c++ - 如何序列化 Armadillo 的 vector

Question

如何序列化 arma::Col ？下面是 MWE 和错误输出。

MWE:

#include <boost/mpi/environment.hpp>
#include <boost/mpi/communicator.hpp>
#include <iostream>
#include "armadillo"

namespace mpi = boost::mpi;

struct S
{   
    int i;
    arma::Col<double>::fixed<3> cvector;

    friend class boost::serialization::access;

    template<class Archive>
    void serialize(Archive& ar, const unsigned int version) 
    {
        ar& i;
        ar& cvector;
    }
};

int main()
{ 
    mpi::environment env;
    mpi::communicator world;

    S s;

    if (world.rank() == 0)
    {
        s.cvector[0] = 2;
        s.cvector[1] = 2;
        world.send(1, 0, s);
    }
    else
    {
        world.recv(0, 0, s);
        std::cout << s.cvector[0] << std::endl;
        std::cout << s.cvector[1] << std::endl;
    }

    return 0;
}

错误输出(跳过“required from”内容):

error: ‘class arma::Col<double>::fixed<3ull>’ has no member named ‘serialize’; did you mean ‘set_size’?
t.serialize(ar, file_version);

编辑: This帖子似乎与我的问题有关，不幸的是它没有得到回答。

Answer 1

这里问题的真正症结在于，您想向各种 Armadillo 对象添加一个 serialize() 成员函数，但这似乎不可能...除了谢谢在 Armadillo 中巧妙地使用预处理器，它是!

看看 Mat_bones.hpp 和 Col_bones.hpp...您会在 Mat< 的类定义中看到类似这样的内容 和 Col:

public:

#ifdef ARMA_EXTRA_COL_PROTO
  #include ARMA_INCFILE_WRAP(ARMA_EXTRA_COL_PROTO)
#endif

当我发现这个时，我非常高兴，因为现在我可以做一些事情，比如定义一个名为 Mat_extra_bones.hpp 的文件:

//! Add a serialization operator.
template<typename Archive>
void serialize(Archive& ar, const unsigned int version);

然后是 Mat_extra_meat.hpp:

// Add a serialization operator.
template<typename eT>
template<typename Archive>
void Mat<eT>::serialize(Archive& ar, const unsigned int /* version */)
{
  using boost::serialization::make_nvp;
  using boost::serialization::make_array;

  const uword old_n_elem = n_elem;

  // This is accurate from Armadillo 3.6.0 onwards.
  // We can't use BOOST_SERIALIZATION_NVP() because of the access::rw() call.
  ar & make_nvp("n_rows", access::rw(n_rows));
  ar & make_nvp("n_cols", access::rw(n_cols));
  ar & make_nvp("n_elem", access::rw(n_elem));
  ar & make_nvp("vec_state", access::rw(vec_state));

  // mem_state will always be 0 on load, so we don't need to save it.
  if (Archive::is_loading::value)
  {
    // Don't free if local memory is being used.
    if (mem_state == 0 && mem != NULL && old_n_elem > arma_config::mat_prealloc)
    {
      memory::release(access::rw(mem));
    }

    access::rw(mem_state) = 0;

    // We also need to allocate the memory we're using.
    init_cold();
  }

  ar & make_array(access::rwp(mem), n_elem);
}

那么，在你的程序中，你需要做的就是

#define ARMA_EXTRA_MAT_PROTO mat_extra_bones.hpp
#define ARMA_EXTRA_MAT_MEAT mat_extra_meat.hpp

serialize() 函数将成为 Mat 类的成员。您可以轻松地将此解决方案应用于其他 Armadillo 类型。

事实上，这正是 mlpack 库 ( http://www.mlpack.org/) 所做的，所以如果您有兴趣，可以仔细看看我在那里实现的确切解决方案:

https://github.com/mlpack/mlpack/tree/master/src/mlpack/core/arma_extend