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#include <torch/extension.h>
#include <cuda.h>
#include <cuda_runtime.h>
#include <vector>
#define BLOCK_H 4
#define BLOCK_W 8
#define BLOCK_HW BLOCK_H * BLOCK_W
#define CHANNEL_STRIDE 32
__forceinline__ __device__
bool within_bounds(int h, int w, int H, int W) {
return h >= 0 && h < H && w >= 0 && w < W;
}
template <typename scalar_t>
__global__ void corr_forward_kernel(
const torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> fmap1,
const torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> fmap2,
const torch::PackedTensorAccessor32<scalar_t,5,torch::RestrictPtrTraits> coords,
torch::PackedTensorAccessor32<scalar_t,5,torch::RestrictPtrTraits> corr,
int r)
{
const int b = blockIdx.x;
const int h0 = blockIdx.y * blockDim.x;
const int w0 = blockIdx.z * blockDim.y;
const int tid = threadIdx.x * blockDim.y + threadIdx.y;
const int H1 = fmap1.size(1);
const int W1 = fmap1.size(2);
const int H2 = fmap2.size(1);
const int W2 = fmap2.size(2);
const int N = coords.size(1);
const int C = fmap1.size(3);
__shared__ scalar_t f1[CHANNEL_STRIDE][BLOCK_HW+1];
__shared__ scalar_t f2[CHANNEL_STRIDE][BLOCK_HW+1];
__shared__ scalar_t x2s[BLOCK_HW];
__shared__ scalar_t y2s[BLOCK_HW];
for (int c=0; c<C; c+=CHANNEL_STRIDE) {
for (int k=0; k<BLOCK_HW; k+=BLOCK_HW/CHANNEL_STRIDE) {
int k1 = k + tid / CHANNEL_STRIDE;
int h1 = h0 + k1 / BLOCK_W;
int w1 = w0 + k1 % BLOCK_W;
int c1 = tid % CHANNEL_STRIDE;
auto fptr = fmap1[b][h1][w1];
if (within_bounds(h1, w1, H1, W1))
f1[c1][k1] = fptr[c+c1];
else
f1[c1][k1] = 0.0;
}
__syncthreads();
for (int n=0; n<N; n++) {
int h1 = h0 + threadIdx.x;
int w1 = w0 + threadIdx.y;
if (within_bounds(h1, w1, H1, W1)) {
x2s[tid] = coords[b][n][h1][w1][0];
y2s[tid] = coords[b][n][h1][w1][1];
}
scalar_t dx = x2s[tid] - floor(x2s[tid]);
scalar_t dy = y2s[tid] - floor(y2s[tid]);
int rd = 2*r + 1;
for (int iy=0; iy<rd+1; iy++) {
for (int ix=0; ix<rd+1; ix++) {
for (int k=0; k<BLOCK_HW; k+=BLOCK_HW/CHANNEL_STRIDE) {
int k1 = k + tid / CHANNEL_STRIDE;
int h2 = static_cast<int>(floor(y2s[k1]))-r+iy;
int w2 = static_cast<int>(floor(x2s[k1]))-r+ix;
int c2 = tid % CHANNEL_STRIDE;
auto fptr = fmap2[b][h2][w2];
if (within_bounds(h2, w2, H2, W2))
f2[c2][k1] = fptr[c+c2];
else
f2[c2][k1] = 0.0;
}
__syncthreads();
scalar_t s = 0.0;
for (int k=0; k<CHANNEL_STRIDE; k++)
s += f1[k][tid] * f2[k][tid];
int ix_nw = H1*W1*((iy-1) + rd*(ix-1));
int ix_ne = H1*W1*((iy-1) + rd*ix);
int ix_sw = H1*W1*(iy + rd*(ix-1));
int ix_se = H1*W1*(iy + rd*ix);
scalar_t nw = s * (dy) * (dx);
scalar_t ne = s * (dy) * (1-dx);
scalar_t sw = s * (1-dy) * (dx);
scalar_t se = s * (1-dy) * (1-dx);
scalar_t* corr_ptr = &corr[b][n][0][h1][w1];
if (iy > 0 && ix > 0 && within_bounds(h1, w1, H1, W1))
*(corr_ptr + ix_nw) += nw;
if (iy > 0 && ix < rd && within_bounds(h1, w1, H1, W1))
*(corr_ptr + ix_ne) += ne;
if (iy < rd && ix > 0 && within_bounds(h1, w1, H1, W1))
*(corr_ptr + ix_sw) += sw;
if (iy < rd && ix < rd && within_bounds(h1, w1, H1, W1))
*(corr_ptr + ix_se) += se;
}
}
}
}
}
template <typename scalar_t>
__global__ void corr_backward_kernel(
const torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> fmap1,
const torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> fmap2,
const torch::PackedTensorAccessor32<scalar_t,5,torch::RestrictPtrTraits> coords,
const torch::PackedTensorAccessor32<scalar_t,5,torch::RestrictPtrTraits> corr_grad,
torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> fmap1_grad,
torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> fmap2_grad,
torch::PackedTensorAccessor32<scalar_t,5,torch::RestrictPtrTraits> coords_grad,
int r)
{
const int b = blockIdx.x;
const int h0 = blockIdx.y * blockDim.x;
const int w0 = blockIdx.z * blockDim.y;
const int tid = threadIdx.x * blockDim.y + threadIdx.y;
const int H1 = fmap1.size(1);
const int W1 = fmap1.size(2);
const int H2 = fmap2.size(1);
const int W2 = fmap2.size(2);
const int N = coords.size(1);
const int C = fmap1.size(3);
__shared__ scalar_t f1[CHANNEL_STRIDE][BLOCK_HW+1];
__shared__ scalar_t f2[CHANNEL_STRIDE][BLOCK_HW+1];
__shared__ scalar_t f1_grad[CHANNEL_STRIDE][BLOCK_HW+1];
__shared__ scalar_t f2_grad[CHANNEL_STRIDE][BLOCK_HW+1];
__shared__ scalar_t x2s[BLOCK_HW];
__shared__ scalar_t y2s[BLOCK_HW];
for (int c=0; c<C; c+=CHANNEL_STRIDE) {
for (int k=0; k<BLOCK_HW; k+=BLOCK_HW/CHANNEL_STRIDE) {
int k1 = k + tid / CHANNEL_STRIDE;
int h1 = h0 + k1 / BLOCK_W;
int w1 = w0 + k1 % BLOCK_W;
int c1 = tid % CHANNEL_STRIDE;
auto fptr = fmap1[b][h1][w1];
if (within_bounds(h1, w1, H1, W1))
f1[c1][k1] = fptr[c+c1];
else
f1[c1][k1] = 0.0;
f1_grad[c1][k1] = 0.0;
}
__syncthreads();
int h1 = h0 + threadIdx.x;
int w1 = w0 + threadIdx.y;
for (int n=0; n<N; n++) {
x2s[tid] = coords[b][n][h1][w1][0];
y2s[tid] = coords[b][n][h1][w1][1];
scalar_t dx = x2s[tid] - floor(x2s[tid]);
scalar_t dy = y2s[tid] - floor(y2s[tid]);
int rd = 2*r + 1;
for (int iy=0; iy<rd+1; iy++) {
for (int ix=0; ix<rd+1; ix++) {
for (int k=0; k<BLOCK_HW; k+=BLOCK_HW/CHANNEL_STRIDE) {
int k1 = k + tid / CHANNEL_STRIDE;
int h2 = static_cast<int>(floor(y2s[k1]))-r+iy;
int w2 = static_cast<int>(floor(x2s[k1]))-r+ix;
int c2 = tid % CHANNEL_STRIDE;
auto fptr = fmap2[b][h2][w2];
if (within_bounds(h2, w2, H2, W2))
f2[c2][k1] = fptr[c+c2];
else
f2[c2][k1] = 0.0;
f2_grad[c2][k1] = 0.0;
}
__syncthreads();
const scalar_t* grad_ptr = &corr_grad[b][n][0][h1][w1];
scalar_t g = 0.0;
int ix_nw = H1*W1*((iy-1) + rd*(ix-1));
int ix_ne = H1*W1*((iy-1) + rd*ix);
int ix_sw = H1*W1*(iy + rd*(ix-1));
int ix_se = H1*W1*(iy + rd*ix);
if (iy > 0 && ix > 0 && within_bounds(h1, w1, H1, W1))
g += *(grad_ptr + ix_nw) * dy * dx;
if (iy > 0 && ix < rd && within_bounds(h1, w1, H1, W1))
g += *(grad_ptr + ix_ne) * dy * (1-dx);
if (iy < rd && ix > 0 && within_bounds(h1, w1, H1, W1))
g += *(grad_ptr + ix_sw) * (1-dy) * dx;
if (iy < rd && ix < rd && within_bounds(h1, w1, H1, W1))
g += *(grad_ptr + ix_se) * (1-dy) * (1-dx);
for (int k=0; k<CHANNEL_STRIDE; k++) {
f1_grad[k][tid] += g * f2[k][tid];
f2_grad[k][tid] += g * f1[k][tid];
}
for (int k=0; k<BLOCK_HW; k+=BLOCK_HW/CHANNEL_STRIDE) {
int k1 = k + tid / CHANNEL_STRIDE;
int h2 = static_cast<int>(floor(y2s[k1]))-r+iy;
int w2 = static_cast<int>(floor(x2s[k1]))-r+ix;
int c2 = tid % CHANNEL_STRIDE;
scalar_t* fptr = &fmap2_grad[b][h2][w2][0];
if (within_bounds(h2, w2, H2, W2))
atomicAdd(fptr+c+c2, f2_grad[c2][k1]);
}
}
}
}
__syncthreads();
for (int k=0; k<BLOCK_HW; k+=BLOCK_HW/CHANNEL_STRIDE) {
int k1 = k + tid / CHANNEL_STRIDE;
int h1 = h0 + k1 / BLOCK_W;
int w1 = w0 + k1 % BLOCK_W;
int c1 = tid % CHANNEL_STRIDE;
scalar_t* fptr = &fmap1_grad[b][h1][w1][0];
if (within_bounds(h1, w1, H1, W1))
fptr[c+c1] += f1_grad[c1][k1];
}
}
}
std::vector<torch::Tensor> corr_cuda_forward(
torch::Tensor fmap1,
torch::Tensor fmap2,
torch::Tensor coords,
int radius)
{
const auto B = coords.size(0);
const auto N = coords.size(1);
const auto H = coords.size(2);
const auto W = coords.size(3);
const auto rd = 2 * radius + 1;
auto opts = fmap1.options();
auto corr = torch::zeros({B, N, rd*rd, H, W}, opts);
const dim3 blocks(B, (H+BLOCK_H-1)/BLOCK_H, (W+BLOCK_W-1)/BLOCK_W);
const dim3 threads(BLOCK_H, BLOCK_W);
corr_forward_kernel<float><<<blocks, threads>>>(
fmap1.packed_accessor32<float,4,torch::RestrictPtrTraits>(),
fmap2.packed_accessor32<float,4,torch::RestrictPtrTraits>(),
coords.packed_accessor32<float,5,torch::RestrictPtrTraits>(),
corr.packed_accessor32<float,5,torch::RestrictPtrTraits>(),
radius);
return {corr};
}
std::vector<torch::Tensor> corr_cuda_backward(
torch::Tensor fmap1,
torch::Tensor fmap2,
torch::Tensor coords,
torch::Tensor corr_grad,
int radius)
{
const auto B = coords.size(0);
const auto N = coords.size(1);
const auto H1 = fmap1.size(1);
const auto W1 = fmap1.size(2);
const auto H2 = fmap2.size(1);
const auto W2 = fmap2.size(2);
const auto C = fmap1.size(3);
auto opts = fmap1.options();
auto fmap1_grad = torch::zeros({B, H1, W1, C}, opts);
auto fmap2_grad = torch::zeros({B, H2, W2, C}, opts);
auto coords_grad = torch::zeros({B, N, H1, W1, 2}, opts);
const dim3 blocks(B, (H1+BLOCK_H-1)/BLOCK_H, (W1+BLOCK_W-1)/BLOCK_W);
const dim3 threads(BLOCK_H, BLOCK_W);
corr_backward_kernel<float><<<blocks, threads>>>(
fmap1.packed_accessor32<float,4,torch::RestrictPtrTraits>(),
fmap2.packed_accessor32<float,4,torch::RestrictPtrTraits>(),
coords.packed_accessor32<float,5,torch::RestrictPtrTraits>(),
corr_grad.packed_accessor32<float,5,torch::RestrictPtrTraits>(),
fmap1_grad.packed_accessor32<float,4,torch::RestrictPtrTraits>(),
fmap2_grad.packed_accessor32<float,4,torch::RestrictPtrTraits>(),
coords_grad.packed_accessor32<float,5,torch::RestrictPtrTraits>(),
radius);
return {fmap1_grad, fmap2_grad, coords_grad};
} |