Re: [boost] pool allocator question

From: Alexander Vushkan (alexander.vushkan_at_[hidden])
Date: 2007-08-15 05:17:08

Hi Steve.

On 8/15/07, Steve Kettle <skettle2000_at_[hidden]> wrote:
>
> I have a question about the memory pool allocation that boost
> implements.  Suppose we do the following:
>    std::vector<int, boost::pool_allocator<int> > v;
>    for (int i = 0; i < 10; ++i)
>      v.push_back(-1);
>
> And the std::vector<int> is implemented so that it starts out with
> reserved space of 1 and doubles space every time.  So At the end of the
> above loop v will have size 10 and reserved size 16.
>
> Does the boost allocator mean that there will memory arrays lieing
> around of size 1,2,4,8 that can be reused ?
>
> Eg if you do this:
>
>   std::vector<int, boost::pool_allocator<int> > v;
>    for (int i = 0; i < 10; ++i)
>      v.push_back(-1);
>
>   std::vector<int, boost::pool_allocator<int> > v2;
>    for (int i = 0; i < 8; ++i)
>      v2.push_back(-1);
>
> There will be no system call needed to get more memory -
> v2 will just reuse the memory in the pool_allocator<int> ?

No, it seems to me each allocator holds own piece.

-- 
with best wishes,
Alexander Vushkan