A howl on the wind…

(There is also an opposite int-to-string performance test.)

(Updated 2010-04-15: Re-run with g++ 4.4.1 and VC++ 2010 Express; updated tables to show both ticks and relative factor, instead of just percentage of baseline.)

A performance benchmark of which method is faster of converting an std::string to an integer. The goal is ending up with an integer with the value represented in an std::string.

The tested methods are:

• atoi()
• atol()
• strtol()
• std::stringstream
• std::stringstream, reusing the object
• boost::lexical_cast<int>()
• a hand-written naive loop

Source for the test is at speed-string-to-int.cpp with cycle.h.

The compilers are Microsoft Visual C++ 2010 Express as VC10 with _SECURE_SCL disabled, GNU g++ 4.4.1, and LLVM clang++ from svn.

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(There is also an opposite string-to-int performance test.)
(Updated 2011-02-05: Added a hand-made function as baseline; re-run all tests, and with new clang++ from svn)

A performance benchmark of which method is faster of converting an integer to an std::string. The goal is ending up with an std::string representation of the input integer.

The tested methods are:

• naive loop into a std::string
• sprintf() into a char[] buffer, then std::string(buffer)
• snprintf() into a char[] buffer, then std::string(buffer)
• sprintf() into &std::string[0], and .resize() to fit
• snprintf() into &std::string[0], and .resize() to fit
• output to a std::stringstream, then std::string = stream.str()
• as above, but reusing the stringstream object
• std::strstream(&string[0]) then .resize(stream.pcount())
• std::string = boost::lexical_cast<std::string>()
• Boost.Spirit.Karma generate into a char[] buffer, then std::string(buffer)

Source for the test is at speed-convert-int-to-string.cpp with cycle.h.

The compilers are Microsoft Visual C++ 2010 Express as VC10 with _SECURE_SCL disabled, GNU g++ 4.4.1, and clang++ from svn.

Continue Reading »