Why is this so much slower in C++?

Question

I have converted this simple method from C# to C++. It reads a path table and populates a list of lists of ints (or a vector of vectors of ints).

A sample line from

Answer 1

I profiled the code with Very Sleepy (Visual C++ 2010, 32-bit Windows XP). I don't know how similar my input data was, but here are the results anyway:

39% of the time was spent in basic_istream::operator>>

12% basic_iostream::basic_iostream

9% operator+

8% _Mutex::Mutex

5% getline

5% basic_stringbuf::_Init

4% locale::_Locimp::_Addfac

4% vector::reserve

4% basic_string::assign

3% operator delete

2% basic_Streambuf::basic_streambuf

1% Wcsxfrm

5% other functions

Some of the stuff seems to be from inlined calls so it's a bit difficult to say where it actually comes from. But you can still get the idea. The only thing that should do I/O here is getline and that takes only 5%. The rest is overhead from stream and string operations. C++ streams are slow as hell.