Boost C++ Libraries

These performance measurements are centered around formatting of a sequence of different items, including 2 double floating point numbers using different libraries and methods. The overall execution times for those examples are compared below. We compare using sprintf, C++ iostreams, Boost.Format, and Spirit.Karma.

For the full source code of the performance test please see here: format_performance.cpp. All the measurements have been done by doing 1e6 iterations for each formatting type (NUMITERATIONS is set to 1e6).

Code used to measure the performance for sprintf:

char buffer[256];
for (int i = 0; i < NUMITERATIONS; ++i) {
    sprintf(buffer, "[%-14.3f%-14.3f]", 12345.12345, 12345.12345);
}

Code used to measure the performance for standard iostreams:

std::stringstream strm;
for (int i = 0; i < NUMITERATIONS; ++i) {
    strm.str("");
    strm << '['
      << std::setiosflags(std::ios::fixed)
      << std::left
      << std::setprecision(3)
      << std::setw(14)
      << 12345.12345
      << std::setw(14)
      << 12345.12345
      << ']';
}

Code used to measure the performance for Boost.Format:

std::string generated;
boost::format outformat("[%-14.3f%-14.3f]");
for (int i = 0; i < NUMITERATIONS; ++i)
    generated = boost::str(outformat % 12345.12345 % 12345.12345);

The following code shows the common definitions used by all Spirit.Karma performance measurements as listed below:

template <typename T>
struct double3_policy : boost::spirit::karma::real_policies<T>
{
    //  we want to generate up to 3 fractional digits
    static unsigned int precision(T) { return 3; }
};

typedef boost::spirit::karma::real_generator<double, double3_policy<double> >
    double3_type;
double3_type const double3 = double3_type();

Code used to measure the performance for Spirit.Karma using a plain character buffer:

char buffer[256];
for (int i = 0; i < NUMITERATIONS; ++i) {
    char *p = buffer;
    generate(p
      , '[' << left_align(14)[double3] << left_align(14)[double3] << ']'
      , 12345.12345, 12345.12345);
    *p = '\0';
}

The following table shows the overall performance results collected while using different compilers. All times are in seconds measured for 1e6 iterations (platform: Windows7, Intel Core Duo(tm) Processor, 2.8GHz, 4GByte RAM). For a more readable comparison of the results see this figure.

Figure 5. Performance comparison for a sequence of several items