[Difx-users] DIFXCalc max number of antenna

[Walter Brisken]

Hi Chris, Olaf,

It would be good to explicitly reach out to David Gordon on this for two 
reasons:

1. would be good that any changes made are captured upstream and that our 
usage envelope is understood by David

2. would be good to know if there are any dangers associated with 
increasing values and we might identify other limits that should be raised

Thanks for identifying this issue,

Walter

On Thu, 14 Jun 2018, Olaf Wucknitz wrote:

> Hi Chris,
>
> On Thu, 14 Jun 2018, Chris.Phillips at csiro.au wrote:
>
>>  I just increased the size of these parameters to 41 (looks like it is
>>  #antenna + centre of earth) and can now successfully run difxcalc with 36
>>  antenna.  It now seems to run fine.
>>
>>  I noted that it looks like max # scans is 500, which feels a little too
>>  small for my liking (I guess if you run DIFX in subjobs, this is less of
>>  an issue).
>>
>>  I can push these changes back to subversion if it is thought to be a
>>  reasonable increase.
>
> increasing the numbers is a good idea. Can you maybe also add a brief summary 
> of the limits that you know of in a few lines in one of the files (or a new 
> one)?
>
> I guess a higher number for the antennas would be useful. I am using difxcalc 
> for experiments with LOFAR, where we can have many more (sub-)stations. So 
> far I have not run in the limit, but it can easily happen. Maybe go for 100 
> (99 plus centre of Earth)?
>
> I am aware of one more limit that I once reached:
>
> # MAX_ARC_SRC=300   in cmxsr11.i
>
> I used a field of many sources to test how good some polynomial (as function 
> of position) approximation was. 300 is probably good enough for almost all 
> purposes, just want to mention it for completeness.
>
>
> Cheers,
> Olaf
>
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-- 
-------------------------
Walter Brisken
Director
Long Baseline Observatory
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