Re: [Boost-users] custom allocators Re:pool_alloc

Subject: Re: [Boost-users] custom allocators Re:pool_alloc
From: Eric Whitcombe (ericwsf_at_[hidden])
Date: 2010-03-19 15:22:11

So.. have you modified STL code? Or is boost::pool some how able to 
reimplement std::set (or any STL container) node alllocation code? That 
would be quite a trick because, all else being equal, if all you are doing 
is providing your own allocator to an STL container you will not change how 
the container allocates it's internal implementation data structrures. You 
will only be changing how elements are allocated.

Eric

----- Original Message ----- 
From: "Filip Konvicka" <filip.konvicka_at_[hidden]>
To: <boost-users_at_[hidden]>
Sent: Friday, March 19, 2010 2:09 PM
Subject: Re: [Boost-users] custom allocators Re:pool_alloc

>> Sorry, if this is a little late to be helpful but I thought I'd add this
>> for historical purposes for anyone looking at this thread to deal with
>> their own problem. All STL containers use allocators to allocate and
>> initialize the memory to store the _elements_ in the container not the
>> node structure. The containers definition of the data structures that
>> support the implentation details are purely internal. The allocator
>> interface is paramterized on the type of the container element.
>
> In fact what I've done once is to have both the set object and the nodes 
> allocated in a kind of pool, and then just not call the destructor (just 
> have the set and its nodes disappear with the pool/pools). THAT is a 
> speed-up (otherwise a set gets years to destroy).
>
> Filip
>
>>>
>>> B Hart wrote:
>>>> Sorry, I don't get you...as I understand the pool is a singleton, and
>>>> once out of scope I would assume all the memory for the set is
>>>> released back to the OS. Therefore what is the purpose of
>>>> release_memory()...maybe I don't understand pool. And then "internal
>>>> node type"...what is that?
>>>>
>>>
>>> Set is implemented using a binary search tree. set<int>
>>> doesn't actually allocate ints, it allocates a struct that probably
>>> looks something like:
>>>
>>> struct Node {
>>> int value;
>>> int color;
>>> Node * left;
>>> Node * right;
>>> Nonde * parent;
>>> };
>>>
>>> pool_allocator uses separate singleton pools for
>>> each size of element that it needs to handle.
>>>
>>> In Christ,
>>> Steven Watanabe
>>>
>>> _______________________________________________
>>> Boost-users mailing list
>>> Boost-users_at_[hidden]
>>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>
>
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