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Subject: Re: [boost] [cpo-proposal] presentation of the idea
From: Santiago Tapia (santiago.tapia_at_[hidden])
Date: 2013-09-09 11:50:55


I have working in the implementation of the cpo library, so I keep working
and I expect to make a formal proposal within 2 or 3 months, and meanwhile
I will try my best to answer mails.

> Date: Wed, 28 Aug 2013 11:18:03 +0400
> From: Andrey Semashev <andrey.semashev_at_[hidden]>
> The storage strategy does not mandate the interface of the container.
> unordered_set/map are implemented as a number of buckets (i.e.
> single-linked lists), yet they provide sequence interface with an
> additional ability to iterate within a single bucket. I don't see why a
> similar approach couldn't be taken in your container.

I will not provide the classifier container with a push_back or push_front
method, instead I will use insert, I suppose it is just about the meaning
of sequence, I expect a sequence to keep an order on items while container
means just a collection of items in not a particular order.
On the other hand I will provide a way to iterate over a "single bucket".
Actually, I have been working on benchmarking and that seems to be the
better option to iterate over the classifier because it reduces the number of
virtual method calls in the iteration. I also will provide a const random
access iterator and some other utilities to access a particular item in the

> You can't create std::multiset<shape> but you can create
> boost::intrusive::multiset<shape>. The reason for that is that
> std::multiset attempts to allocate storage for shape, while
> boost::intrusive::multiset doesn't, leaving this to the user. This allows
> you to insert any objects derived from shape to the single
> boost::intrusive::multiset and work with this container pretty much the
> same way you would with std::multiset. You can even insert the very same
> object in multiple containers if you need to. I recommend you to have a
> look at Boost.Intrusive, it is a truly amazing library.

The interface for my library needs to be far more simple than the interface in
Boost.Intrusive, but I will consider that option to implement the details.
Up to now, I am only using std containers to avoid dependencies, but
I will consider other options to optimize speed and size performance.


About "polymorphic vector", that is, a container that stores different types
contigously, I should say that the interface needs to be as easy as in the
classifier, so I will discard solutions that needs any requirement to objects
apart from being copyable, default constructive or the like.

I will try to develop a prototype from Larry Evans' example (with his
permission). But because I am not an expert on alignment and memory
optimization, I will try to use something "more standard", actually I am
going trying to use the allocator to compute the "right" address to place
an object of a given type that is greater that a "free" memory pointer.
In that way, I also expect to take advantages of allocator such as
tbb cache aligned allocator.

Again, thank you all for your comments.



José Gutiérrez Abascal, 2 | 28006 Madrid
TEL +34 91 336 4266
E-MAIL stapia_at_[hidden]

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