[Difx-users] Debugging a Nightmare problem

[Richard Dodson]

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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