1.  joinable()函数

int LocalOptimizationProcess::Stop()
{
    stop_thread_ = true;
    cond_.notify_all();
    
    LOGD("LocalOptimizationProcess Thread Join()");
    if (thread_->joinable())
    {
        thread_->join();
    }
    LOGD("LocalOptimizationProcess Thread Stoped");

    return 0;
}