UPDATED: I managed to get it to work after I googled around and read the doxygen comments in code. Problem was that I missed the cast before using resize() method and also not using std::ios::binary for the streams. If you want to do something similar, better check the answer by Azoth.
I am trying to serialize Eigen::Matrix type using Cereal. This is what I have (loosely based on https://gist.github.com/mtao/5798888 and the the types in cereal/types):
#include <cereal/cereal.hpp>
#include <cereal/archives/binary.hpp>
#include <Eigen/Dense>
#include <fstream>
namespace cereal
{
template <class Archive, class _Scalar, int _Rows, int _Cols, int _Options, int _MaxRows, int _MaxCols> inline
typename std::enable_if<traits::is_output_serializable<BinaryData<_Scalar>, Archive>::value, void>::type
save(Archive & ar, Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols> const & m)
{
int rows = m.rows();
int cols = m.cols();
ar(make_size_tag(static_cast<size_type>(rows * cols)));
ar(rows);
ar(cols);
ar(binary_data(m.data(), rows * cols * sizeof(_Scalar)));
}
template <class Archive, class _Scalar, int _Rows, int _Cols, int _Options, int _MaxRows, int _MaxCols> inline
typename std::enable_if<traits::is_input_serializable<BinaryData<_Scalar>, Archive>::value, void>::type
load(Archive & ar, Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols> const & m)
{
size_type size;
ar(make_size_tag(size));
int rows;
int cols;
ar(rows);
ar(cols);
const_cast<Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols> &>(m).resize(rows, cols);
ar(binary_data(const_cast<_Scalar *>(m.data()), static_cast<std::size_t>(size * sizeof(_Scalar))));
}
}
int main() {
Eigen::MatrixXd test = Eigen::MatrixXd::Random(10, 3);
std::ofstream out = std::ofstream("eigen.cereal", std::ios::binary);
cereal::BinaryOutputArchive archive_o(out);
archive_o(test);
std::cout << "test:" << std::endl << test << std::endl;
out.close();
Eigen::MatrixXd test_loaded;
std::ifstream in = std::ifstream("eigen.cereal", std::ios::binary);
cereal::BinaryInputArchive archive_i(in);
archive_i(test_loaded);
std::cout << "test loaded:" << std::endl << test_loaded << std::endl;
}
Your code is nearly correct but has a few mistakes:
You don't need to be making the size_tag since you are serializing the number of rows and columns explicitly. Generally cereal uses size_tag for resizable containers like vectors or lists. Even though the matrix can resize, it makes more sense just to serialize the rows and columns explicitly.
- Your load function should accept its parameter by non-const reference
- You shouldn't use operator= with the
std::ofstream objects
- It's better practice to let scoping and RAII handle closing/tearing down of the
std::ofstream as well as cereal archives (the binary archive will flush its contents immediately, but in general cereal archives are only guaranteed to flush their contents on destruction)
Here's a version that compiles and produces correct output under g++ and clang++:
#include <cereal/cereal.hpp>
#include <cereal/archives/binary.hpp>
#include <Eigen/Dense>
#include <fstream>
namespace cereal
{
template <class Archive, class _Scalar, int _Rows, int _Cols, int _Options, int _MaxRows, int _MaxCols> inline
typename std::enable_if<traits::is_output_serializable<BinaryData<_Scalar>, Archive>::value, void>::type
save(Archive & ar, Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols> const & m)
{
int32_t rows = m.rows();
int32_t cols = m.cols();
ar(rows);
ar(cols);
ar(binary_data(m.data(), rows * cols * sizeof(_Scalar)));
}
template <class Archive, class _Scalar, int _Rows, int _Cols, int _Options, int _MaxRows, int _MaxCols> inline
typename std::enable_if<traits::is_input_serializable<BinaryData<_Scalar>, Archive>::value, void>::type
load(Archive & ar, Eigen::Matrix<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols> & m)
{
int32_t rows;
int32_t cols;
ar(rows);
ar(cols);
m.resize(rows, cols);
ar(binary_data(m.data(), static_cast<std::size_t>(rows * cols * sizeof(_Scalar))));
}
}
int main() {
Eigen::MatrixXd test = Eigen::MatrixXd::Random(10, 3);
{
std::ofstream out("eigen.cereal", std::ios::binary);
cereal::BinaryOutputArchive archive_o(out);
archive_o(test);
}
std::cout << "test:" << std::endl << test << std::endl;
Eigen::MatrixXd test_loaded;
{
std::ifstream in("eigen.cereal", std::ios::binary);
cereal::BinaryInputArchive archive_i(in);
archive_i(test_loaded);
}
std::cout << "test loaded:" << std::endl << test_loaded << std::endl;
}
Based on @Azoth answer (whom I would like to give the whole credit, anyway), I improved the template a bit to
- work also for
Eigen::Array (rather than just Eigen::Matrix);
- not serialize compile-time dimensions (that makes quite some storage difference for e.g.
Eigen::Vector3f).
This is the result:
namespace cereal
{
template <class Archive, class Derived> inline
typename std::enable_if<traits::is_output_serializable<BinaryData<typename Derived::Scalar>, Archive>::value, void>::type
save(Archive & ar, Eigen::PlainObjectBase<Derived> const & m){
typedef Eigen::PlainObjectBase<Derived> ArrT;
if(ArrT::RowsAtCompileTime==Eigen::Dynamic) ar(m.rows());
if(ArrT::ColsAtCompileTime==Eigen::Dynamic) ar(m.cols());
ar(binary_data(m.data(),m.size()*sizeof(typename Derived::Scalar)));
}
template <class Archive, class Derived> inline
typename std::enable_if<traits::is_input_serializable<BinaryData<typename Derived::Scalar>, Archive>::value, void>::type
load(Archive & ar, Eigen::PlainObjectBase<Derived> & m){
typedef Eigen::PlainObjectBase<Derived> ArrT;
Eigen::Index rows=ArrT::RowsAtCompileTime, cols=ArrT::ColsAtCompileTime;
if(rows==Eigen::Dynamic) ar(rows);
if(cols==Eigen::Dynamic) ar(cols);
m.resize(rows,cols);
ar(binary_data(m.data(),static_cast<std::size_t>(rows*cols*sizeof(typename Derived::Scalar))));
}
}
