Re: inline vector container

[Matt Benjamin <mbenjamin@redhat.com>]

Hi,

I think we should go with small_vector for this role, yes.  I found two issues.  First, there are critical defects in small_vector prior to boost 1.6.0.  Second, though it is header-only, the coupling with related version-specific boost types (container, allocator, respective detail types, and platform-specific selectors...) seems to make pulling it in separately pretty unrealistic as an option.  I looked at the cost of pulling in and selectively compiling (libs) an entire boost 1.6, and that went a lot easier (added less than a minute to my build time).

Matt

----- Original Message -----
> From: "Sage Weil" <sweil@redhat.com>
> To: "Allen Samuels" <Allen.Samuels@sandisk.com>
> Cc: ceph-devel@vger.kernel.org, mbenjami@redhat.com, cbodley@redhat.com
> Sent: Wednesday, February 3, 2016 3:04:57 PM
> Subject: Re: inline vector container
> 
> On Wed, 3 Feb 2016, Allen Samuels wrote:
> > One thing that the code base needs is a simple vector container that is
> > optimized for a small number of elements, i.e., for small element counts we
> > avoid the malloc/free overhead. But fully supports being resized into
> > larger
> > containers that are unbounded. Of course it will need to follow all of the
> > proper object copy/move semantics so that things like unique_ptr, etc work
> > correctly.
> > 
> > I heard rumors that there was one available in the boost world, but I can’t
> > seem to find it. Do you know about one being available?
> 
> http://www.boost.org/doc/libs/1_60_0/doc/html/boost/container/small_vector.html
> 
> > I’ve been prototyping one myself, just to get re-familiar with all of the
> > C++11 move sementics, and trivial constructors, etc.
> > 
> > The code is pretty complete, but the testing gets rather involved. There’s
> > no reason to contain this if it’s available elsewhere. But if it isn’t I
> > plan on continuing this…
> 
> I think Casey had prototyped something similar using a custom allocator,
> too, but I didn't actually look at the result.  And Matt talked about just
> pulling the boost one in-tree until we get updated boost in the supported
> distros, but I forget if he ran into problems there or not...
> 
> sage

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Matt Benjamin
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