Function faiss_GpuResources_getAsyncCopyStream 

pub unsafe extern "C" fn faiss_GpuResources_getAsyncCopyStream(
    arg1: *mut FaissGpuResources,
    arg2: c_int,
    arg3: *mut cudaStream_t,
) -> c_int

Returns the stream on which we perform async CPU <-> GPU copies