A howl on the wind…

(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.

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A performance benchmark of which method is faster of finding all unique elements of a vector. The goal is having an ordered container with just the unique elements, where the tested methods are std::sort()+std::unique()+erase(), versus inserting into a separate std::set, versus inserting into std::unordered_set and then into std::set, and finally inserting into boost::unordered_set and then into std::set.

Source for the integer version is speed-find-unique-int.cpp with cycle.h.

The compilers are Microsoft Visual C++ 2010 Express as VC10 with _SECURE_SCL disabled, and GNU g++ 4.3.2.

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//tinodidriksen.com/uploads/code/cpp/dynamic-string-box.cpp

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>

int main() {
    std::vector<std::string> strs;
    strs.push_back("Hello World!");
    strs.push_back("This is a text line.");
    strs.push_back("Shorter line.");

    size_t maxl = 0;
    for (size_t i = 0 ; i<strs.size() ; ++i) {
        maxl = std::max(maxl, strs[i].length());
    }

    std::cout << std::string(maxl+4, '*') << std::endl;
    for (size_t i = 0 ; i<strs.size() ; ++i) {
        std::cout << "* "
            << strs[i]
            << std::string(maxl-strs[i].length()+1, ' ')
            << "*" << std::endl;
    }
    std::cout << std::string(maxl+4, '*') << std::endl;
}

//tinodidriksen.com/uploads/code/cpp/sort-unique-vector.cpp

#include <vector>
#include <iostream>
#include <algorithm>

int main() {
    std::vector<int> vec1;
    vec1.push_back(1);
    vec1.push_back(2);
    vec1.push_back(3);
    vec1.push_back(1);
    vec1.push_back(2);
    vec1.push_back(3);
    vec1.push_back(1);

    std::sort(vec1.begin(), vec1.end());
    vec1.erase(std::unique(vec1.begin(), vec1.end()), vec1.end());

    std::cout << vec1.size() << std::endl;
    std::cout << vec1[0] << vec1[1] << vec1[2] << std::endl;
}

//tinodidriksen.com/uploads/code/cpp/vector-to-ostream.cpp

#include <ostream>
#include <iostream>
#include <vector>

template<typename T>
std::ostream& operator<<(std::ostream& stm, const std::vector<T>& obj) {
    stm << "[";
    if (!obj.empty()) {
        for (size_t i = 0 ; i<obj.size()-1 ; ++i) {
            stm << obj[i] << ",";
        }
        stm << obj.back();
    }
    stm << "]";
    return stm;
}

int main() {
    std::vector<int> vec;
    vec.push_back(1);
    vec.push_back(2);
    vec.push_back(3);
    vec.push_back(2);
    vec.push_back(5);
    vec.push_back(6);
    vec.push_back(1);
    std::cout << vec << std::endl;
}