[gpaw-users] bfgs line search

[Jess Wellendorff]

Hi Sampsa,

yes, the BFGSLineSearch algorithm tries to avoid taking "bad" steps 
during structure relaxation, so it looks around in the potential-energy 
landscape before deciding on the next step to take.
Therefore, each relaxation step will often be preceded by several 
electronic structure calculations.

NB: Since the BFGSLineSearch algorithm relies on an accurate "picture" 
of the surrounding potential-energy landscape, it is important to employ 
well-converged electronic structures.
Otherwise the algorithm may get the wrong impression of which step to take.
This appears to be the case in the example you have provided. The 
algorithm is supposed to only take steps that will lead to a smaller 
total energy than that of the preceding step. This has clearly failed.

Best
- Jess Wellendorff

On 05/17/2012 04:38 PM, Sampsa Riikonen wrote:
> Dear List,
>
> This is a weird detail of ASE behaviour..
>
> For the optimization of a small molecule, aserun.log looks like this:
> ---------
> cat aserun.log
>
> BFGSLineSearch:   0  15:32:19       -6.000802       0.0392
> BFGSLineSearch:   1  15:33:29       -6.000746       0.0266
> BFGSLineSearch:   2  15:34:32       -6.000747       0.0337
> BFGSLineSearch:   3  15:35:22       -6.000710       0.0375
> BFGSLineSearch:   4  15:36:04       -6.000737       0.0188
>
> ----------
>
> aserun.out has the following:
> ----------
> grep -i "converged" aserun.out
>
> Converged After 32 Iterations.
> Converged After 17 Iterations.
> Converged After 17 Iterations.
> Converged After 20 Iterations.
> Converged After 4 Iterations.
> Converged After 3 Iterations.
> Converged After 19 Iterations.
> Converged After 13 Iterations.
> Converged After 3 Iterations.
> Converged After 9 Iterations.
> Converged After 8 Iterations.
> Converged After 3 Iterations.
> Converged After 3 Iterations.
> Converged After 14 Iterations.
> Converged After 13 Iterations.
> Converged After 6 Iterations.
> Converged After 4 Iterations.
> Converged After 3 Iterations.
> Converged After 3 Iterations.
> Converged After 3 Iterations.
> Converged After 13 Iterations.
> Converged After 14 Iterations.
> Converged After 10 Iterations
> ----------
>
> So, gpaw has calculated the electronic structure for quite many
> geometries, while bfgs line search only
> reports 5 steps.
>
> Does it report only successive "line minizations" and nothing else?
>
> Regards,
>
> Sampsa
>
>
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