs, c, h, w] -> [h*w, bs, c]
        pos_embed = pos_embed.view(bs, c, -1).permute(2, 0, 1)
        query_embed = query_embed.unsqueeze(1).repeat(
            1, bs, 1)  # [num_query, dim] -> [num_query, bs, dim]
        mask = mask.view(bs, -1)  # [bs, h, w] -> [bs, h*w]
        memory = self.encoder(query=x,
                              key=None,
                              value=None,
                              query_pos=pos_embed,
                              query_key_padding_mask=mask)
        target = torch.zeros_like(query_embed)
        # out_dec: [num_layers, num_query, bs, dim]
        out_dec = self.decoder(query=target,
                               key=memory,
                               value=memory,
                               key_pos=pos_embed,
                               query_pos=query_embed,
                               key_padding_mask=mask)
        out_dec = out_dec.transpose(1, 2)
        memory = memory.permute(1, 2, 0).reshape(bs, c, h, w)
        return out_dec, memory


@TRANSFORMER.register_module()
class DeformableDetrTransformer(Transformer):
    """Implements the DeformableDETR transformer.

    Args:
        as_two_stage (bool): Generate query from encoder features.
            Default: False.
        num_feature_levels (int): Number of feature maps from FPN:
            Default: 4.
        two_stage_num_proposals (int): Number of proposals when set
            `as_two_stage` as True. Default: 300.
    """
    def __init__(self,
                 as_two_stage=False,
                 num_feature_levels=4,
                 two_stage_num_proposals=300,
                 **kwargs):
        super(DeformableDetrTransformer, self).__init__(**kwargs)
        self.as_two_stage = as_two_stage
        self.num_feature_levels = num_feature_levels
        self.two_stage_num_proposals = two_stage_num_proposals
        self.embed_dims = self.encoder.embed_dims
        self.init_layers()

    def init_layers(self):
        """Initialize layers of the DeformableDetrTransformer."""
        self.level_embeds = nn.Parameter(
            torch.Tensor(self.num_feature_levels, self.embed_dims))

        if self.as_two_stage:
            self.enc_output = nn.Linear(self.embed_dims, self.embed_dims)
            self.enc_output_norm = nn.LayerNorm(self.embed_dims)
            self.pos_trans = nn.Linear(self.embed_dims * 2,
                                       self.embed_dims * 2)
            self.pos_trans_norm = nn.LayerNorm(self.embed_dims * 2)
        else:
            self.reference_points = nn.Linear(self.embed_dims, 2)

    def init_weights(self):
        """Initialize the transformer weights."""
        for p in self.parameters():
            if p.dim() > 1:
                nn.init.xavier_uniform_(p)
        for m in self.modules():
            if isinstance(m, MultiScaleDeformableAttention):
                m.init_weights()
        if not self.as_two_stage:
            xavier_init(self.reference_points, distribution='uniform', bias=0.)
        normal_(self.level_embeds)

    def gen_encoder_output_proposals(self, memory, memory_padding_mask,
                                     spatial_shapes):
        """Generate proposals from encoded memory.

        Args:
            memory (Tensor) : The output of encoder,
                has shape (bs, num_key, embed_dim).  num_key is
                equal the number of points on feature map from
                all level.
            memory_padding_mask (Tensor): Padding mask for memory.
                has shape (bs, num_key).
            spatial_shapes (Tensor): The shape of all feature maps.
                has shape (num_level, 2).

        Returns:
            tuple: A tuple of feature map and bbox prediction.

                - output_memory (Tensor): The input of decoder,  \
                    has shape (bs, num_key, embed_dim).  num_key is \
                    equal the number of points on feature map from \
                    all levels.
                - output_proposals (Tensor): The normalized proposal \
                    after a inverse sigmoid, has shape \
                    (bs, num_keys, 4).
        """

        N, S, C = memory.shape
        proposals = []
        _cur = 0
        for lvl, (H, W) in enumerate(spatial_shapes):
            mask_flatten_ = memory_padding_mask[:, _cur:(_cur + H * W)].view(
                N, H, W, 1)
            valid_H = torch.sum(~mask_flatten_[:, :, 0, 0], 1)
            valid_W = torch.sum(~mask_flatten_[:, 0, :, 0], 1)

            grid_y, grid_x = torch.meshgrid(
                torch.linspace(0,
                               H - 1,
                               H,
                               dtype=torch.float32,
                               device=memory.device),
                torch.linspace(0,
                               W - 1,
                               W,
                               dtype=torch.float32,
                               device=memory.device))
            grid = torch.cat([grid_x.unsqueeze(-1), grid_y.unsqueeze(-1)], -1)

            scale = torch.cat([valid_W.unsqueeze(-1),
                               valid_H.unsqueeze(-1)], 1).view(N, 1, 1, 2)
            grid = (grid.unsqueeze(0).expand(N, -1, -1, -1) + 0.5) / scale
            wh = torch.ones_like(grid) * 0.05 * (2.0**lvl)
            proposal = torch.cat((grid, wh), -1).view(N, -1, 4)
            proposals.append(proposal)
            _cur += (H * W)
        output_proposals = torch.cat(proposals, 1)
        output_proposals_valid = ((output_proposals > 0.01) &
                                  (output_proposals < 0.99)).all(-1,
                                                                 keepdim=True)
        output_proposals = torch.log(output_proposals / (1 - output_proposals))
        output_proposals = output_proposals.masked_fill(
            memory_padding_mask.unsqueeze(-1), float('inf'))
        output_proposals = output_proposals.masked_fill(
            ~output_proposals_valid, float('inf'))

        output_memory = memory
        output_memory = output_memory.masked_fill(
            memory_padding_mask.unsqueeze(-1), float(0))
        output_memory = output_memory.masked_fill(~output_proposals_valid,
                                                  float(0))
        output_memory = self.enc_output_norm(self.enc_output(output_memory))
        return output_memory, output_proposals

    @staticmethod
    def get_reference_points(spatial_shapes, valid_ratios, device):
        """Get the reference points used in decoder.

        Args:
            spatial_shapes (Tensor): The shape of all
                feature maps, has shape (num_level, 2).
            valid_ratios (Tensor): The radios of valid
                points on the feature map, has shape
                (bs, num_levels, 2)
            device (obj:`device`): The device where
                reference_points should be.

        Returns:
            Tensor: reference points used in decoder, has \
                shape (bs, num_keys, num_levels, 2).
        """
        reference_points_list = []
        for lvl, (H, W) in enumerate(spatial_shapes):
            #  TODO  check this 0.5
            ref_y, ref_x = torch.meshgrid(
                torch.linspace(0.5,
                               H - 0.5,
                               H,
                               dtype=torch.float32,
                               device=device),
                torch.linspace(0.5,
                               W - 0.5,
                               W,
                               dtype=torch.float32,
                               device=device))
            ref_y = ref_y.reshape(-1)[None] / (valid_ratios[:, None, lvl, 1] *
                                               H)
            ref_x = ref_x.reshape(-1)[None] / (valid_ratios[:, None, lvl, 0] *
                                               W)
            ref = torch.stack((ref_x, ref_y), -1)
            reference_points_list.append(ref)
        reference_points = torch.cat(reference_points_list, 1)
        reference_points = reference_points[:, :, None] * valid_ratios[:, None]
        return reference_points

    def get_valid_ratio(self, mask):
        """Get the valid radios of feature maps of all  level."""
        _, H, W = mask.shape
        valid_H = torch.sum(~mask[:, :, 0], 1)
        valid_W = torch.sum(~mask[:, 0, :], 1)
        valid_ratio_h = valid_H.float() / H
        valid_ratio_w = valid_W.float() / W
        valid_ratio = torch.stack([valid_ratio_w, valid_ratio_h], -1)
        return valid_ratio

    def get_proposal_pos_embed(self,
                               proposals,
                               num_pos_feats=128,
                               temperature=10000):
        """Get the position embedding of proposal."""
        scale = 2 * math.pi
        dim_t = torch.arange(num_pos_feats,
                             dtype=torch.float32,
                             device=proposals.device)
        dim_t = temperature**(2 * (dim_t // 2) / num_pos_feats)
        # N, L, 4
        proposals = proposals.sigmoid() * scale
        # N, L, 4, 128
        pos = proposals[:, :, :, None] / dim_t
        # N, L, 4, 64, 2
        pos = torch.stack((pos[:, :, :, 0::2].sin(), pos[:, :, :, 1::2].cos()),
                          dim=4).flatten(2)
        return pos

    def forward(self,
                mlvl_feats,
                mlvl_masks,
                query_embed,
                mlvl_pos_embeds,
                reg_branches=None,
                cls_branches=None,
                smpl_branches=None,
                **kwargs):
        """Forward function for `Transformer`.

        Args:
            mlvl_feats (list(Tensor)): Input queries from
                different level. Each element has shape
                [bs, embed_dims, h, w].
            mlvl_masks (list(Tensor)): The key_padding_mask from
                different level used for encoder and decoder,
                each element has shape  [bs, h, w].
            query_embed (Tensor): The query embedding for decoder,
                with shape [num_query, c].
            mlvl_pos_embeds (list(Tensor)): The positional encoding
                of feats from different level, has the shape
                 [bs, embed_dims, h, w].
            reg_branches (obj:`nn.ModuleList`): Regression heads for
                feature maps from each decoder layer. Only would
                be passed when
                `with_box_refine` is True. Default to None.
            cls_branches (obj:`nn.ModuleList`): Classification heads
                for feature maps from each decoder layer. Only would
                 be passed when `as_two_stage`
                 is True. Default to None.


        Returns:
            tuple[Tensor]: results of decoder containing the following tensor.

                - inter_states: Outputs from decoder. If
                    return_intermediate_dec is True output has shape \
                      (num_dec_layers, bs, num_query, embed_dims), else has \
                      shape (1, bs, num_query, embed_dims).
                - init_reference_out: The initial value of reference \
                    points, has shape (bs, num_queries, 4).
                - inter_references_out: The internal value of reference \
                    points in decoder, has shape \
                    (num_dec_layers, bs,num_query, embed_dims)
                - enc_outputs_class: The classification score of \
                    proposals generated from \
                    encoder's feature maps, has shape \
                    (batch, h*w, num_classes). \
                    Only would be returned when `as_two_stage` is True, \
                    otherwise None.
                - enc_outputs_coord_unact: The regression results \
                    generated from encoder's feature maps., has shape \
                    (batch, h*w, 4). Only would \
                    be returned when `as_two_stage` is True, \
                    otherwise None.
        """
        assert self.as_two_stage or query_embed is not None

        feat_flatten = []
        mask_flatten = []
        lvl_pos_embed_flatten = []
        spatial_shapes = []
        for lvl, (feat, mask, pos_embed) in enumerate(
                zip(mlvl_feats, mlvl_masks, mlvl_pos_embeds)):
            bs, c, h, w = feat.shape
            spatial_shape = (h, w)
            spatial_shapes.append(spatial_shape)
            feat = feat.flatten(2).transpose(1, 2)
            mask = mask.flatten(1)
            pos_embed = pos_embed.flatten(2).transpose(1, 2)
            lvl_pos_embed = pos_embed + self.level_embeds[lvl].view(1, 1, -1)
            lvl_pos_embed_flatten.append(lvl_pos_embed)
            feat_flatten.append(feat)
            mask_flatten.append(mask)
        feat_flatten = torch.cat(feat_flatten, 1)
        mask_flatten = torch.cat(mask_flatten, 1)
        lvl_pos_embed_flatten = torch.cat(lvl_pos_embed_flatten, 1)
        spatial_shapes = torch.as_tensor(spatial_shapes,
                                         dtype=torch.long,
                                         device=feat_flatten.device)
        level_start_index = torch.cat((spatial_shapes.new_zeros(
            (1, )), spatial_shapes.prod(1).cumsum(0)[:-1]))
        valid_ratios = torch.stack(
            [self.get_valid_ratio(m) for m in mlvl_masks], 1)

        reference_points = \
            self.get_reference_points(spatial_shapes,
                                      valid_ratios,
                                      device=feat.device)

        feat_flatten = feat_flatten.permute(1, 0, 2)  # (H*W, bs, embed_dims)
        lvl_pos_embed_flatten = lvl_pos_embed_flatten.permute(
            1, 0, 2)  # (H*W, bs, embed_dims)
        memory = self.encoder(query=feat_flatten,
                              key=None,
                              value=None,
                              query_pos=lvl_pos_embed_flatten,
                              query_key_padding_mask=mask_flatten,
                              spatial_shapes=spatial_shapes,
                              reference_points=reference_points,
                              level_start_index=level_start_index,
                              valid_ratios=valid_ratios,
                              **kwargs)

        memory = memory.permute(1, 0, 2)
        bs, _, c = memory.shape
        if self.as_two_stage:
            output_memory, output_proposals = \
                self.gen_encoder_output_proposals(
                    memory, mask_flatten, spatial_shapes)
            enc_outputs_class = cls_branches[self.decoder.num_layers](
                output_memory)
            enc_outputs_coord_unact = \
                reg_branches[
                    self.decoder.num_layers](output_memory) + output_proposals

            topk = self.two_stage_num_proposals
            # We only use the first channel in enc_outputs_class as foreground,
            # the other (num_classes - 1) channels are actually not used.
            # Its targets are set to be 0s, which indicates the first
            # class (foreground) because we use [0, num_classes - 1] to
            # indicate class labels, background class is indicated by
            # num_classes (similar convention in RPN).
            # See https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/dense_heads/deformable_detr_head.py#L241 # noqa
            # This follows the official implementation of Deformable DETR.
            topk_proposals = torch.topk(enc_outputs_class[..., 0], topk,
                                        dim=1)[1]
            topk_coords_unact = torch.gather(
                enc_outputs_coord_unact, 1,
                topk_proposals.unsqueeze(-1).repeat(1, 1, 4))
            topk_coords_unact = topk_coords_unact.detach()
            reference_points = topk_coords_unact.sigmoid()
            init_reference_out = reference_points
            pos_trans_out = self.pos_trans_norm(
                self.pos_trans(self.get_proposal_pos_embed(topk_coords_unact)))
            query_pos, query = torch.split(pos_trans_out, c, dim=2)
        else:
            query_pos, query = torch.split(query_embed, c, dim=1)
            query_pos = query_pos.unsqueeze(0).expand(bs, -1, -1)
            query = query.unsqueeze(0).expand(bs, -1, -1)
            reference_points = self.reference_points(query_pos).sigmoid()
            init_reference_out = reference_points

        # decoder
        query = query.permute(1, 0, 2)
        memory = memory.permute(1, 0, 2)
        query_pos = query_pos.permute(1, 0, 2)
        inter_states, inter_references = self.decoder(
            query=query,
            key=None,
            value=memory,
            query_pos=query_pos,
            key_padding_mask=mask_flatten,
            reference_points=reference_points,
            spatial_shapes=spatial_shapes,
            level_start_index=level_start_index,
            valid_ratios=valid_ratios,
            reg_branches=reg_branches,
            smpl_branches=smpl_branches,
            **kwargs)

        inter_references_out = inter_references
        if self.as_two_stage:
            return inter_states, init_reference_out,\
                inter_references_out, enc_outputs_class,\
                enc_outputs_coord_unact
        return inter_states, init_reference_out, \
            inter_references_out, None, None