Re: [boost] Boost pool allocator slower than STL allocator

31 Dec 2007

      Hi

I've been testing out boost pool allocator, and my results shows it's slower 
than the STL allocator. I'm using VSNet 2005 SP1. See test code below.

Also, on a separate issue, I notice the pool_allocator uses a singleton with 
static member in a function (Meyer's singleton). While this avoid the static 
construction issue, it does not free the memory until the application quits. 
This would work fine only POD data, if the dtor depends on a system in the 
application, it won't work. Shouldn't there be a pool allocator which can be 
used like the object_pool?

Robin

Test code
--------
With boost pool, timing on average is (0.03) vs STL (0.02) seconds in release 
mode. In debug mode, its boost (0.99) vs STL (0.8)

#include <boost/pool/pool_alloc.hpp>

#include <iostream>
#include <vector>

using namespace std;

class A
{
    int x, y;
public:
    A () : x (0), y (0)
    {}
};

#include <windows.h>

class Timer
{
public:
    Timer()
    {
        reset();
    }
    /// reset() makes the timer start over counting from 0.0 seconds.
    void reset()
    {
        unsigned __int64 pf;
        QueryPerformanceFrequency( (LARGE_INTEGER *)&pf );
        freq_ = 1.0 / (double)pf;
        QueryPerformanceCounter( (LARGE_INTEGER *)&baseTime_ );
    }
    /// seconds() returns the number of seconds (to very high resolution)
    /// elapsed since the timer was last created or reset().
    double seconds()
    {
        unsigned __int64 val;
        QueryPerformanceCounter( (LARGE_INTEGER *)&val );
        return (val - baseTime_) * freq_;
    }
    /// seconds() returns the number of milliseconds (to very high resolution)
    /// elapsed since the timer was last created or reset().
    double milliseconds()
    {
        return seconds() * 1000.0;
    }
private:
    double freq_;
    unsigned __int64 baseTime_;
};

int main ()
{
    Timer timer;

    for (int i = 0; i < 10; ++i)
    {
        // Switch allocators
        //        typedef vector <A> VectorA;
        typedef vector <A, boost::pool_allocator <A> > VectorA;

        VectorA vectorA;

        double startTime = timer.seconds ();
        for (int jj = 0; jj < 1000000; ++jj)
        {
            vectorA.push_back (A());
        }
        double endTime = timer.seconds ();

        cout << "Time taken is " << i << " - " << endTime - startTime << endl;
    }
    return 0;
}
...
On 30/12/2007, Robin <al@cyberversion.com> wrote:
...
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