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Question

I've been running various simulations with C++, and doing so has often involved saving lots of data to file (real/complex matrices, arrays, etc) and then reading them into other programs later. However, I have been unable to figure out a consistent and simple way of doing so. My solutions often involve several dozen lines of difficult-to-read code for each different kind of data structure that I want to save/read from a file. Are there any known libraries that can do this, or at least aid in the process? If there are any sort of matrix libraries that allow automatic saving/reading of matrices/vectors to file, that would also be helpful (Eigen does not have this option, as far as I can tell).

Answer

Cereal is a straight-forward and easy-to-use serialization library for C++ data structures. It knows all of the STL data structures and adapting custom classes for use with it is easy.

Example code:

#include <cereal/types/unordered_map.hpp>
#include <cereal/types/memory.hpp>
#include <cereal/archives/binary.hpp>
#include <fstream>
    
struct MyRecord
{
  uint8_t x, y;
  float z;
  
  template <class Archive>
  void serialize( Archive & ar )
  {
    ar( x, y, z );
  }
};
    
struct SomeData
{
  int32_t id;
  std::shared_ptr<std::unordered_map<uint32_t, MyRecord>> data;
  
  template <class Archive>
  void save( Archive & ar ) const
  {
    ar( data );
  }
      
  template <class Archive>
  void load( Archive & ar )
  {
    static int32_t idGen = 0;
    id = idGen++;
    ar( data );
  }
};
int main()
{
  std::ofstream os("out.cereal", std::ios::binary);
  cereal::BinaryOutputArchive archive( os );
  SomeData myData;
  archive( myData );
  return 0;
}