Cannot serialialize some double values

[dbaciu@…]

Hi,

The code sample below throws a "stream error" exception at line

ia >> double_back;

My development environment is Visual Studio 10, boost version 1.43. Sorry, I have not tried a newer version of boost.

The binary archive does not seem to handle doubles with lots of decimal places.

#include <boost/archive/binary_oarchive.hpp> #include <boost/archive/binary_iarchive.hpp>

void dummy()

{

string filename = "dummy.data";

double someDouble = 0.98123024735605502;

{

std::ofstream ofs; ofs.open(filename.c_str()); boost::archive::binary_oarchive oa(ofs); oa << someDouble;

}

double double_back; {

std::ifstream ifs; ifs.open(filename.c_str()); boost::archive::binary_iarchive ia(ifs); following throws a "stream error" exception ia >> double_back;

}

}

Thanks,

Dragos

[Robert Ramey]

I'm gueesing that is not an issue with the serialization library but rather floating point i/o when converting to text. Rework you example to use just standard stream i/o.

your test case .98123024735605502 has 17 significant decimal digits. This is approximatly 58 binary digits. Which shouldn't be a problem on an 80 bit IEEE754 implementation. But it could be a problem with a 64 bit implementation.

Also, some decimal fractional numbers might not be exactly representable in binary. This would lead to a truncation or rounding when he number is converted to binary. This would only be noticable on output.

I'm pretty sure I'm right here so I'm going to close this ticket.

Robert Ramey