llama.cpp/ggml/src/ggml-cuda/sumrows.cu

#include "sumrows.cuh"

static __global__ void k_sum_rows_f32(const float * x, float * dst, const int ncols) {
    const int row = blockIdx.x;
    const int col = threadIdx.x;

    float sum = 0.0f;
    for (int i = col; i < ncols; i += blockDim.x) {
        sum += x[row * ncols + i];
    }

    sum = warp_reduce_sum(sum);

    if (col == 0) {
        dst[row] = sum;
    }
}

static void sum_rows_f32_cuda(const float * x, float * dst, const int ncols, const int nrows, cudaStream_t stream) {
    const dim3 block_dims(WARP_SIZE, 1, 1);
    const dim3 block_nums(nrows, 1, 1);
    k_sum_rows_f32<<<block_nums, block_dims, 0, stream>>>(x, dst, ncols);
}

void ggml_cuda_op_sum_rows(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);
    GGML_ASSERT(ggml_is_contiguous(src0));


    const int64_t ncols = src0->ne[0];
    const int64_t nrows = ggml_nrows(src0);

    sum_rows_f32_cuda(src0_d, dst_d, ncols, nrows, stream);
}