[daip] CPASS bug

[Leonia Kogan]

Hi Kristine,

>In particular, I am trying to calibrate the bandpass of a
>dataset for which the two central channels are corrupt,

If the same frequency channels are corrupted for all your data 
then you have to get rid of these channels (task AVSPC, UVFLG ...)...

So tell me whether it is the case.

Send me please the list of the input parameters you used for CBAND

Leonia



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Subject: [daip] CPASS bug
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Date: Tue, 6 Aug 2002 13:02:53 -0400 (EDT)
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Hello,

 My name is Kristine Spekkens; I am a graduate student at Cornell
University.  I am reducing VLA spectral line data at L-band with AIPS
(31DEC02).  In particular, I am trying to calibrate the bandpass of a
dataset for which the two central channels are corrupt, but the rest of
the channels (~60 of them) make a very stable, almost linear bandpass.
So, I figured I would try to fit a polynomial solution to the "good"
calibrator data with CPASS.

 When I execute the task (with a message level of 2), however, it appears
to begin finding polynomial solutions, but then prints

>NIT  NF       F              GTG

ad infinitum until I abort it.  The format declaration for this output is
found on line 3873 of the source code CPASS.FOR, followed by a declaration
of variables apparently corresponding those values:
800 FORMAT(' NIT NF',9X, 'F', 21X, 'GTG')
810 FORMAT(' ',I3,1X,I4,1X,1PD22.15,2X,1PD15.8)

These declarations are used to print messages to the user starting on line
3651; it seems as though the message I am getting should only be printed
once, as a header to the information which follows (about each iteration
of the bandpass solution).  That bit of the code reads:

C
C INITIALIZE PARAMETERS AND CONSTANTS
C
      IF (MSGLVL .GE. 1) THEN
         WRITE(MSGTXT,800)
         CALL MSGWRT (3)
         END IF
C
      CALL SETPAR(N)
      UPD1 = .TRUE.
      IRESET = 0
      NFEVAL = 0
      NMODIF = 0
      NLINCG = 0
      FSTOP = F
      ZERO = 0.D0
      ONE = 1.D0
      NM1 = N - 1
C
C WITHIN THIS ROUTINE THE ARRAY W(LOLDG) IS SHARED BY W(LHYR)
C
      LHYR = LOLDG
C
C CHECK PARAMETERS AND SET CONSTANTS
C
      CALL CHKUCP(LWTEST,MAXFUN,NWHY,N,ALPHA,EPSMCH,
     *     ETA,PEPS,RTEPS,RTOL,RTOLSQ,STEPMX,FTEST,
     *     XTOL,XNORM,X,LW,SMALL,TINY,ACCRCY)
      IF (NWHY .LT. 0) GO TO 120
      CALL SETUCR(SMALL,NFTOTL,NITER,N,F,FNEW,
     *     FM,GTG,OLDF,SFUN,G,X)
      FOLD = FNEW
      IF (MSGLVL .GE. 1) THEN
         WRITE(MSGTXT,810) NITER,NFTOTL,FNEW,GTG
         CALL MSGWRT (3)
         END IF

 So it seems that somewhere between the write at the top of this chunk
{WRITE(MSGTXT,800)} and the one at the bottom {WRITE(MSGTXT,810)
NITER,NFTOTL,FNEW,GTG}, the program is getting caught in an infinite loop
which causes repeated printing of the header.

 I'd be happy to provide the inputs to CPASS that I used if you think that
it would help.

 Thanks,

Kristine


----------------------------------------------------
Kristine Spekkens
Graduate Student, Department of Astronomy
Cornell University, Ithaca NY 14853
spekkens at astro.cornell.edu
----------------------------------------------------

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