(C++) TestSpeedIndexingVersusIterators

 

A simple benchmark that tests the speed of incrementing each 2D-vector's elements. It compares the speed of doing so using indexing versus using iterators.

 

• Download the Qt Creator project 'TestSpeedIndexingVersusIterators' (version 1.0)(zip)
• Download the Windows executable of 'TestSpeedIndexingVersusIterators' (version 1.0)(zip)

 

 

 

 

 

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 12.10 (quantal)

IDE(s):

• Qt Creator 2.5.2

Project type:

• Console application

C++ standard:

• C++11

Compiler(s):

• G++ 4.7.2

Libraries used:

• STL: GNU ISO C++ Library, version 4.7.2

 

 

 

 

 

Qt project file: CppTestSpeedIndexingVersusIterators.pro

 

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TEMPLATE = app CONFIG += console CONFIG -= qt QMAKE_CXXFLAGS += -std=c++11 SOURCES += main.cpp

 

 

 

 

 

main.cpp

 

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#include <iostream> #include <vector> #include <boost/timer.hpp> ///From http://www.richelbilderbeek.nl/CppTestSpeedIndexingVersusIterators.htm int main() {   const int size = 5000;   const int nRepeat = 100;   std::vector<std::vector<int> > v(size,std::vector<int>(size));   double tIndexing = 0.0;   //Add nRepeat times 1 to each element using indexing   {     boost::timer t;     for (int i=0; i!=nRepeat; ++i)     {       for (int y=0; y!=size; ++y)       {         for (int x=0; x!=size; ++x)         {           ++v[y][x];         }       }     }     tIndexing = t.elapsed();   }   double tIterator = 0.0;   //Add nRepeat times 1 to each element using iterators   {     boost::timer t;     for (int i=0; i!=nRepeat; ++i)     {       const std::vector<std::vector<int> >::iterator rowIterEnd = v.end();       for (std::vector<std::vector<int> >::iterator rowIter = v.begin();         rowIter!=rowIterEnd;         ++rowIter)       {         const std::vector<int>::iterator colIterEnd = (*rowIter).end();         for (std::vector<int>::iterator colIter = (*rowIter).begin();           colIter!=colIterEnd;           ++colIter)         {           ++(*colIter);         }       }     }     tIterator = t.elapsed();   }   std::cout << "Time indexing: " << tIndexing     << "\tTime iterator: " << tIterator << std::endl;   std::cin.get(); }

 

 

 

 

 

Results

 

On a laptop (built in around 2011) with Lubuntu:

 

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Time indexing: 2.88 Time iterator: 2.51

 

On the same laptop (built in around 2011) with Lubuntu using Wine:

 

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Time indexing: 2.92 Time iterator: 2.58