Re: Can I avoid the use of arrays in this situation or do I have to use them?

On Nov 24, 1:24 am, mike3 <mike4...@yahoo.com> wrote:


I wrote a little test using VecStack I mentioned below. One
has to consider that the test ran in a single threaded
environment and things may change if you throw a
critical section in there (but not to much if not
contented). I used Dev C++ (don't know which STL),
turned debugging off and enabled optimization for
speed. Turned out the vector code executed faster
than the array code by +10 seconds for 30000000
items. Test is below:

#include <iostream>
#include <cassert>
#include <vector>
#include <memory>
//...#include "yourMutex.h"

template <class T>
struct VecStack
{
  typedef std::auto_ptr<std::vector<T> > ClientItem;

  VecStack( unsigned defaultSz )
  : defaultSz_( defaultSz )
  { vecList_.reserve( 50 ); }

  ClientItem pop()
  {
    //...Mutex::guard lock( mutex_ );
    std::auto_ptr<std::vector<T> > v( 0 );

    if( vecList_.empty() )
    {
      v.reset( new std::vector<T>( defaultSz_ ) );
    }
    else
    {
      v.reset( vecList_.back() );
      vecList_.pop_back();
    }
    return v;
  }

  void push( ClientItem v )
  {
    //...Mutex::guard lock( mutex_ );
    //assert( v.get() );
    vecList_.push_back( v.release() );
  }

  private:
    std::vector<std::vector<T>*> vecList_;
    unsigned defaultSz_;
    //...Mutex mutex_;

};

enum
{
  eMAX_EXPECTED_SZ = 512,
  eLOOP_SZ = 30000000,
  eINNER_SZ = 500
};

void testVect1( unsigned len )
{
  typedef VecStack<int> StackType;
  static StackType stack( eMAX_EXPECTED_SZ );

  StackType::ClientItem item = stack.pop();
  item->resize( len );
  stack.push( item );
}
void testVect2( unsigned len )
{
  int Items[eMAX_EXPECTED_SZ] = { 0 };
}
void doTest( void(*op)(unsigned) )
{
  for( int i = 0; i < eLOOP_SZ/eINNER_SZ; ++i )
  {
    for( int j = 0; j < eINNER_SZ; ++j )
    {
      (*op)( j );
    }
  }
}

int main(int argc, char *argv[])
{
  std::cout << "Press key to start test!" << std::endl;
  std::cin.get();
  std::cout << "Test1 running...\n";
  doTest( testVect1 );
  std::cout << "Test2 running... \n";
  doTest( testVect2 );
  std::cout << "End... Press key to exit." << std::endl;
  std::cin.get();
  return EXIT_SUCCESS;
}

Kind regards,

Werner