[daip] FRING problem in NEW and TST

[Eric Greisen]

Walter Alef wrote:
> Hi Eric,
> 
> We encountered a problem with FRING in the TST and NEW version. OLD is not 
> affected. We think that the problem was introduced after about summer 2010. 
> We saw this with data with single and full polarisation.
> 
> The found the problem when we set up FRING for determining manual phase-cals 
> which means fringe fitting 2 mins of data with aparm(5)=0 and dparm(8)=1 
> We see that the fits in the FFT step look reasonable (low residuals), they 
> close as I verified by hand, but in the LSQ step occasionally extreme delays 
> and phases show up which totally disagree from the results of the FFT step. 
> Typically some of the higher IFs of some stations are affected, visible in a 
> POSSM plot as strong phase slope in the affected IFs/antennas.
> One of the datasets for which we found this can be found under 
> ftp://ftp.mpifr-bonn.mpg.de/vlbiarchive/correlator/c101a_077.fits (is a bit 
> big I am afraid)
> 
> I hope this is all the info you need. Otherwise please tell me what else you 
> need.

I loaded your data onto my computer which runs LNX64 and on another 
computer which runs LINUX (as in Bonn).  I then ran 3 versions of FRING.
On mine they were TST (GNU), CVX (Intel 64), and OLD (GNU).  On the 
LINUX one, they were TST (as at Bonn), my debug one (GNU), and OLD (as 
at Bonn).  To a large extent the 6 SN tables were identical.  There is 
one difference in that OLD gets an extra record due to mishandling scan 
boundaries.  The solution at that time is still quite reasonable.

I have not looked at the detailed set of messages that appeared, just 
run SNPLT for 'DELA'.  Is there something I am missing?

Eric Greisen