Re: [ublas] vectors

From: Yoder, Jeffrey - SSD (Jeffrey.Yoder_at_[hidden])
Date: 2006-11-17 08:01:16

Thanks for the insight.  That all makes sense.  This came up when I was
adding boost serialization to a class and got: error C2039: 'serialize'
: is not a member of 'std::vector<_Ty>'.

I thought this meant I needed to use boost vectors so I switched to them
but found my push_back method then wouldn't compile.  As it turns out,
all I needed to do was add #include <boost/serialization/vector.hpp> and
the std::vector works fine.

Thanks again for your response Michael!

-----Original Message-----
From: ublas-bounces_at_[hidden]
[mailto:ublas-bounces_at_[hidden]] On Behalf Of Michael Stevens
Sent: Thursday, November 16, 2006 4:43 PM
To: ublas mailing list
Subject: Re: [ublas] vectors

Jeff,

On Thursday, 16. November 2006 19:18, Yoder, Jeffrey - SSD wrote:
> Why don't boost vectors offer a push or push_back type method?  It
seems
> odd to require external maintenance of the current vector size, or the
> use of a separate call to a size method, or creation of an iterator
just
> to add a value to the end of the vector.

The informal reason is that dense uBLAS vectors are not STL vectors,
they just 
happen to have the same name!

An STL vector provide indexible storage with an efficient growth
stratergy for 
appended element. The later requires the notion of capacity and storage 
doubling when the current capacity is exceeded.

A uBLAS vector provide indexible storage with an algebraic size (the
size in a 
linear algebra expression) that is identical to storage capacity
required.

Without adding the notion of capacity you cannot implement the push
functions 
with the same semantics as STL does. If we wanted such a function for
ease of 
use it would be better to call it something else to avoid confusion!

-- 
___________________________________
Michael Stevens Systems Engineering
34128 Kassel, Germany
Phone/Fax: [phone]
Navigation Systems, Estimation  and
                 Bayesian Filtering
    http://bayesclasses.sf.net
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