Function ncclAllReduce 

pub unsafe extern "C" fn ncclAllReduce(
    sendbuf: *const c_void,
    recvbuf: *mut c_void,
    count: usize,
    datatype: NcclDataType,
    op: NcclRedOp,
    comm: NcclComm,
    stream: u64,
) -> NcclResult