[Issues] AssociateList stores SIDs of one input SL as singles of the other SL

Hugo Buddelmeijer buddel at astro.rug.nl
Thu Dec 27 16:00:31 CET 2007

Hi all,

When creating an AssociateList, some sources are incorrectly stored as 
singles. The SIDs of the first input SourceList are stored as if they were 
singles of the second SourceList and vice-versa.

The problem exists both in the latest and in the AWBASE version. Below 
follows an illustration, and attached are a script to reproduce this and it's 

An example of a small area association illustrates this:
AssociateList 77681 is an association of SourceLists 183741 and 183751. The 
search_area is very small, so that both input SLs have only one source in 
that region:  10.65 < RA < 10.66,  -28.66 < DEC < -28.65

It is expected for the AssociateList to have only one association (AID), 
instead it has 3 (ra/dec/htm fetched with associates.get_data):

AID,   SLID, SID,    RA,    DEC,              HTM
   0, 183751, 590, 10.65, -28.64, 9133688156790416
   0, 183741, 752, 10.65, -28.64, 9133688156840465
   1, 183741, 590, 10.66, -28.69, 9133689464519126
   2, 183751, 752, 10.75, -28.58, 9133874796226817

Notice that each SID appears twice, once for both SLIDs. I.e. once in the 
correct association with AID=0 and once as a null-association. The sources 
belonging to the NULL-association are not within the search area of the
AssociateList. This is to be expected, because these combinations of SLID-SID 
are artificial bugs.

An afterthought: perhaps the SIDs are not stored as singles if the sources 
belonging to the spurious SLID-SID combinations were already matched. This 
happens in the `perfect' case when the two input SourceLists have the same 
amount of sources which are numbered consecutively.

And: Happy New year all :).


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