Re: [boost] [Review] Review of the Accumulators library begins today, Jan 29

From: Eric Niebler (eric_at_[hidden])
Date: 2007-02-07 14:50:20

Cromwell Enage wrote:
>> What is your evaluation of the design?
> 
> Simple and straightforward.  Its extensibility is a
> big plus.  I am not a statistician, however, so I
> cannot judge its usability in that regard.
> 
> I'm curious about the design of weighted samples in an
> accumulator_set.  Can operations other than
> multiplication be applied to the weight?

Each accumulator is free to do anything with the weight parameter that 
it sees fit, including ignore it completely. But weighted samples have a 
well understood meaning in statistics, and giving it a different meaning 
would probably lead to confusion.

> I also echo John Maddock's request for pushing the
> elements of a sequence to an accumulator.  By logical
> extension, the ability to add objects of the same
> accumulator_set type together should be considered as
> well.

The first is a simple extension. The second, no less useful, is less 
simple, but not impossible, AFAIK.

>> What is your evaluation of the implementation?
> 
> Nicely done.  I'm sure it's first-rate.
> 
>> What is your evaluation of the documentation?
> 
> Aack.
> 
> In addition to the gentler introductory tutorial
> previously suggested by others, I would also like to
> see a motivation and/or rationale that is more
> explanatory than the "old adage", e.g. "Why Not Just A
> for Loop?" or "Going Beyond std::accumulate".

Agreed.

> Usually, I expect the reference documentation to be
> categorized by class and/or function instead of by
> header.  Staring at a long list of #includes, even as
> well organized as they are, does not raise my
> confidence in my ability to comprehend the inner
> workings of a library like this one.

I actually agree with this, but it's not a problem specific to the 
Accumulators reference section. I'm using the standard Doxygen/BoostBook 
integration that is part of Boost's documentation tool chain. It has 
been observed before that the header-based categorization is less than 
ideal, but nobody has stepped up to improve it. This would be an 
opportunity for someone to make a huge contribution to Boost. Takers?

>> What is your evaluation of the potential usefulness
>> of the library?
> 
> Even outside the field of statistics, I sense its
> great value in large-scale applications.  However, for
> small-scale programs (like the neural network example
> I recently added to my as-yet-unannounced automata
> library), it's hard to beat the equivalent for loops
> in terms of readability and efficiency.

Hand-coded loops are the gold-standard for performance, that's true, but 
ideally a higher-level abstraction should be more readable, not less. 
And templates let us have the abstraction without the penalty. IMO, it's 
a matter of familiarity. People new to STL might feel that a for-loop is 
more readable that a call to std::transform(), for instance, but not me.

>> Did you try to use the library?
> 
> Tried and succeeded.
> 
>> With what compiler?
> 
> GCC 3.4.5 (MinGW special)
> 
>> Did you have any problems?
> 
> Not at this time, no.
> 
>> How much effort did you put into your evaluation?
>> A glance?  A quick reading?  In-depth study?
> 
> I'd say a quick reading.  Enough to comprehend the
> tutorials, then a few excursions within the reference
> material.
> 
>> Are you knowledgeable about the problem domain?
> 
> I am familiar with the basics, so I'm not that
> intimidated by "kurtosis" and other finer details.
> 
>> Do you think the library should be accepted as a
>> Boost library?
> 
> The shape of its documentation is its biggest weakness
> right now, but it is outweighed by the robustness of
> its design.  I know that the documentation can be
> improved and I trust that it will be improved.  I vote
> yes.

Thanks, Cromwell.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com