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

#include "pad.cuh"

static __global__ void pad_f32(const float * x, float * dst, const int ne0, const int ne00, const int ne01, const int ne02, const int ne03) {
    // blockIdx.z: idx of ne2*ne3, aka ne02*ne03
    // blockIdx.y: idx of ne1
    // blockIDx.x: idx of ne0 / BLOCK_SIZE
    int nidx = threadIdx.x + blockIdx.x * blockDim.x;
    if (nidx >= ne0) {
        return;
    }

    // operation
    int offset_dst =
        nidx +
        blockIdx.y * ne0 +
        blockIdx.z * ne0 * gridDim.y;
    if (nidx < ne00 && blockIdx.y < (unsigned)ne01 && blockIdx.z < (unsigned)(ne02*ne03)) {
        int offset_src =
            nidx +
            blockIdx.y * ne00 +
            blockIdx.z * ne00 * ne01;
        dst[offset_dst] = x[offset_src];
    } else {
        dst[offset_dst] = 0.0f;
    }
}

static void pad_f32_cuda(const float * x, float * dst,
    const int ne00, const int ne01, const int ne02, const int ne03,
    const int ne0, const int ne1, const int ne2, const int ne3, cudaStream_t stream) {
    int num_blocks = (ne0 + CUDA_PAD_BLOCK_SIZE - 1) / CUDA_PAD_BLOCK_SIZE;
    dim3 gridDim(num_blocks, ne1, ne2*ne3);
    pad_f32<<<gridDim, CUDA_PAD_BLOCK_SIZE, 0, stream>>>(x, dst, ne0, ne00, ne01, ne02, ne03);
}

void ggml_cuda_op_pad(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(src0->ne[3] == 1 && dst->ne[3] == 1); // just 3D tensors

    pad_f32_cuda(src0_d, dst_d,
        src0->ne[0], src0->ne[1], src0->ne[2], src0->ne[3],
        dst->ne[0], dst->ne[1], dst->ne[2], dst->ne[3], stream);
}