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/*
Copyright (C) 2022-present Naver Corporation. All rights reserved.
Licensed under CC BY-NC-SA 4.0 (non-commercial use only).
*/
#include <torch/extension.h>
#include <cuda.h>
#include <cuda_runtime.h>
#include <vector>
#define CHECK_CUDA(tensor) {\
TORCH_CHECK((tensor).is_cuda(), #tensor " is not in cuda memory"); \
TORCH_CHECK((tensor).is_contiguous(), #tensor " is not contiguous"); }
void CHECK_KERNEL() {auto error = cudaGetLastError(); TORCH_CHECK( error == cudaSuccess, cudaGetErrorString(error));}
template < typename scalar_t >
__global__ void rope_2d_cuda_kernel(
//scalar_t* __restrict__ tokens,
torch::PackedTensorAccessor32<scalar_t,4,torch::RestrictPtrTraits> tokens,
const int64_t* __restrict__ pos,
const float base,
const float fwd )
// const int N, const int H, const int D )
{
// tokens shape = (B, N, H, D)
const int N = tokens.size(1);
const int H = tokens.size(2);
const int D = tokens.size(3);
// each block update a single token, for all heads
// each thread takes care of a single output
extern __shared__ float shared[];
float* shared_inv_freq = shared + D;
const int b = blockIdx.x / N;
const int n = blockIdx.x % N;
const int Q = D / 4;
// one token = [0..Q : Q..2Q : 2Q..3Q : 3Q..D]
// u_Y v_Y u_X v_X
// shared memory: first, compute inv_freq
if (threadIdx.x < Q)
shared_inv_freq[threadIdx.x] = fwd / powf(base, threadIdx.x/float(Q));
__syncthreads();
// start of X or Y part
const int X = threadIdx.x < D/2 ? 0 : 1;
const int m = (X*D/2) + (threadIdx.x % Q); // index of u_Y or u_X
// grab the cos,sin appropriate for me
const float freq = pos[blockIdx.x*2+X] * shared_inv_freq[threadIdx.x % Q];
const float cos = cosf(freq);
const float sin = sinf(freq);
/*
float* shared_cos_sin = shared + D + D/4;
if ((threadIdx.x % (D/2)) < Q)
shared_cos_sin[m+0] = cosf(freq);
else
shared_cos_sin[m+Q] = sinf(freq);
__syncthreads();
const float cos = shared_cos_sin[m+0];
const float sin = shared_cos_sin[m+Q];
*/
for (int h = 0; h < H; h++)
{
// then, load all the token for this head in shared memory
shared[threadIdx.x] = tokens[b][n][h][threadIdx.x];
__syncthreads();
const float u = shared[m];
const float v = shared[m+Q];
// write output
if ((threadIdx.x % (D/2)) < Q)
tokens[b][n][h][threadIdx.x] = u*cos - v*sin;
else
tokens[b][n][h][threadIdx.x] = v*cos + u*sin;
}
}
void rope_2d_cuda( torch::Tensor tokens, const torch::Tensor pos, const float base, const float fwd )
{
const int B = tokens.size(0); // batch size
const int N = tokens.size(1); // sequence length
const int H = tokens.size(2); // number of heads
const int D = tokens.size(3); // dimension per head
TORCH_CHECK(tokens.stride(3) == 1 && tokens.stride(2) == D, "tokens are not contiguous");
TORCH_CHECK(pos.is_contiguous(), "positions are not contiguous");
TORCH_CHECK(pos.size(0) == B && pos.size(1) == N && pos.size(2) == 2, "bad pos.shape");
TORCH_CHECK(D % 4 == 0, "token dim must be multiple of 4");
// one block for each layer, one thread per local-max
const int THREADS_PER_BLOCK = D;
const int N_BLOCKS = B * N; // each block takes care of H*D values
const int SHARED_MEM = sizeof(float) * (D + D/4);
AT_DISPATCH_FLOATING_TYPES_AND_HALF(tokens.type(), "rope_2d_cuda", ([&] {
rope_2d_cuda_kernel<scalar_t> <<<N_BLOCKS, THREADS_PER_BLOCK, SHARED_MEM>>> (
//tokens.data_ptr<scalar_t>(),
tokens.packed_accessor32<scalar_t,4,torch::RestrictPtrTraits>(),
pos.data_ptr<int64_t>(),
base, fwd); //, N, H, D );
}));
}
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