Created by: dzhwinter

maybe open an issue is the way to make us agree on some complicated point , list these interface in detail. Trainer和ParameterServer交互的接口 备选方案：1

    /* get Parameters */
    int32_t PullParameters(<map<block_id/*pname*/>*Tensor params>);
    
    /* set Parameters */
    int32_t UpdateParameters(<map<block_id/*pname*/>*Tensor params>，float32 leaningrate)

@helin

备选方案 ：2

    /* get Parameters */
    int32_t PullParameters(<map<string/*pname*/>*Tensor params);
      /* set Parameters */
    int32_t UpdateParameters(<map<string/*pname*/>*Tensor params)
    /* setup Update method，calculcate the learningrate policy in optimizer/updater module */
    void setUpdater(UpdaterBase)

其他深度学习框架使用了相似实现：mxnet ,

    /*   Given a key, assume x(left Tensor) is the received (pushed) value and y(right Tensor) is the value stored on the store node. The store updates y by `h(x, &y)`. The default h is ASSIGN, namely `*y = x`. */
    typedef std::function<void(Tensor& , Tensor*)> UpdaterFunction
    void setUpdater(UpdaterFunction)
    e.g.
    auto updater = [](Tensor& x, Tensor*y) {
      y -= x;
    }

@dzhwinter ParameterClient_CAPI C++调用Go ParameterClient library的接口函数

• 选1or2，update的方式
• 对于稀疏更新和正则化等更新的支持，是在ParameterServer端实现，还是在Trainer端实现？ *more important