code/src/models/layers/msdcn.py

import torch
import torch.nn as nn
import math

from torch.nn.init import zeros_
from typing import Any
from torch.autograd import Function
from torch.cuda.amp.autocast_mode import custom_bwd, custom_fwd

import triton
import triton.language as tl

@triton.autotune(
    configs=[
        triton.Config({'BLOCK_SIZE': 64,}, num_stages=1, num_warps=2),
        # triton.Config({'BLOCK_SIZE': 64, }, num_stages=1, num_warps=1),
    ],
    key=['B', 'H', 'W', 'G', 'C', 'K'],
)
@triton.jit
def forward_kernel(
        B: tl.constexpr,
        H: tl.constexpr, # image_size_h
        W: tl.constexpr, # image_size_w
        G: tl.constexpr, # num_channels_per_group
        C: tl.constexpr, # num_groups
        K: tl.constexpr, # kernel size
        input_ptr,   # input features [B, H, W, G, C]
        deformable_ptr, # deformable offsets [B, H, W, G, 2*K + K]
        weights_ptr, # weights [B, H, W, G, K]
        out_ptr, # out [B, H, W, G, C]
        BLOCK_SIZE: tl.constexpr, # a micro block to process in the Group
):
    pid = tl.program_id(0)
    wid = pid % W
    hid = pid // W % H
    gid = pid // (W * H) % G
    bid = pid // (W * H * G)

    id_mask = (hid < H) & (wid < W) & (gid < G) & (bid < B)
    common_offset = bid*H*W*G + hid*W*G + wid*G + gid
    batch_base = bid * H * W * G * C

    for block_base in tl.static_range(0, C, BLOCK_SIZE):
        buffer = tl.zeros((BLOCK_SIZE, ), dtype=tl.float32)
        block_offset = tl.arange(0, BLOCK_SIZE) + block_base
        block_mask = (block_offset < C) & id_mask
        for k in tl.static_range(K):
            deformable_offset = (common_offset * K + k) * 2

            x = tl.load(deformable_ptr + deformable_offset, mask=id_mask, other=0.0) + wid
            y = tl.load(deformable_ptr + deformable_offset + 1, mask=id_mask, other=0.0) + hid

            floor_x = x.to(tl.int32)
            floor_y = y.to(tl.int32)
            ceil_x = floor_x + 1
            ceil_y = floor_y + 1

            # load top left
            tl_weight = (ceil_x - x) * (ceil_y - y)
            tl_block_offset = (batch_base + floor_y * W * G * C + floor_x * G * C + gid * C) #+ k * BLOCK_SIZE
            tl_block_mask = (floor_y >= 0) & (floor_x >= 0) & (floor_x < W) & (floor_y < H)

            # load top right
            tr_weight = (x - floor_x) * (ceil_y - y)
            tr_block_offset = (batch_base + floor_y * W * G * C + ceil_x * G * C + gid * C) #+ k * BLOCK_SIZE
            tr_block_mask = (floor_y >= 0) & (ceil_x < W) & (floor_y < H) & (ceil_x >= 0)
            # load bottom left
            bl_weight = (ceil_x - x) * (y - floor_y)
            bl_block_offset = (batch_base + ceil_y * W * G * C + floor_x * G * C + gid * C) #+ k * BLOCK_SIZE
            bl_block_mask = (ceil_y < H) & (ceil_y >= 0) & (floor_x < W) & (floor_x >= 0)
            # load bottom right
            br_weight = (x - floor_x) * (y - floor_y)
            br_block_offset = (batch_base + ceil_y * W * G * C + ceil_x * G * C + gid * C) #+ k * BLOCK_SIZE
            br_block_mask = (ceil_y < H) & (ceil_y >= 0) & (ceil_x < W) & (ceil_x >= 0)

            # load dynamic weight and mask
            weights_offset = common_offset*K + k
            weight = tl.load(weights_ptr + weights_offset, mask=id_mask, other=0.0)



            tl_block_input = tl.load(input_ptr + tl_block_offset + block_offset, mask=tl_block_mask & block_mask, other=0.0)
            tl_block_input = tl_block_input * tl_weight

            # load top right
            tr_block_input = tl.load(input_ptr + tr_block_offset + block_offset, mask=tr_block_mask & block_mask, other=0.0)
            tr_block_input = tr_block_input * tr_weight
            # load bottom left
            bl_block_input = tl.load(input_ptr + bl_block_offset + block_offset, mask=bl_block_mask & block_mask, other=0.0)
            bl_block_input = bl_block_input * bl_weight
            # load bottom right
            br_block_input = tl.load(input_ptr + br_block_offset + block_offset, mask=br_block_mask & block_mask, other=0.0)
            br_block_input = br_block_input * br_weight

            # sampled
            sampled_input = tl_block_input + tr_block_input + bl_block_input + br_block_input

            weighted_sampled_input = sampled_input * weight
            buffer = buffer + weighted_sampled_input
        # store to out_ptr
        tl.store(out_ptr + common_offset*C + block_offset, buffer, mask=block_mask)

@triton.autotune(
    configs=[
        triton.Config({'BLOCK_SIZE': 64,}, num_stages=1, num_warps=1),
        triton.Config({'BLOCK_SIZE': 64,}, num_stages=1, num_warps=2),
    ],
    key=['B', 'H', 'W', 'G', 'C', 'K'],
)
@triton.jit
def backward_kernel(
        B: tl.constexpr,
        H: tl.constexpr, # image_size_h
        W: tl.constexpr, # image_size_w
        G: tl.constexpr, # num_groups
        C: tl.constexpr, # num_channels_per_group
        K: tl.constexpr, # kernel size
        input_ptr,   # input features [B, H, W, G, C]
        deformable_ptr, # deformable offsets [B, H, W, G, K, 2]
        weights_ptr, # weights [B, H, W, G, K]
        grad_ptr, # out [B, H, W, G, C]
        grad_input_ptr,   # input features [B, H, W, G, C]
        grad_deformable_ptr, # deformable offsets [B, H, W, G, K, 2]
        grad_weights_ptr, # weights [B, H, W, G, K]
        BLOCK_SIZE: tl.constexpr, # a micro block to process in the Group
):

    pid = tl.program_id(0)
    wid = pid % W
    hid = pid // W % H
    gid = pid // (W * H) % G
    bid = pid // (W * H * G)

    id_mask = (hid < H) & (wid < W) & (gid < G) & (bid < B)

    common_offset = bid*H*W*G + hid*W*G + wid*G + gid
    batch_base = bid * H * W * G * C
    for k in tl.static_range(K):
        # load dynamic weight and mask
        weights_offset = common_offset*K + k
        weight = tl.load(weights_ptr + weights_offset, mask=id_mask, other=0.0)
        dodx = tl.zeros((1,), dtype=grad_deformable_ptr.type.element_ty)
        dody = tl.zeros((1,), dtype=grad_deformable_ptr.type.element_ty)
        dodw = tl.zeros((1,), dtype=grad_weights_ptr.type.element_ty)
        deformable_offset = (common_offset * K + k)*2
        x = tl.load(deformable_ptr + deformable_offset, mask=id_mask, other=0.0) + wid
        y = tl.load(deformable_ptr + deformable_offset + 1, mask=id_mask, other=0.0) + hid
        for block_base in tl.static_range(0, C, BLOCK_SIZE):
            block_offset = tl.arange(0, BLOCK_SIZE) + block_base
            block_mask = (block_offset < C) & id_mask
            grad = tl.load(grad_ptr+common_offset*C + block_offset, mask=block_mask, other=0.0)
            dods = weight*grad

            floor_x = x.to(tl.int32)
            floor_y = y.to(tl.int32)
            ceil_x = floor_x + 1
            ceil_y = floor_y + 1

            # load top left
            tl_weight = (ceil_x - x) * (ceil_y - y)
            tl_block_offset = (batch_base + floor_y * W * G * C + floor_x * G * C + gid * C) + block_offset
            tl_block_mask = ((floor_y >= 0) & (floor_x >= 0) & (floor_x < W) & (floor_y < H))
            tl_block_input = tl.load(input_ptr + tl_block_offset, mask=tl_block_mask & block_mask, other=0.0)
            tl_block_input_dot_grad = tl.sum(tl_block_input*grad, axis=0)
            dodx = dodx + -1 * tl_block_input_dot_grad * (ceil_y - y)
            dody = dody + -1 * tl_block_input_dot_grad * (ceil_x - x)
            dodw = dodw + tl_block_input_dot_grad * tl_weight

            dodtl = dods * tl_weight
            tl.atomic_add(grad_input_ptr + tl_block_offset, mask=tl_block_mask & block_mask, val=dodtl)


            # load top right
            tr_weight = (x - floor_x) * (ceil_y - y)
            tr_block_offset = (batch_base + floor_y * W * G * C + ceil_x * G * C + gid * C) + block_offset
            tr_block_mask = ((floor_y >= 0) & (ceil_x < W) & (floor_y < H) & (ceil_x >= 0))
            tr_block_input = tl.load(input_ptr + tr_block_offset, mask=tr_block_mask & block_mask, other=0.0)
            tr_block_input_dot_grad = tl.sum(tr_block_input*grad, axis=0)
            dodx = dodx + 1 * tr_block_input_dot_grad * (ceil_y - y)
            dody = dody + -1 * tr_block_input_dot_grad * (x - floor_x)
            dodw = dodw + tr_block_input_dot_grad*tr_weight

            dodtr = dods * tr_weight
            tl.atomic_add(grad_input_ptr + tr_block_offset, mask=tr_block_mask & block_mask, val=dodtr)


            # load bottom left
            bl_weight = (ceil_x - x) * (y - floor_y)
            bl_block_offset = (batch_base + ceil_y * W * G * C + floor_x * G * C + gid * C) + block_offset
            bl_block_mask = ((ceil_y < H) & (ceil_y >= 0) & (floor_x < W) & (floor_x >= 0))
            bl_block_input = tl.load(input_ptr + bl_block_offset, mask=bl_block_mask & block_mask, other=0.0)
            bl_block_input_dot_grad = tl.sum(bl_block_input*grad, axis=0)
            dodx = dodx + -1 * bl_block_input_dot_grad * (y - floor_y)
            dody = dody + 1 * bl_block_input_dot_grad * (ceil_x - x)
            dodw = dodw + bl_block_input_dot_grad*bl_weight

            dodbl = dods * bl_weight
            tl.atomic_add(grad_input_ptr + bl_block_offset, mask=bl_block_mask & block_mask, val=dodbl)


            # load bottom right
            br_weight = (x - floor_x) * (y - floor_y)
            br_block_offset = (batch_base + ceil_y * W * G * C + ceil_x * G * C + gid * C) + block_offset
            br_block_mask = ((ceil_y < H) & (ceil_y >= 0) & (ceil_x < W) & (ceil_x >= 0))
            br_block_input = tl.load(input_ptr + br_block_offset, mask=br_block_mask & block_mask, other=0.0)
            br_block_input_dot_grad = tl.sum(br_block_input*grad, axis=0)*br_block_mask

            dodx = dodx + 1 * br_block_input_dot_grad * (y - floor_y)
            dody = dody + 1 * br_block_input_dot_grad * (x - floor_x)
            dodw = dodw + br_block_input_dot_grad*br_weight

            dodbr = dods * br_weight
            tl.atomic_add(grad_input_ptr + br_block_offset, mask=br_block_mask  & block_mask, val=dodbr)
        dodx = dodx * weight
        dody = dody * weight
        tl.store(grad_weights_ptr + weights_offset + tl.arange(0, 1), dodw, mask=id_mask)
        tl.store(grad_deformable_ptr + deformable_offset + tl.arange(0, 1), dodx, mask=id_mask)
        tl.store(grad_deformable_ptr + deformable_offset + 1 + tl.arange(0, 1), dody, mask=id_mask)


class DCNFunction(Function):
    @staticmethod
    @custom_fwd
    def forward(ctx: Any, inputs, deformables, weights) -> Any:
        B, H, W, G, C = inputs.shape
        _, _, _, _, K, _ = deformables.shape
        out = torch.zeros_like(inputs)
        grid = lambda META: (B * H * W * G,)
        forward_kernel[grid](B, H, W, G, C, K, inputs, deformables, weights, out)
        ctx.save_for_backward(inputs, deformables, weights)
        return out

    @staticmethod
    @custom_bwd
    def backward(ctx: Any, *grad_outputs: Any) -> Any:
        grad_output = grad_outputs[0].contiguous()
        inputs, deformables, weights = ctx.saved_tensors
        B, H, W, G, C = inputs.shape
        _, _, _, _, K, _ = deformables.shape
        grad_inputs = torch.zeros_like(inputs)
        grad_deformables = torch.zeros_like(deformables)
        grad_weights = torch.zeros_like(weights)
        grid = lambda META: (B * H * W * G,)
        backward_kernel[grid](
            B, H, W, G, C, K,
            inputs,
            deformables,
            weights,
            grad_output,
            grad_inputs,
            grad_deformables,
            grad_weights,
        )
        return (grad_inputs, grad_deformables, grad_weights)


class MultiScaleDCN(nn.Module):
    def __init__(self, in_channels, groups, channels, kernels, deformable_biass=True):
        super().__init__()
        self.in_channels = in_channels
        self.groups = groups
        self.channels = channels
        self.kernels = kernels
        self.v = nn.Linear(in_channels, groups * channels, bias=True)
        self.qk_deformables = nn.Linear(in_channels, groups * kernels * 2, bias=True)
        self.qk_scales = nn.Linear(in_channels, groups * kernels, bias=False)
        self.qk_weights = nn.Linear(in_channels, groups*kernels, bias=True)
        self.out = nn.Linear(groups * channels, in_channels)
        self.deformables_prior = nn.Parameter(torch.randn((1, 1, 1, 1, kernels, 2)), requires_grad=False)
        self.deformables_scale = nn.Parameter(torch.ones((1, 1, 1, groups, 1, 1)), requires_grad=True)
        self.max_scale = 6
        self._init_weights()
    def _init_weights(self):
        zeros_(self.qk_deformables.weight.data)
        zeros_(self.qk_scales.weight.data)
        zeros_(self.qk_deformables.bias.data)
        zeros_(self.qk_weights.weight.data)
        zeros_(self.v.bias.data)
        zeros_(self.out.bias.data)
        num_prior = int(self.kernels ** 0.5)
        dx = torch.linspace(-1, 1, num_prior, device="cuda")
        dy = torch.linspace(-1, 1, num_prior, device="cuda")
        dxy = torch.meshgrid([dx, dy], indexing="xy")
        dxy = torch.stack(dxy, dim=-1)
        dxy = dxy.view(-1, 2)
        self.deformables_prior.data[..., :num_prior*num_prior, :] = dxy
        for i in range(self.groups):
           scale = (i+1)/self.groups - 0.0001
           inv_scale = math.log((scale)/(1-scale))
           self.deformables_scale.data[..., i, :, :] = inv_scale
    def forward(self, x):
        B, H, W, _ = x.shape
        v = self.v(x).view(B, H, W, self.groups, self.channels)
        deformables = self.qk_deformables(x).view(B, H, W, self.groups, self.kernels, 2)
        scale = self.qk_scales(x).view(B, H, W, self.groups, self.kernels, 1) + self.deformables_scale
        deformables = (deformables + self.deformables_prior ) * scale.sigmoid()*self.max_scale
        weights = self.qk_weights(x).view(B, H, W, self.groups, self.kernels)
        out = DCNFunction.apply(v, deformables, weights)
        out = out.view(B, H, W, -1)
        out = self.out(out)
        return out