[ODE] biconjugate gradient

[Antonio_Martini at scee.net]

in  Baraff94('Fast contact force computation for...' , section 6.Dynamic
friction)  a unsymmetric contact matrix is generated in the dynamic
friction case. so i suppose  it's mainly down to the friction model
employed.

Antonio






"Alen Ladavac" <alenl-ml at croteam.com>@q12.org on 21/05/2004 09:16:44

Sent by:    ode-bounces at q12.org


To:    "Russ Smith" <russ at q12.org>
cc:    ode at q12.org
Subject:    Re: [ODE] biconjugate gradient


Now that you mention it... yes it does sound weird. While we are on the
quoting spree, the "Templates" paper by Barrett et al says:

"Few theoretical results are known about the convergence of BiCG. For
symmetric positive definite systems the method delivers the same
results as CG, but at twice the cost per iteration."

Guess the best person to ask that would be Mendoza, or some of the other
authors there. :)

Alen

----- Original Message -----
From: "Russ Smith" <russ at q12.org>
To: "Alen Ladavac" <alenl at croteam.com>
Cc: <ode at q12.org>
Sent: Thursday, May 20, 2004 22:50
Subject: [ODE] biconjugate gradient


>
> i was reading the paper by Mendoza, Laugier, and Faure ... they appear
> to make the claim that the biconjugate gradient method is better than
> plain 'ol conjugate gradient for near singular rigid body systems.
> i quote:
>
>   "matrix sparsity allows the use of a biconjugate gradient algorithm
>    [16], which iteratively refines a global solution even with singular
>    matrices"
>
> however: aren't the two methods equivalent when the matrix is symmetric?
> (as J*inv(M)*J' definitely is). why is mendoza using BiCG when it has a
> speed penalty but no advantage?
>
> russ.
>
> --
> Russell Smith
> http://www.q12.org
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> ODE mailing list
> ODE at q12.org
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>

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