The OPAL Discussion Forum

[Jochem Snuverink <jochem.snuverink AT psi.ch>]

Hi Anastasiya,

Is the calculation of your variable very complicated? If not you can 
calculate it perhaps in the input file directly? You have a few basic 
functions available in the EXPR part (sqrt, pow, exp, log, fabs, sin, 
etc., see https://gitlab.psi.ch/OPAL/Manual-2.0/wikis/optimiser) that 
you can use on the stat file variables.

The general case is however not possible at the moment. If it is a 
meaningful variable, we can possibly add it to the .stat file.

Alternatively, you can try to use the SYSTEM command 
(https://gitlab.psi.ch/OPAL/Manual-2.0/wikis/control) at the end of each 
run. This executes a system call, and if you do your calculation in a 
separate program and write it to file, you can read in this file again 
with "fromFile". This is untested, but I believe it should work.

hope this helps,
Jochem

On 27/06/18 21:19, Anastasiya Bershanska wrote:
> Hello,
>
> I have a questions on the optimizer. According to the documentation, EXPR in 
> OBJECTIVE and CONSTRAINT can be specified using a few built-in functions that 
> take data from .stat file and variables defined in the temple file. However, 
> I would like to be able to optimize with respect to a variable that I 
> calculate using .stat and/or .dat files (i.e. specify OBJECTIVE as a new 
> function of input files). Is it possible to specify an new function that 
> reads from output files within OPAL input temple file?
>
> Thank you,
> Anastasiya