Re: replica_bias and colvars

From: JC Gumbart (gumbart_at_physics.gatech.edu)
Date: Thu Aug 10 2017 - 16:17:21 CDT

Z is the name of the harmonic restraint.

For reference, the colvar is in a different file:

harmonic {
name Z
colvars COMDistance
forceConstant { 0.0125 } centers { 0.0 }
}

But the replica(colvarbias.$i) is how the script tells namd to update that
replica's properties. I wondered if something has changed in how namd
interprets that data.

Thanks!
JC

On Thu, Aug 10, 2017, 1:58 PM Vermaas, Joshua <Joshua.Vermaas_at_nrel.gov>
wrote:

> The old way would have been through something like "eval colvarbias [cat
> changeconfig somestuff here]". I ran into problems once when I neglected to
> change the name of the harmonic bias I wanted to change (I call all of mine
> harm), accidentally using the collective variable the harmonic was trying
> to bias as the name instead. Is "Z" the name of your collective variable or
> the harmonic that biases the collective variable?
>
> -Josh
>
> On 08/10/2017 11:54 AM, Giacomo Fiorin wrote:
> Hi JC, how is this code calling Colvars? I don't see any Tcl command that
> does call it in there.
>
> The primary method for changing parameters for a bias should be through
> the "cv" command. Deleting the bias and re-creating it with the new
> configuration would be the way to go.
>
> Giacomo
>
> On Thu, Aug 10, 2017 at 1:07 PM, JC Gumbart <gumbart_at_physics.gatech.edu
> <mailto:gumbart_at_physics.gatech.edu>> wrote:
> Has something changed in newer versions of NAMD with regards to how inputs
> are fed to different replicas in colvars?
>
> Specifically, the input below worked fine in earlier versions (2.10 I
> think?), but in 2.12, the center and forceConstant both get set to the same
> value, namely that for the center.
>
> > proc replica_bias { i } {
> > set c [expr 5.5 + $i*0.5]
> > set klist { 10 10 10 10 10 10 5 5 5 5 5 5 5 5 5 5 5 5 5 5 }
> > set k [expr [lindex $klist $i]*0.05*0.05]
> > return [list Z "centers \{$c\} forceConstant \{$k\}"]
> > }
>
> And then this is how that proc is used:
> > set replica(colvarbias) [replica_bias $replica(index)]
> > for { set i 0 } { $i < $replica(num_neighbors) } { incr i } {
> > set replica(colvarbias.$i) [replica_bias $replica(index.$i)]
> > set replica(colvarbias.$i) [replica_bias $replica(index.$i)]
> > }
>
>
> Thanks!
> JC
>
>
>
>
> --
> Giacomo Fiorin
> Associate Professor of Research, Temple University, Philadelphia, PA
> Contractor, National Institutes of Health, Bethesda, MD
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