Re: Minimisation algorithm

From: Jim Phillips (jim_at_ks.uiuc.edu)
Date: Sun May 22 2011 - 14:49:16 CDT

Conjugate gradient only tells you what direction to find a minimum along
while the line search finds a minimum along that line. There are some
heuristics to reset the CG algorithm periodically as it's only useful if
the potential surface is nearly quadratic, and to avoid jumping out of the
local well when trying to bracket a minimum. The older velocity quenching
method is actually safer for fixing bad contacts in very large systems.

-Jim

On Fri, 20 May 2011, Christian Jorgensen wrote:

> Hi all, in the NAMD manual it says:
>
> "The default minimizer uses a sophisticated conjugate gradient and line
> search algorithm with much better performance than the older velocity
> quenching method".
>
> Could anyone elaborate a bit on this? Is it CGM via the Fletcher-Reeves
> algorithm? Where does the LS algorithm enter here and what would its
> role be when CGM is already employed?
>
> Thanks,
> Christian
>

This archive was generated by hypermail 2.1.6 : Wed Feb 29 2012 - 05:23:59 CST