Re: STL container question

From:

Ioannis Vranos <ivranos@no.spam.nospamfreemail.gr>

Newsgroups:

comp.lang.c++

Date:

Thu, 02 Oct 2008 16:31:30 +0300

Message-ID:

<gc2ifi$1h57$1@ulysses.noc.ntua.gr>

The program had a serious bug.

corrected:

Ioannis Vranos wrote:

Hendrik Schober wrote:

Ioannis Vranos wrote:

[...]
We must think generally. In general, sorting a list is faster than
sorting a vector, because the list sorting does not involve the
construction or destruction of any object.

Regarding ints, I think sorting a vector of ints and as list of ints,
both have about the same efficiency.

Why don't you just measure before you doubt the statements
of those who already went and did this?

On my platform, this

[ Non-portable code...]

and thus again disagrees with you.

Eagerly awaiting your counter example,

#include <iostream>
#include <ctime>
#include <vector>
#include <list>
#include <cstddef>
#include <algorithm>

class SomeClass
{
     typedef std::vector<int> TypeVector;

     TypeVector vec;

     enum { VectorSize= 1000 };

     public:

     SomeClass();

     bool operator<(const SomeClass &argSomeClass) const
     {
         return vec[0]< argSomeClass.vec[0];
     }
};

int main()
{
     using namespace std;

     srand(time(0));

     const size_t SIZE=10000;

     typedef vector<SomeClass> Vector;
     typedef list<SomeClass> List;

     cout<< "\nCreating vector with "<< SIZE<< " elements..."<< flush;
     Vector vec(SIZE);

     cout<<" Done!\n\n"<< flush;

===> List lis;

     cout<< "Filling list with vector elements..."<< flush;

     for(Vector::size_type i= 0; i< vec.size(); ++i)
         lis.push_back(vec[i]);

     cout<< " Done!\n\n"<< flush;

     clock_t timeBeginVector, timeEndVector, timeBeginList, timeEndList;

     cout<< "Timing the sorting of the vector..."<< flush;

     timeBeginVector= clock();

     sort(vec.begin(), vec.end());

     timeEndVector= clock();

     cout<< " Done!\n\n"<< flush;

     cout<< "Timing the sorting of the list..."<< flush;

     timeBeginList= clock();

     lis.sort();

     timeEndList= clock();

     cout<< " Done!\n\n"<< flush;

     cout<< "The sorting of the vector took "
         << static_cast<double>((timeEndVector- timeBeginVector))/
CLOCKS_PER_SEC
         << " seconds\n\n";

     cout<< "The sorting of the list took "
         << static_cast<double>((timeEndList- timeBeginList))/
CLOCKS_PER_SEC
         << " seconds\n\n";
}

SomeClass::SomeClass():vec(VectorSize)
{
     using namespace std;

     for(TypeVector::size_type i= 0; i< vec.size(); ++i)
         vec[i]= rand();

     sort(vec.begin(), vec.end());
}