[ODE] Faster ODE

[jnilson_99@yahoo.com]

Hi,

The mathematics behind what you're talking about
sounds really cool but over my head.

Do you know of any resource (web page or book) that
provides a background on LDLT, Lower Diagonal Lower
Transposed?

thanks,

john
--- Henri Hakl <henri@cs.sun.ac.za> wrote:
> Hi ODE :)
> 
> Please can somebody look at this and experiment with
> the file?
> 
> LDLT decomposition is one of the primary
> computational activities in ODE's physics engine.
> LDLT = Lower Diagonal Lower Transposed, meaning a
> constraint matrix A (that describes the physics of a
> world) can be decomposed into two matrices (L and D,
> where L is a lower triangular matrix (all entries
> above the diagonal are zero) and D is a diagonal
> matrix (all entries except the diagonal are zero)).
> Now  A = L D L'  (A equals the lower matrix times
> the diagonal matrix times the transposed lower
> matrix.) The A matrix varies in size and is
> typically between 10x10 and 500x500 for ODE
> (depending on
> how many constraints/collisions/etc need to be
> solved for a given simulation step).
> 
> This LDLT decomposition needs to be solved with
> every step and is quite computationally intensive.
> I've looked at the stldlt.c file that is part of the
> ODE source and it looks to me like it could be
> improved upon. Unforetunately I use Delphi, so I
> cannot test my suggested modifications directly
> (though the Delphi version seems fine and
> considerably faster then the original).
> 
> The file
> http://www.cs.sun.ac.za/~henri/fastldlt_henri.c is a
> replacement for fastldlt.c and should (barring
> errors) work flawlessly and faster then the
> original.
> 
> Let me know if it works, thanks :)
>   Henri
> 
> 


__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus – Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com