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Re: [Opal] quaternion isn't unit quaternion. Norm: -nan

From: Christopher Pierce <cmpierce AT uchicago.edu>
To: Adelmann Andreas <andreas.adelmann AT psi.ch>
Cc: "opal AT lists.psi.ch" <opal AT lists.psi.ch>
Subject: Re: [Opal] quaternion isn't unit quaternion. Norm: -nan
Date: Thu, 6 Apr 2023 19:29:42 +0000
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Ahh, Ok. Yes, the fieldmap really is a strange one.

Yeah, if it would be difficult to make things work correctly when Ez=0 through the whole file, then some sort of error message mentioning the problem would probably be a good solution. Setting Ez to like 0.00000001 really shouldn't affect the results.

Cheers,

Chris

From: Adelmann Andreas <andreas.adelmann AT psi.ch>
Sent: Thursday, April 6, 2023 9:24 AM
To: Christopher Pierce <cmpierce AT uchicago.edu>
Cc: opal AT lists.psi.ch <opal AT lists.psi.ch>
Subject: Re: [Opal] quaternion isn't unit quaternion. Norm: -nan

Hi Chris, with the latest developer version I get the same error.

All field components zero, I view as a pathological case and also understand

why the error (exception) occurs. The way you “fixed” this is to me a good

path forwards.

In case you disagree, I can open an issue, otherwise I would try to create

a better message to the use, in such a situation.

What do you think?

Cheers A
------
Dr. sc. math. Andreas (Andy) Adelmann
Head a.i. Labor for Scientific Computing and Modelling
Paul Scherrer Institut OHSA/D09 CH-5232 Villigen PSI
Phone Office: xx41 56 310 42 33 Fax: xx41 56 310 31 91
Zoom ID: 470-582-4086 Password: AdA
Zoom Link: https://ethz.zoom.us/j/4705824086?pwd=dFcvT1pMMGY0bHg0dTNncUNZZTJkZz09

-------------------------------------------------------
Friday: ETH HPK G 28 +41 44 633 3076
============================================
The more exotic, the more abstract the knowledge,
the more profound will be its consequences.
Leon Lederman
============================================

On 4 Apr 2023, at 19:58, Christopher Pierce <cmpierce AT uchicago.edu> wrote:

Huh, interesting. I am using version 2022.1.0 (git rev. a4e0e14466557289b4f7a843fb9eb72700ff1992). Is that the development version that doesn't show the error?

Cheers,

Chris

From: Adelmann Andreas <andreas.adelmann AT psi.ch>
Sent: Tuesday, April 4, 2023 5:44 AM
To: Christopher Pierce <cmpierce AT uchicago.edu>
Cc: opal AT lists.psi.ch <opal AT lists.psi.ch>
Subject: Re: [Opal] quaternion isn't unit quaternion. Norm: -nan

Hi Chris great that OPAL is of help to your research!

And yes your original field map is special :), indeed.

I can reproduce and confirm that with a small Ez component OPAL is

running well. I do not see however, the error you encountering. What version of OPAL

are you using?

Cheers A
------
Dr. sc. math. Andreas (Andy) Adelmann
Head a.i. Labor for Scientific Computing and Modelling
Paul Scherrer Institut OHSA/D09 CH-5232 Villigen PSI
Phone Office: xx41 56 310 42 33 Fax: xx41 56 310 31 91
Zoom ID: 470-582-4086 Password: AdA
Zoom Link: https://ethz.zoom.us/j/4705824086?pwd=dFcvT1pMMGY0bHg0dTNncUNZZTJkZz09

-------------------------------------------------------
Friday: ETH HPK G 28 +41 44 633 3076
============================================
The more exotic, the more abstract the knowledge,
the more profound will be its consequences.
Leon Lederman
============================================

On 4 Apr 2023, at 05:53, Christopher Pierce <cmpierce AT uchicago.edu> wrote:

Hey folks,

First, I have recently started using opal and wanted to thank you for it. It looks like it will be very useful for my research.

I am emailing because I am running into a problem with the attached input file. It is supposed to represent a beam in a artificial electrostatic focusing channel. I do this by loading a fieldmap into the simulation with a constant negative radially pointing E-field and no Ez component.

The problem I encounter is that after loading the input file, the program returns the error "quaternion isn't unit quaternion. Norm: -nan".

I found out that I can make the error go away by setting a single element of the fieldmap to have finite Ez (also attaching the file as "e-lens-fixed.T7". This fieldmap seems to give me the results I expect. Is there something that I am doing wrong here?

Cheers,

Chris Pierce
<20230403-opal-focusing-channel.txt><e-lens.T7><e-lens-fixed.T7>

[Opal] quaternion isn't unit quaternion. Norm: -nan, Christopher Pierce, 04/04/2023
- Re: [Opal] quaternion isn't unit quaternion. Norm: -nan, Adelmann Andreas, 04/04/2023
  - Re: [Opal] quaternion isn't unit quaternion. Norm: -nan, Christopher Pierce, 04/04/2023
    - Re: [Opal] quaternion isn't unit quaternion. Norm: -nan, Adelmann Andreas, 04/06/2023
      - Re: [Opal] quaternion isn't unit quaternion. Norm: -nan, Christopher Pierce, 04/06/2023
        
        Re: [Opal] quaternion isn't unit quaternion. Norm: -nan, Adelmann Andreas, 04/07/2023
        
        Re: [Opal] quaternion isn't unit quaternion. Norm: -nan, Christopher Pierce, 04/11/2023