Re: [ublas] Fast small matrices / homogeneous matrices with uBlas

Subject: Re: [ublas] Fast small matrices / homogeneous matrices with uBlas
From: Riccardo Rossi (rrossi_at_[hidden])
Date: 2010-08-09 07:24:04

Dear Nasos,

     just to add my cent to the discussion ... do you believe there is
any hope that the tiny matrix and vectors can be used as "scalar types"
in the construction of matrices and vectors?

for example
matrix < TinyMatrix<3,3> > 

i know there was long ago a discussion on this issue, but i guess the
new design would give the right opportunity to think about this
possibility...

anyway
thank you for the attention
Riccardo

-- 
________________________________________________________________
Riccardo Rossi, Ph.D, Civil Engineer
member of the Kratos Group: kratos.cimne.upc.es
Centro Internacional de Métodos Numéricos en Ingeniería (CIMNE)
Universidad Politécnica de Cataluña (UPC)
Edificio C-1, campus Norte UPC
Gran Capitan, s/n
08034 Barcelona, España
Tel. [phone]
________________________________________________________________
AVISO IMPORTANTE
Los datos de carácter personal contenidos en el mensaje, se registrarán
en un fichero para facilitar la gestión de las comunicaciones de CIMNE.
Se pueden ejercitar los derechos de acceso, rectificación, cancelación y
oposición por escrito, dirigiéndose a nuestras oficinas de CIMNE, Gran
Capitán s/n,  Edificio C1 - Campus Norte UPC, 08034 Barcelona, España.
AVÍS IMPORTANT
Les dades de carà cter personal contingudes en aquest missatge es
registraran en un fitxer per facilitar la gestió de les comunicacions
del CIMNE. Es poden exercir els drets d'accés, rectificació,
cancel·lació i oposició, per escrit a les nostres oficines del CIMNE,
Gran Capità s/n, Edifici C1, Campus Nord UPC, 08034 Barcelona, Espanya.
IMPORTANT NOTICE
All personal data contained in this mail will be processed
confidentially and stored in a file property of CIMNE in order to manage
corporate communications. You may exercise the right of access,
rectification, deletion and objection by letter sent to CIMNE, Gran
Capitán, Edificio C1 - Campus Norte UPC, 08034 Barcelona, Spain.
On Mon, 2010-08-09 at 07:20 -0400, Nasos Iliopoulos wrote:
> Thomas,
> There is an active discussion and a proposal that will bring fixed
> vector and fixed matrices (appropriate for small containers) into
> uBlas. My feeling is that it is getting to a good shape and will
> probably make it into the next release. Follow this post for some
> code:
> 
> http://lists.boost.org/MailArchives/ublas/2010/07/4500.php
> 
> > And secondly, it cannot use the matrices structure such as the fact
> > that the last line of an homogenous
> > matrix never changes.
> 
> Although this is the case with some applications (and even some
> graphics API providers, like AMD), there are applications that fixing
> the last row is not desirable (i.e. when you do projections and expect
> to use the w component of your 4 vector prior to perspective
> division). I suppose uBlas will support fixed containers in the
> future, but I find unlikely that it will make any assumptions like
> homogeneity (in which case you just need to divide by the last
> element, if you mean to retrieve 3D points).
> 
> Best
> Nasos
> 
> 
> > Date: Mon, 9 Aug 2010 11:32:27 +0900
> > From: thomas.moulard_at_[hidden]
> > To: ublas_at_[hidden]
> > CC: fbleibel_at_[hidden]; florent_at_[hidden]
> > Subject: [ublas] Fast small matrices / homogeneous matrices with
> uBlas
> > 
> > Hello everyone,
> > I am currently evaluating the possibility for uBlas to have a better
> > support for small matrices.
> > In particular, 3d transformation matrices represented by homogenous
> matrices.
> > 
> > First, I have seen that uBlas is slower than libraries specifically
> > targeted for small matrices like tvmet.
> > And secondly, it cannot use the matrices structure such as the fact
> > that the last line of an homogenous
> > matrix never changes.
> > 
> > I was wondering if anyone here would have tried to tackle these
> problems?
> > 
> > Any advice would be greatly appreciated,
> > --
> > Thomas Moulard
> > _______________________________________________
> > ublas mailing list
> > ublas_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/ublas
> > Sent to: nasos_i_at_[hidden]
> _______________________________________________
> ublas mailing list
> ublas_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/ublas
> Sent to: rrossi_at_[hidden]