Re: hess(rosser())

[Juan Pablo Carbajal]

On Wed, Jul 4, 2012 at 6:36 PM, Jordi Gutiérrez Hermoso
<address@hidden> wrote:
> On 4 July 2012 12:25, Matyas Sustik <address@hidden> wrote:
>> So it seems that support for improved algorithms for symmetric matrices
>> could be done  by extending the existing framework.  It maybe not be that
>> large an undertaking.
>>
>> If any octave developers are reading this: I would consider implementing the
>> changes, please email me at address@hidden I may need some pointers on
>> how to handle symmetric/hermitian matrices. Also I do not wish to duplicate
>> an effort if someone else is already working on this.
>
> Please move this discussion to the maintainer's list.
>
> - Jordi G. H.

Hi,

I did some minimal work on manipulation of symmetric matrices (not
optimizing storage though).

- There are the functions vech and unvech (OF package general-1.3.1)
are for converting from (anti)symmetric to vector form
http://octave.svn.sf.net/viewvc/octave/trunk/octave-forge/main/general/inst/unvech.m?revision=10727&view=markup

- The function unvech has a subfunction sub2ind_tril (this one and
ind2sub_tril are also private in the OF package mechanics
http://octave.svn.sf.net/viewvc/octave/trunk/octave-forge/main/mechanics/inst/core/private/).
JordiGh gave me some ideas on how to implement this in the source code
of sub2ind and ind2sub functions, but I haven't done it yet. A short
explanation can be found in my TODO list in the wiki
http://octave.org/wiki/index.php?title=User:KaKiLa#extend_sub2ind_and_ind2sub

My two cents.

-- 
M. Sc. Juan Pablo Carbajal
-----
PhD Student
University of Zürich
http://ailab.ifi.uzh.ch/carbajal/