Re: [ublas] blocked products and relation UBLAS/GLAS

From: Gunter Winkler (guwi17_at_[hidden])
Date: 2006-02-16 05:01:35

Vardan Akopian wrote:

>A quick note and a question.
>For block matrices to be possible with ublas, we also need to make
>sure that there are no implicit assumptions of the element (scalar)
>product being commutative, i.e. a*b = b*a.
>Can anyone confirm or deny the presence for these kind of assumptions?
>  
>
Yes and no.

First, ublas always assumes that the product of two scalars is commuative.
Second, most algorithms does not use the fact. Over the last few years 
this issue was discussed several times, but we always decided to require 
products of scalars to be commutative because dropping this assumption 
would force us to check every algorithm whether it fails or not. This 
would be a lot of work and any volunteer is welcome ...

Personally, I would love to have a native ublas block sparse matrix - 
but I do not have the time to do the implementation. I think that GLAS 
will provide such classes, but I am not involved in this developement.

mfg
Gunter