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conv2d_helpers.py
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conv2d_helpers.py
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import torch
import torch.nn as nn
import torch.nn.functional as F
import math
def _is_static_pad(kernel_size, stride=1, dilation=1, **_):
return stride == 1 and (dilation * (kernel_size - 1)) % 2 == 0
def _get_padding(kernel_size, stride=1, dilation=1, **_):
padding = ((stride - 1) + dilation * (kernel_size - 1)) // 2
return padding
def _calc_same_pad(i, k, s, d):
return max((math.ceil(i / s) - 1) * s + (k - 1) * d + 1 - i, 0)
def _split_channels(num_chan, num_groups):
split = [num_chan // num_groups for _ in range(num_groups)]
split[0] += num_chan - sum(split)
return split
class ChannelToSpace(nn.Module):
def __init__(self, upscale_factor=2):
super().__init__()
self.bs = upscale_factor
def forward(self, x):
N, C, H, W = x.size()
x = x.view(N, self.bs, self.bs, C // (self.bs ** 2), H, W) # (N, bs, bs, C//bs^2, H, W)
x = x.permute(0, 3, 4, 1, 5, 2).contiguous() # (N, C//bs^2, H, bs, W, bs)
x = x.view(N, C // (self.bs ** 2), H * self.bs, W * self.bs) # (N, C//bs^2, H * bs, W * bs)
return x
class SpaceToChannel(nn.Module):
def __init__(self, downscale_factor=2):
super().__init__()
self.bs = downscale_factor
def forward(self, x):
N, C, H, W = x.size()
x = x.view(N, C, H // self.bs, self.bs, W // self.bs, self.bs) # (N, C, H//bs, bs, W//bs, bs)
x = x.permute(0, 3, 5, 1, 2, 4).contiguous() # (N, bs, bs, C, H//bs, W//bs)
x = x.view(N, C * (self.bs ** 2), H // self.bs, W // self.bs) # (N, C*bs^2, H//bs, W//bs)
return x
class Conv2dSame(nn.Conv2d):
""" Tensorflow like 'SAME' convolution wrapper for 2D convolutions
"""
def __init__(self, in_channels, out_channels, kernel_size, stride=1,
padding=0, dilation=1, groups=1, bias=True):
super(Conv2dSame, self).__init__(
in_channels, out_channels, kernel_size, stride, 0, dilation,
groups, bias)
def forward(self, x):
ih, iw = x.size()[-2:]
kh, kw = self.weight.size()[-2:]
pad_h = _calc_same_pad(ih, kh, self.stride[0], self.dilation[0])
pad_w = _calc_same_pad(iw, kw, self.stride[1], self.dilation[1])
if pad_h > 0 or pad_w > 0:
x = F.pad(x, [pad_w//2, pad_w - pad_w//2, pad_h//2, pad_h - pad_h//2])
return F.conv2d(x, self.weight, self.bias, self.stride,
self.padding, self.dilation, self.groups)
def conv2d_pad(in_chs, out_chs, kernel_size, **kwargs):
padding = kwargs.pop('padding', '')
kwargs.setdefault('bias', False)
if isinstance(padding, str):
# for any string padding, the padding will be calculated for you, one of three ways
padding = padding.lower()
if padding == 'same':
# TF compatible 'SAME' padding, has a performance and GPU memory allocation impact
if _is_static_pad(kernel_size, **kwargs):
# static case, no extra overhead
padding = _get_padding(kernel_size, **kwargs)
return nn.Conv2d(in_chs, out_chs, kernel_size, padding=padding, **kwargs)
else:
# dynamic padding
return Conv2dSame(in_chs, out_chs, kernel_size, **kwargs)
elif padding == 'valid':
# 'VALID' padding, same as padding=0
return nn.Conv2d(in_chs, out_chs, kernel_size, padding=0, **kwargs)
else:
# Default to PyTorch style 'same'-ish symmetric padding
padding = _get_padding(kernel_size, **kwargs)
return nn.Conv2d(in_chs, out_chs, kernel_size, padding=padding, **kwargs)
else:
# padding was specified as a number or pair
return nn.Conv2d(in_chs, out_chs, kernel_size, padding=padding, **kwargs)
class MuxConv(nn.Module):
""" MuxConv
"""
def __init__(self, in_channels, out_channels,
kernel_size=3, stride=1, padding='', scale_size=0, groups=1, depthwise=False, **kwargs):
super(MuxConv, self).__init__()
scale_size = scale_size if isinstance(scale_size, list) else [scale_size]
assert len(set(scale_size)) > 1, "use regular convolution for faster inference"
num_groups = len(scale_size)
kernel_size = kernel_size if isinstance(kernel_size, list) else [kernel_size] * num_groups
groups = groups if isinstance(groups, list) else [groups] * num_groups
in_splits = _split_channels(in_channels, num_groups)
out_splits = _split_channels(out_channels, num_groups)
convs = []
for k, in_ch, out_ch, scale, _group in zip(kernel_size, in_splits, out_splits, scale_size, groups):
# padding = (k - 1) // 2
if scale < 0: # space-to-channel -> learn -> channel-to-space
# if depthwise:
_group = in_ch * 4
convs.append(
nn.Sequential(
SpaceToChannel(2),
conv2d_pad(
in_ch * 4, out_ch * 4, k, stride=stride,
padding=padding, dilation=1, groups=_group, **kwargs),
ChannelToSpace(2),
)
)
elif scale > 0: # channel-to-space -> learn -> space-to-channel
# if depthwise:
_group = in_ch // 4
convs.append(
nn.Sequential(
ChannelToSpace(2),
conv2d_pad(
in_ch // 4, out_ch // 4, k, stride=stride,
padding=padding, dilation=1, groups=_group, **kwargs),
SpaceToChannel(2),
)
)
else:
# if depthwise:
_group = out_ch
convs.append(
conv2d_pad(
in_ch, out_ch, k, stride=stride,
padding=padding, dilation=1, groups=_group, **kwargs))
self.convs = nn.ModuleList(convs)
self.splits = in_splits
self.scale_size = scale_size
def forward(self, x):
x_split = torch.split(x, self.splits, 1)
x_out = []
for spx, conv in zip(x_split, self.convs):
x_out.append(conv(spx))
x = torch.cat(x_out, 1)
return x
class MixedConv2d(nn.Module):
""" Mixed Grouped Convolution
Based on MDConv and GroupedConv in MixNet impl:
https://github.com/tensorflow/tpu/blob/master/models/official/mnasnet/mixnet/custom_layers.py
"""
def __init__(self, in_channels, out_channels, kernel_size=3,
stride=1, padding='', dilated=False, depthwise=False, **kwargs):
super(MixedConv2d, self).__init__()
kernel_size = kernel_size if isinstance(kernel_size, list) else [kernel_size]
num_groups = len(kernel_size)
in_splits = _split_channels(in_channels, num_groups)
out_splits = _split_channels(out_channels, num_groups)
if depthwise:
conv_groups = out_splits
else:
groups = kwargs.pop('groups', 1)
if groups > 1:
conv_groups = _split_channels(groups, num_groups)
else:
conv_groups = [1] * num_groups
for idx, (k, in_ch, out_ch) in enumerate(zip(kernel_size, in_splits, out_splits)):
d = 1
# FIXME make compat with non-square kernel/dilations/strides
if stride == 1 and dilated:
d, k = (k - 1) // 2, 3
# conv_groups = out_ch if depthwise else kwargs.pop('groups', 1)
# use add_module to keep key space clean
self.add_module(
str(idx),
conv2d_pad(
in_ch, out_ch, k, stride=stride,
padding=padding, dilation=d, groups=conv_groups[idx], **kwargs)
)
self.splits = in_splits
def forward(self, x):
x_split = torch.split(x, self.splits, 1)
x_out = [c(x) for x, c in zip(x_split, self._modules.values())]
x = torch.cat(x_out, 1)
return x
# helper method
def select_conv2d(in_chs, out_chs, kernel_size, **kwargs):
scale_size = kwargs.pop('scales', 0)
if isinstance(kernel_size, list) or isinstance(scale_size, list):
# assert 'groups' not in kwargs # only use 'depthwise' bool arg
# We're going to use only lists for defining the MixedConv2d kernel groups,
# ints, tuples, other iterables will continue to pass to normal conv and specify h, w.
if isinstance(scale_size, list):
return MuxConv(in_chs, out_chs, kernel_size, scale_size=scale_size, **kwargs)
else:
return MixedConv2d(in_chs, out_chs, kernel_size, **kwargs)
else:
depthwise = kwargs.pop('depthwise', False)
groups = out_chs if depthwise else kwargs.pop('groups', 1)
return conv2d_pad(in_chs, out_chs, kernel_size, groups=groups, **kwargs)