conv3d_same.py

""" Conv3d w/ Same Padding
modified from:
https://github.com/rwightman/pytorch-image-models/blob/a2727c1bf78ba0d7b5727f5f95e37fb7f8866b1f/timm/models/layers/conv2d_same.py
https://github.com/rwightman/pytorch-image-models/blob/a2727c1bf78ba0d7b5727f5f95e37fb7f8866b1f/timm/models/layers/padding.py
"""
import math
import torch
import torch.nn as nn
import torch.nn.functional as F
from typing import Tuple, Optional, List


# 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, k: int, s: int, d: int):
    return max((math.ceil(x / s) - 1) * s + (k - 1) * d + 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


# Dynamically pad input x with 'SAME' padding for conv with specified args
def pad_same(x, k: List[int], s: List[int], d: List[int] = (1, 1, 1), value: float = 0):
    ih, iw, iz = x.size()[-3:]
    pad_h = get_same_padding(ih, k[0], s[0], d[0])
    pad_w = get_same_padding(iw, k[1], s[1], d[1])
    pad_z = get_same_padding(iz, k[2], s[2], d[2])
    if pad_h > 0 or pad_w > 0 or pad_z > 0:
        x = F.pad(x, [pad_w // 2, pad_w - pad_w // 2, pad_h // 2, pad_h - pad_h // 2, pad_z // 2, pad_z - pad_z // 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


def conv3d_same(
        x, weight: torch.Tensor, bias: Optional[torch.Tensor] = None, stride: Tuple[int, int, int] = (1, 1, 1),
        padding: Tuple[int, int, int] = (0, 0, 0), dilation: Tuple[int, int, int] = (1, 1, 1), groups: int = 1):
    x = pad_same(x, weight.shape[-3:], stride, dilation)
    return F.conv3d(x, weight, bias, stride, (0, 0, 0), dilation, groups)


class Conv3dSame(nn.Conv3d):
    """ Tensorflow like 'SAME' convolution wrapper for 3d convolutions
    """

    def __init__(self, in_channels, out_channels, kernel_size, stride=1,
                 padding=0, dilation=1, groups=1, bias=True):
        super(Conv3dSame, self).__init__(
            in_channels, out_channels, kernel_size, stride, 0, dilation, groups, bias)

    def forward(self, x):
        return conv3d_same(x, self.weight, self.bias, self.stride, self.padding, self.dilation, self.groups)


def create_conv3d_pad(in_chs, out_chs, kernel_size, **kwargs):
    padding = kwargs.pop('padding', '')
    kwargs.setdefault('bias', False)
    padding, is_dynamic = get_padding_value(padding, kernel_size, **kwargs)
    if is_dynamic:
        return Conv3dSame(in_chs, out_chs, kernel_size, **kwargs)
    else:
        return nn.Conv3d(in_chs, out_chs, kernel_size, padding=padding, **kwargs)