Re: Fwd: output of correlator

[Jean-Noël Grad]

Hi,

maybe someone more knowledgeable can correct me, but I think what you're 
trying to achieve requires one correlator per particle.

Internally, ESPResSo correlators work with flattened array, therefore it 
is not possible to express all forms of Einstein notations. More 
specifically, the particle velocity observable returns a flat array 
internally, so for an observable of n particles, a vector of size 3*n is 
manipulated internally. The scalar product applied between two such 
3*n-dimensional vectors returns 1 value, which is why the VACF has shape 
(x, 1). The MSD has shape (x, n, 3) because it's a component-wise 
operation, and as such the number of particles can be used to re-shape 
the output.

Hope this helps,
JN

On 2022-08-04 16:42, Ahmad Reza Motezakker wrote:
> Sent from my iPhone
>
> Begin forwarded message:
>
> > From: Ahmad Reza Motezakker <armot@kth.se>
> > Date: 23 July 2022 at 16:27:01 CEST
> > To: espressomd-users@nongnu.org
> > Subject: output of correlator
>
> > 
> >
> > Dear Espressomd users,
> >
> > I am using correlator to get VACF of particles according to samples
> > diffusion_coefficient.py . In the sample we have one particle. But
> > in my case I have several particles but still the output.shape is
> > like (x,3). Is the final column the average of all particles or I am
> > doing something wrong? Thank you in advance for your help.
> >
> > P.S. I am using 4.1.4 version
> >
> > Best regards,
> >
> > Ahmad Reza