[Difx-users] Debugging a Nightmare problem

[Adam Deller]

Hi Richard,

Looks like there is a problem mid-file, and when it tries to re-sync the
header it finds is corrupted.  I can suggest a couple of things to try:

you can run countVDIFpackets (a utility in vdifio) which is probably slower
than vdifsummary (what utility is this?  I'm not aware of a "vdifsummary",
there is a "vsum"...?) and is pretty basic but actually does check for
every packet, and prints a message every time a problem is seen.  That
might give you some extra clues, so I'd try that first.  And if you really
want to get blasted away by lots of logging, you can use printVDIF, which
prints a little summary of each and every packet header.  You could pipe
that to grep to look for anomalies.

Looks like the problem is very early in the file, so if you dd the first
second or so and put it on an ftp server somewhere, I could also take a
look.

Cheers,
Adam

On Mon, Aug 22, 2016 at 10:57 AM, Richard Dodson <richard.dodson at uwa.edu.au>
wrote:

> Dear All
>
>  I have one of the usual nightmare twisted DiFX correlation problems.
>
>  I am trying to use DiFX on VDIF data which has been copied off the VERA
> OCTAVE systems (and similar) and converted.
>
>   The problem is almost certainly in the data copying -- but I need to
> provide some feedback on what is wrong for it to be fixed
>
>   The first problem that I found was in the VDIF file: all the invalid
> flags were set, the number of channels was wrong and the date was wrong by
> 1 day. :(
>
>   Jan has a program to fix all of these :) -- but he is not around to
> check if I have used this correctly :( :(
>
>    After these fixes the correlation runs, but the data file is empty.
> What messages should I be checking to work out what is happening? I append
> some messages which look suspicious but don't convey any information to me
> ...
>
>         All the best
>             Richard
>
> Comments:
>   vdifsummary reports seem OK
>
> # vdifsummary /lustre/kjcc/k16mk02f/MIZ/k16mk02f_kava_miz.vdif
> [1:1] check k16mk02f_kava_miz.vdif -> Good! it is a VDIF data scan -> add
> to 1
> k16mk02f_kava_miz.vdif   4,108,790,400,000   31317 sec( 8:41:57)   57467
> Mar 20 2016y080d 11:00:03 - 19:41:59  1312 100000
> 3,827 GB(=  3.7 TB)(= 4,108,790,400,000 B)
>
> Log messages which might be relevant:
>
> 2016-08-22 16:30:32,548 DiFXAlert INFO    MPI[ 1] compute-0-28.local
> k16mk02f_1   Datastream 1 has opened file index 0, which was
> /lustre/kjcc/k16mk02f/MIZ/k16mk02f_kava_miz.vdif
>
> 2016-08-22 16:30:32,548 DiFXAlert VERBOSE MPI[ 2] compute-0-28.local
> k16mk02f_1   input.bad() is 0, input.fail() is 0
>
> 2016-08-22 16:30:32,700 DiFXAlert ERROR   MPI[ 1] compute-0-28.local
> k16mk02f_1   Lost Sync on segment 1! Will attempt to resync. Deltatime was
> -1.13239e+09
>
> 2016-08-22 16:30:32,701 DiFXAlert INFO    MPI[ 1] compute-0-28.local
> k16mk02f_1   Config has changed!
>
> 2016-08-22 16:30:32,702 DiFXAlert INFO    MPI[ 1] compute-0-28.local
> k16mk02f_1   After regaining sync, the frame start day is 70573, the frame
> start seconds is 70631, the frame start ns is -2147483648, readscan is 2,
> readseconds is 1132388471, readnanoseconds is -2147483648
>         note the 2^31 values !!!!
>
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>


-- 
!=============================================================!
Dr. Adam Deller
Ph  +31 521595785 / Fax +31 521595101
Staff Astronomer, Astronomy Group
ASTRON, Oude Hoogeveensedijk 4
7991 PD Dwingeloo, The Netherlands
!=============================================================!
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