llama.cpp/ggml-cuda/alibi.cu

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#include "alibi.cuh"
static __global__ void alibi_f32(const float * x, float * dst, const int ncols, const int k_rows,
const int n_heads_log2_floor, const float m0, const float m1) {
const int col = blockDim.x*blockIdx.x + threadIdx.x;
if (col >= ncols) {
return;
}
const int row = blockDim.y*blockIdx.y + threadIdx.y;
const int i = row*ncols + col;
const int k = row/k_rows;
float m_k;
if (k < n_heads_log2_floor) {
m_k = powf(m0, k + 1);
} else {
m_k = powf(m1, 2 * (k - n_heads_log2_floor) + 1);
}
dst[i] = col * m_k + x[i];
}
static void alibi_f32_cuda(const float * x, float * dst, const int ncols, const int nrows,
const int k_rows, const int n_heads_log2_floor, const float m0,
const float m1, cudaStream_t stream) {
const dim3 block_dims(CUDA_ALIBI_BLOCK_SIZE, 1, 1);
const int num_blocks_x = (ncols + CUDA_ALIBI_BLOCK_SIZE - 1) / (CUDA_ALIBI_BLOCK_SIZE);
const dim3 block_nums(num_blocks_x, nrows, 1);
alibi_f32<<<block_nums, block_dims, 0, stream>>>(x, dst, ncols, k_rows, n_heads_log2_floor, m0, m1);
}
void ggml_cuda_op_alibi(ggml_backend_cuda_context & ctx, ggml_tensor * dst) {
const ggml_tensor * src0 = dst->src[0];
const float * src0_d = (const float *)src0->data;
float * dst_d = (float *)dst->data;
cudaStream_t stream = ctx.stream();
GGML_ASSERT(src0->type == GGML_TYPE_F32);
GGML_ASSERT( dst->type == GGML_TYPE_F32);
const int64_t ne00 = src0->ne[0];
const int64_t ne01 = src0->ne[1];
const int64_t ne02 = src0->ne[2];
const int64_t nrows = ggml_nrows(src0);
//const int n_past = ((int32_t *) dst->op_params)[0];
const int n_head = ((int32_t *) dst->op_params)[1];
float max_bias;
memcpy(&max_bias, (int32_t *) dst->op_params + 2, sizeof(float));
//GGML_ASSERT(ne01 + n_past == ne00);
GGML_ASSERT(n_head == ne02);
const int n_heads_log2_floor = 1 << (int) floor(log2(n_head));
const float m0 = powf(2.0f, -(max_bias) / n_heads_log2_floor);
const float m1 = powf(2.0f, -(max_bias / 2.0f) / n_heads_log2_floor);
alibi_f32_cuda(src0_d, dst_d, ne00, nrows, ne01, n_heads_log2_floor, m0, m1, stream);
}