[daip] clean component filtering

[Eric Greisen]

Andy Biggs wrote:
> Hi there. I'm having a difficult time at the moment with some map 
> making. I have a lot of maps to make and I want to do it in as 
> *automated* a fashion as possible. I am doing a wide-field deep clean at 
> 21cm and am using a fly's-eye faceting approach. The problem is that 
> some of the facets do not contain any sources which results in them 
> ending up with lots of weak, spurious clean components which I want to 
> exclude from CALIB (this is before each epoch is combined together with 
> STUFFR).
> 
> My favoured way of dealing with this would be to run CCEDT. However, it 
> seems that in those fields where all the clean components would be 
> (correctly) rejected, CCEDT doesn't do what I would like it to, and 
> which I think it should, which is to write out a new *empty* CC table.
> 
I have changed CCEDT to allow writing an empty CC file with a warning 
message but not an error condition.

> I've tried various other approaches, such as flagging the entries using 
> TAFLG, but that caused CALIB to do some very strange things, mainly only 
> using a small and somewhat random number of the many fields. I've tried 

The new code that attempts to do many facets at once (to reduce reading 
the data set) still had an old error branch for 0 components in a facet.
I have changed it to branch only on 0 components in all facets of a group.
> running IMAGR with the filtering option (IMAGRPRM(8,9)) but this didn't 
> seem to do anything at all i.e. IMAGR didn't even begin (nothing 
> appeared in the MSGSRV and no activity was reported by 'top'). One thing 
> that sort of worked was to set field cards as 'F -1 -1 0 0' in BOXFILE 
> which prevented IMAGR placing a box in that field. However, you then 
> need to tell IMAGR the size of the field through IMSIZE and you can only 
> do this once i.e. if you have different sized fields (which I do) you 
> can't really do this. Also, you need to know in advance which fields 
> aren't going to have any sources.
> 
If you do know what facets are empty, IMAGR will now allow you to enter 
a BOXFILE line
nnnn 0 0 0 0
to say that facet nnn has no Clean boxes to start with.

Eric Greisen