Decimal precision truncated when serialize/deserialize std::vector<double> container

[zhoupengwei]

Hi author, I found that the std::vector lost precision during the process of deserializing, As the following sample code:

ryml::Tree tree;

  {
    std::vector<double> test_vec{1.23234412342131234,
                                 2.12323123143434237,
                                 3.67847983572591234};
    ryml::NodeRef root = tree.rootref();
    root |= ryml::SEQ;
    root << test_vec;
  }

  {
    ryml::ConstNodeRef root = tree.crootref();
    std::vector<double> test_vec;
    root >> test_vec;
    for (const auto& elem : test_vec) {
      std::cout << "elem " << elem << std::endl;
    }
  }

The program will output:
elem 1.23234
elem 2.12323
elem 3.67848

How can I avoid losing numerical accuracy ？

[biojppm]

TL;DR:
The loss happens only when serializing using the default operator<< in C++11 and C++14.

Use at least C++17 (because it provides std::to_chars()), or do the following:

        ryml::Tree serialized;
        ryml::NodeRef root = serialized.rootref();
        root |= ryml::SEQ;
        for(const double v : test_vec)
            root.append_child() << ryml::fmt::real(v, 17, ryml::FTOA_FLOAT);

For more details, see the linked PR, which adds an example and explanation to the quickstart.

[zhoupengwei]

@biojppm Thank you for providing detailed examples and great project.