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""" Padding Helpers
Hacked together by / Copyright 2020 Ross Wightman
"""
import math
from typing import List, Tuple
import torch
import torch.nn.functional as F
# Calculate symmetric padding for a convolution
def get_padding(kernel_size: int, stride: int = 1, dilation: int = 1, **_) -> int:
padding = ((stride - 1) + dilation * (kernel_size - 1)) // 2
return padding
# Calculate asymmetric TensorFlow-like 'SAME' padding for a convolution
def get_same_padding(x: int, kernel_size: int, stride: int, dilation: int):
if isinstance(x, torch.Tensor):
return torch.clamp(((x / stride).ceil() - 1) * stride + (kernel_size - 1) * dilation + 1 - x, min=0)
else:
return max((math.ceil(x / stride) - 1) * stride + (kernel_size - 1) * dilation + 1 - x, 0)
# Can SAME padding for given args be done statically?
def is_static_pad(kernel_size: int, stride: int = 1, dilation: int = 1, **_):
return stride == 1 and (dilation * (kernel_size - 1)) % 2 == 0
def pad_same_arg(
input_size: List[int],
kernel_size: List[int],
stride: List[int],
dilation: List[int] = (1, 1),
) -> List[int]:
ih, iw = input_size
kh, kw = kernel_size
pad_h = get_same_padding(ih, kh, stride[0], dilation[0])
pad_w = get_same_padding(iw, kw, stride[1], dilation[1])
return [pad_w // 2, pad_w - pad_w // 2, pad_h // 2, pad_h - pad_h // 2]
# Dynamically pad input x with 'SAME' padding for conv with specified args
def pad_same(
x,
kernel_size: List[int],
stride: List[int],
dilation: List[int] = (1, 1),
value: float = 0,
):
ih, iw = x.size()[-2:]
pad_h = get_same_padding(ih, kernel_size[0], stride[0], dilation[0])
pad_w = get_same_padding(iw, kernel_size[1], stride[1], dilation[1])
x = F.pad(x, (pad_w // 2, pad_w - pad_w // 2, pad_h // 2, pad_h - pad_h // 2), value=value)
return x
def get_padding_value(padding, kernel_size, **kwargs) -> Tuple[Tuple, bool]:
dynamic = 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)
else:
# dynamic 'SAME' padding, has runtime/GPU memory overhead
padding = 0
dynamic = True
elif padding == 'valid':
# 'VALID' padding, same as padding=0
padding = 0
else:
# Default to PyTorch style 'same'-ish symmetric padding
padding = get_padding(kernel_size, **kwargs)
return padding, dynamic
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