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Source code for mmcv.ops.deform_conv

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

import torch
import torch.nn as nn
import torch.nn.functional as F
from torch import Tensor
from torch.autograd import Function
from torch.autograd.function import once_differentiable
from torch.nn.modules.utils import _pair, _single

from mmcv.utils import deprecated_api_warning
from ..cnn import CONV_LAYERS
from ..utils import ext_loader, print_log

ext_module = ext_loader.load_ext('_ext', [
    'deform_conv_forward', 'deform_conv_backward_input',
    'deform_conv_backward_parameters'
])


class DeformConv2dFunction(Function):

    @staticmethod
    def symbolic(g,
                 input,
                 offset,
                 weight,
                 stride,
                 padding,
                 dilation,
                 groups,
                 deform_groups,
                 bias=False,
                 im2col_step=32):
        return g.op(
            'mmcv::MMCVDeformConv2d',
            input,
            offset,
            weight,
            stride_i=stride,
            padding_i=padding,
            dilation_i=dilation,
            groups_i=groups,
            deform_groups_i=deform_groups,
            bias_i=bias,
            im2col_step_i=im2col_step)

    @staticmethod
    def forward(ctx,
                input: Tensor,
                offset: Tensor,
                weight: Tensor,
                stride: Union[int, Tuple[int, ...]] = 1,
                padding: Union[int, Tuple[int, ...]] = 0,
                dilation: Union[int, Tuple[int, ...]] = 1,
                groups: int = 1,
                deform_groups: int = 1,
                bias: bool = False,
                im2col_step: int = 32) -> Tensor:
        if input is not None and input.dim() != 4:
            raise ValueError(
                f'Expected 4D tensor as input, got {input.dim()}D tensor \
                  instead.')
        assert bias is False, 'Only support bias is False.'
        ctx.stride = _pair(stride)
        ctx.padding = _pair(padding)
        ctx.dilation = _pair(dilation)
        ctx.groups = groups
        ctx.deform_groups = deform_groups
        ctx.im2col_step = im2col_step

        # When pytorch version >= 1.6.0, amp is adopted for fp16 mode;
        # amp won't cast the type of model (float32), but "offset" is cast
        # to float16 by nn.Conv2d automatically, leading to the type
        # mismatch with input (when it is float32) or weight.
        # The flag for whether to use fp16 or amp is the type of "offset",
        # we cast weight and input to temporarily support fp16 and amp
        # whatever the pytorch version is.
        input = input.type_as(offset)
        weight = weight.type_as(input)
        ctx.save_for_backward(input, offset, weight)

        output = input.new_empty(
            DeformConv2dFunction._output_size(ctx, input, weight))

        ctx.bufs_ = [input.new_empty(0), input.new_empty(0)]  # columns, ones

        cur_im2col_step = min(ctx.im2col_step, input.size(0))
        assert (input.size(0) % cur_im2col_step
                ) == 0, 'batch size must be divisible by im2col_step'
        ext_module.deform_conv_forward(
            input,
            weight,
            offset,
            output,
            ctx.bufs_[0],
            ctx.bufs_[1],
            kW=weight.size(3),
            kH=weight.size(2),
            dW=ctx.stride[1],
            dH=ctx.stride[0],
            padW=ctx.padding[1],
            padH=ctx.padding[0],
            dilationW=ctx.dilation[1],
            dilationH=ctx.dilation[0],
            group=ctx.groups,
            deformable_group=ctx.deform_groups,
            im2col_step=cur_im2col_step)
        return output

    @staticmethod
    @once_differentiable
    def backward(
        ctx, grad_output: Tensor
    ) -> Tuple[Optional[Tensor], Optional[Tensor], Optional[Tensor], None,
               None, None, None, None, None, None]:
        input, offset, weight = ctx.saved_tensors

        grad_input = grad_offset = grad_weight = None

        cur_im2col_step = min(ctx.im2col_step, input.size(0))
        assert (input.size(0) % cur_im2col_step
                ) == 0, 'batch size must be divisible by im2col_step'

        grad_output = grad_output.contiguous()
        if ctx.needs_input_grad[0] or ctx.needs_input_grad[1]:
            grad_input = torch.zeros_like(input)
            grad_offset = torch.zeros_like(offset)
            ext_module.deform_conv_backward_input(
                input,
                offset,
                grad_output,
                grad_input,
                grad_offset,
                weight,
                ctx.bufs_[0],
                kW=weight.size(3),
                kH=weight.size(2),
                dW=ctx.stride[1],
                dH=ctx.stride[0],
                padW=ctx.padding[1],
                padH=ctx.padding[0],
                dilationW=ctx.dilation[1],
                dilationH=ctx.dilation[0],
                group=ctx.groups,
                deformable_group=ctx.deform_groups,
                im2col_step=cur_im2col_step)

        if ctx.needs_input_grad[2]:
            grad_weight = torch.zeros_like(weight)
            ext_module.deform_conv_backward_parameters(
                input,
                offset,
                grad_output,
                grad_weight,
                ctx.bufs_[0],
                ctx.bufs_[1],
                kW=weight.size(3),
                kH=weight.size(2),
                dW=ctx.stride[1],
                dH=ctx.stride[0],
                padW=ctx.padding[1],
                padH=ctx.padding[0],
                dilationW=ctx.dilation[1],
                dilationH=ctx.dilation[0],
                group=ctx.groups,
                deformable_group=ctx.deform_groups,
                scale=1,
                im2col_step=cur_im2col_step)

        return grad_input, grad_offset, grad_weight, \
            None, None, None, None, None, None, None

    @staticmethod
    def _output_size(ctx, input, weight):
        channels = weight.size(0)
        output_size = (input.size(0), channels)
        for d in range(input.dim() - 2):
            in_size = input.size(d + 2)
            pad = ctx.padding[d]
            kernel = ctx.dilation[d] * (weight.size(d + 2) - 1) + 1
            stride_ = ctx.stride[d]
            output_size += ((in_size + (2 * pad) - kernel) // stride_ + 1, )
        if not all(map(lambda s: s > 0, output_size)):
            raise ValueError(
                'convolution input is too small (output would be ' +
                'x'.join(map(str, output_size)) + ')')
        return output_size


deform_conv2d = DeformConv2dFunction.apply


[docs]class DeformConv2d(nn.Module): r"""Deformable 2D convolution. Applies a deformable 2D convolution over an input signal composed of several input planes. DeformConv2d was described in the paper `Deformable Convolutional Networks <https://arxiv.org/pdf/1703.06211.pdf>`_ Note: The argument ``im2col_step`` was added in version 1.3.17, which means number of samples processed by the ``im2col_cuda_kernel`` per call. It enables users to define ``batch_size`` and ``im2col_step`` more flexibly and solved `issue mmcv#1440 <https://github.com/open-mmlab/mmcv/issues/1440>`_. Args: in_channels (int): Number of channels in the input image. out_channels (int): Number of channels produced by the convolution. kernel_size(int, tuple): Size of the convolving kernel. stride(int, tuple): Stride of the convolution. Default: 1. padding (int or tuple): Zero-padding added to both sides of the input. Default: 0. dilation (int or tuple): Spacing between kernel elements. Default: 1. groups (int): Number of blocked connections from input. channels to output channels. Default: 1. deform_groups (int): Number of deformable group partitions. bias (bool): If True, adds a learnable bias to the output. Default: False. im2col_step (int): Number of samples processed by im2col_cuda_kernel per call. It will work when ``batch_size`` > ``im2col_step``, but ``batch_size`` must be divisible by ``im2col_step``. Default: 32. `New in version 1.3.17.` """ @deprecated_api_warning({'deformable_groups': 'deform_groups'}, cls_name='DeformConv2d') def __init__(self, in_channels: int, out_channels: int, kernel_size: Union[int, Tuple[int, ...]], stride: Union[int, Tuple[int, ...]] = 1, padding: Union[int, Tuple[int, ...]] = 0, dilation: Union[int, Tuple[int, ...]] = 1, groups: int = 1, deform_groups: int = 1, bias: bool = False, im2col_step: int = 32) -> None: super().__init__() assert not bias, \ f'bias={bias} is not supported in DeformConv2d.' assert in_channels % groups == 0, \ f'in_channels {in_channels} cannot be divisible by groups {groups}' assert out_channels % groups == 0, \ f'out_channels {out_channels} cannot be divisible by groups \ {groups}' self.in_channels = in_channels self.out_channels = out_channels self.kernel_size = _pair(kernel_size) self.stride = _pair(stride) self.padding = _pair(padding) self.dilation = _pair(dilation) self.groups = groups self.deform_groups = deform_groups self.im2col_step = im2col_step # enable compatibility with nn.Conv2d self.transposed = False self.output_padding = _single(0) # only weight, no bias self.weight = nn.Parameter( torch.Tensor(out_channels, in_channels // self.groups, *self.kernel_size)) self.reset_parameters() def reset_parameters(self): # switch the initialization of `self.weight` to the standard kaiming # method described in `Delving deep into rectifiers: Surpassing # human-level performance on ImageNet classification` - He, K. et al. # (2015), using a uniform distribution nn.init.kaiming_uniform_(self.weight, nonlinearity='relu')
[docs] def forward(self, x: Tensor, offset: Tensor) -> Tensor: """Deformable Convolutional forward function. Args: x (Tensor): Input feature, shape (B, C_in, H_in, W_in) offset (Tensor): Offset for deformable convolution, shape (B, deform_groups*kernel_size[0]*kernel_size[1]*2, H_out, W_out), H_out, W_out are equal to the output's. An offset is like `[y0, x0, y1, x1, y2, x2, ..., y8, x8]`. The spatial arrangement is like: .. code:: text (x0, y0) (x1, y1) (x2, y2) (x3, y3) (x4, y4) (x5, y5) (x6, y6) (x7, y7) (x8, y8) Returns: Tensor: Output of the layer. """ # To fix an assert error in deform_conv_cuda.cpp:128 # input image is smaller than kernel input_pad = (x.size(2) < self.kernel_size[0]) or (x.size(3) < self.kernel_size[1]) if input_pad: pad_h = max(self.kernel_size[0] - x.size(2), 0) pad_w = max(self.kernel_size[1] - x.size(3), 0) x = F.pad(x, (0, pad_w, 0, pad_h), 'constant', 0).contiguous() offset = F.pad(offset, (0, pad_w, 0, pad_h), 'constant', 0) offset = offset.contiguous() out = deform_conv2d(x, offset, self.weight, self.stride, self.padding, self.dilation, self.groups, self.deform_groups, False, self.im2col_step) if input_pad: out = out[:, :, :out.size(2) - pad_h, :out.size(3) - pad_w].contiguous() return out
def __repr__(self): s = self.__class__.__name__ s += f'(in_channels={self.in_channels},\n' s += f'out_channels={self.out_channels},\n' s += f'kernel_size={self.kernel_size},\n' s += f'stride={self.stride},\n' s += f'padding={self.padding},\n' s += f'dilation={self.dilation},\n' s += f'groups={self.groups},\n' s += f'deform_groups={self.deform_groups},\n' # bias is not supported in DeformConv2d. s += 'bias=False)' return s
[docs]@CONV_LAYERS.register_module('DCN') class DeformConv2dPack(DeformConv2d): """A Deformable Conv Encapsulation that acts as normal Conv layers. The offset tensor is like `[y0, x0, y1, x1, y2, x2, ..., y8, x8]`. The spatial arrangement is like: .. code:: text (x0, y0) (x1, y1) (x2, y2) (x3, y3) (x4, y4) (x5, y5) (x6, y6) (x7, y7) (x8, y8) Args: in_channels (int): Same as nn.Conv2d. out_channels (int): Same as nn.Conv2d. kernel_size (int or tuple[int]): Same as nn.Conv2d. stride (int or tuple[int]): Same as nn.Conv2d. padding (int or tuple[int]): Same as nn.Conv2d. dilation (int or tuple[int]): Same as nn.Conv2d. groups (int): Same as nn.Conv2d. bias (bool or str): If specified as `auto`, it will be decided by the norm_cfg. Bias will be set as True if norm_cfg is None, otherwise False. """ _version = 2 def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.conv_offset = nn.Conv2d( self.in_channels, self.deform_groups * 2 * self.kernel_size[0] * self.kernel_size[1], kernel_size=self.kernel_size, stride=_pair(self.stride), padding=_pair(self.padding), dilation=_pair(self.dilation), bias=True) self.init_offset() def init_offset(self): self.conv_offset.weight.data.zero_() self.conv_offset.bias.data.zero_()
[docs] def forward(self, x: Tensor) -> Tensor: # type: ignore offset = self.conv_offset(x) return deform_conv2d(x, offset, self.weight, self.stride, self.padding, self.dilation, self.groups, self.deform_groups, False, self.im2col_step)
def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs): version = local_metadata.get('version', None) if version is None or version < 2: # the key is different in early versions # In version < 2, DeformConvPack loads previous benchmark models. if (prefix + 'conv_offset.weight' not in state_dict and prefix[:-1] + '_offset.weight' in state_dict): state_dict[prefix + 'conv_offset.weight'] = state_dict.pop( prefix[:-1] + '_offset.weight') if (prefix + 'conv_offset.bias' not in state_dict and prefix[:-1] + '_offset.bias' in state_dict): state_dict[prefix + 'conv_offset.bias'] = state_dict.pop(prefix[:-1] + '_offset.bias') if version is not None and version > 1: print_log( f'DeformConv2dPack {prefix.rstrip(".")} is upgraded to ' 'version 2.', logger='root') super()._load_from_state_dict(state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs)
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