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

From: Matthias Troyer (troyer_at_[hidden])
Date: 2007-02-08 12:53:18

On 1 Feb 2007, at 04:36, Hans Meine wrote:

> On Wednesday, 31. January 2007 22:54, Matthias Troyer wrote:
>> 1. approximate median and quantile estimators such as the p^2 methods
>> cannot be combined but are very important for some applications
>>
>> 2. accumulators for correlates samples, e.g. autocorrelation
>> estimators, or jackknife-bins cannot easily be combined. Instead of
>> just merging the results one has to store the results from the
>> individual accumulator_sets separately and combine them only in the
>> final evaluations. Please keep in mind that correlated samples are
>> very common.
>>
>> For 1. there is simply no way, and that is just it - one might either
>> have to make this cause a compile-time error or drop the median and
>> quantile estimators when combining.
>
> I'd say that a compile-time error would be perfectly OK.  It's just  
> that
> having a method for combining accumulators would open your library  
> up to many
> more applications.  (E.g., in my case I would be interested in  
> using it for
> image analysis, where I am using sort of accumulators for measuring
> properties of image regions, which are eventually merged.)
>
>> For 2. the problem is that
>> combined accumulator sets need a different data structure than
>> individual ones.
>
> I would be very happy if you found a way to integrate a simple way for
> combining soon, and postpone a solution of that latter problem.
>
> Right now, I don't think it would be impractical to require the  
> user of your
> library to specify in advance that additional data structures shall be
> maintained in case he/she wants to combine accumulators later.

A possible solution would indeed be to have a simple combine method  
for those accumulators where this is possible, and to work on a  
general solution later. This would immediately give the combine  
functionality to a part of the user community, while for the more  
demanding applications we have to wait.

Matthias