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Subject: Re: [boost] New Boost.XInt Library, request preliminary review
From: Chad Nelson (chad.thecomfychair_at_[hidden])
Date: 2010-03-27 21:07:55

Hash: SHA1

>>> Have you looked at the (proposed) Boost.Move library by Ion (available
>>> from the sandbox)? [...]
>> No, I wasn't aware of its existence. I haven't seen it mentioned on this
>> list in the last couple weeks, is it under review for official
>> acceptance?
> AFAIK, it is in the review queue.

Ah, excellent. As soon as it's approved, I'll be happy to take advantage
of it.

> I understand your hesitation. [...] I think the advantages that move
> emulation has over copy-on-write (better performance, simpler
> implementation, thread safety) outweigh its disadvantages (the
> framework built around boost::rv<T> is still somewhat experimental),
> so I would urge you to take a look at it in the near future.

Certainly. It should allow XInt to run at copy-on-write speeds, even in
thread-safe mode -- a major improvement, and one that I'd jump at.

>>> Not sure what you're referring to by "suggestions that it relies on
>>> the compiler to somehow recognize it"...can you elaborate?
>> I finally tracked down the reference. From the "Thread Management"
>> documentation page of Boost.Thread: [...]
> Right, *containers* (not compilers) must detect that move emulation
> layer. So COW does have an additional advantage: better performance
> with non-move-aware containers.

Yes, exactly. I'm not sure what's involved with making a container
move-aware, but I'm fairly certain that the STL's containers aren't at
present. I don't know whether the Boost.Move library will suffer from
the same limitation.

> A suggestion (perhaps not a good one): replace the thread-safe
> implementation of xint::integer with a move-aware one, and allow either
> to be chosen via preprocessor defines.

If Boost.Move doesn't have the limitation mentioned above, then I'll
probably get rid of the copy-on-write stuff completely. It wouldn't have
any advantage that I can think of, at least for the moment.

> The choice of using COW or move emulation might be regarded more as an
> implementation issue, but (I'm guessing) will probably be brought up
> again during review.

I think I can defend the decision if it is. :-)

> I will try to take a look at the rest of the library shortly.

Thanks. I appreciate the feedback.
- --
Chad Nelson
Oak Circle Software, Inc.
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