Re: [Boost-users] Accumulators: Using data vector from Interprocess

Subject: Re: [Boost-users] Accumulators: Using data vector from Interprocess
From: Eric Niebler (eric_at_[hidden])
Date: 2008-12-23 13:14:00

John Phillips wrote:
> dhruva wrote:
>> Hi,
>>  I have large data to be processed hence planning to use memory mapped
>> file backed vector from boost::interprocess. Could I use this vector
>> directly in accumulators and perform computations on data in the
>> boost::interprocess container without having to copy it all into the
>> contain in accumulator_set?
>>
>>  Also, is there a way to remove an entry once I add it to an
>> accumulator_set? I want to emulate a sliding window calculation. Ex:
>> If my window size is 100, when I add the 101st entry, I want to remove
>> the 1st entry so that the size is always 100.
>>
> You can use an accumulator with any container that allows you to walk 
> through the contained values, so it will work with this one. Most 
> accumulators don't store any of the data points, and the ones that do 
> store any, don't store all. So, in general you will not be making a copy 
> of all the data.

Correct, thanks John.

> For the moving average on a widow, the accumulators library doesn't 
> currently include an accumulator that does this so a custom accumulator 
> has to be defined. However, you might look in the sandbox and see if one 
> is there. I don't recall who did it, but I remember a discussion about 
> making one of these in the past. I think there is an available version 
> somewhere.

Also correct. A moving average accumulator is an often requested 
feature. I knocked one together as a proof-of-concept during the 
accumulators review, but never polished it. You can find it in this message:

http://lists.boost.org/Archives/boost/2007/07/124979.php

HTH,

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com