mwatelescope / mwax_db2fits

MWA Correlator (mwax) PSRDADA ringbuffer datablock to FITS file

mwax-db2fits

MWA Correlator (mwax): PSRDADA ringbuffer to FITS file converter

Dependencies

CFITSIO

• See https://heasarc.gsfc.nasa.gov/fitsio/fitsio.html

psrdada prerequisites

• pkg-config
• libhwloc-dev (this is to enable the use of NUMA awareness in psrdada)
• csh
• autoconf
• libtool

psrdada (http://psrdada.sourceforge.net/)

• download the source from the cvs repo (http://psrdada.sourceforge.net/current/)
• build (http://psrdada.sourceforge.net/current/build.shtml)

Building Release version

./build.sh

Running / Command line Arguments

Example from mwax_db2fits --help

mwax_db2fits v0.10.3

Usage: mwax_db2fits [OPTION]...

This code will open the dada ringbuffer containing raw
visibility data from the MWAX Correlator.
It will then write out a fits file to be picked up by the
archiver process.

  -k --key=KEY                      Hexadecimal shared memory key
  -d --destination-path=PATH        Destination path for gpubox files
  -n --health-netiface=INTERFACE    Health UDP network interface to send with
  -i --health-ip=IP                 Health UDP Multicast destination ip address
  -p --health-port=PORT             Health UDP Multicast destination port
  -l --file-size-limit=BYTES        FITS file size limit before splitting into a new file. Default=10737418240 bytes. 0=no splitting
  -v --version                      Display version number
  -? --help                         This help text

Testing an Debugging

Build the Debug Binary

./build_debug.sh

Run all tests

./run_tests.sh

Health Packet format

Every 1 second, a UDP health packet is sent to the health_ip and health_port via the health-netiface interface.

The payload is a packed C struct with the following format:

Type	Name	Example	Notes
int16	version_major	1	mwax_db2fits major version number
int16	version_minor	2	mwax_db2fits minor version number
int16	version_revision	3	mwax_db2fits revision number
char[64]	hostname	mwax01	hostanme of the server
time_t	start_time	1683779031	UNIX Time when program was started
time_t	health_time	1683780123	UNIX Time when health packet was assembled
float64	up_time	1092	Number of seconds alive
int16	status	1	0 = Offline, 1= Running, 2= shutting down
int32	obs_id	1234567890	obs_id GPS time or 0 if no current observation
int32	subobs_id	1234567890	sub_obs_id GPS time or 0 if no current observation
float32[256]	weights_per_tile_x	1.0,0.9,0.92,1.0...	Each element is tile 0..255 X pol weight. If ntiles is <256, unused tiles will have NaN. If no weights can be reported then the array will have 256 NaN elements. Tile order is MWAX order.
float32[256]	weights_per_tile_y	1.0,0.9,0.92,1.0...	Each element is tile 0..255 Y pol weight. If ntiles is <256, unused tiles will have NaN. If no weights can be reported then the array will have 256 NaN elements. Tile order is MWAX oder.

mwax_db2fits's Issues

Build fits file with a temp filename then rename only when fully complete and good

This should prevent accidently archiving incomplete or broken fits files caused by the correlator processes crashing or restarting.

Maybe also clean up any temp files upon startup too.

Detect low disk space

Instead of leaving a partial fits file, do not write a file unless there is enough disk space available

Handle interrupted observations better

For each new 8 sec sub obs, compare the PSRDADA header durtation with the metafits duration. If a trigger has interrupted this obs, then the metafits will have either

1. a different (shorter) duration. Use that instead of the PSRDADA header and thus, finish and close off the current FITS file so we can start the new one.
   OR
2. it will be a totally different obsid than what I was expecting (and subobsid will == obsid) in which case, just close off the FITS file I currently had and start this new FITS file.

Send summary weights info in the health packets

Average weight per tile per pol per 1 second to be included in health packets.
Presumably it will be in the form of:

• 1 float per tile per pol (x,y)

Provide uptime in health data

Remove any extraneous keywords from the fits files produced

Example: ProjectID - this metadata is not necessary in the data files since we have the obs_id.

Add cmd line to health packets

mwax auto correlation stats filenames

Generate 1 file per sub obs as currently do, but the filename should be based on the last 2 digits of the gps second, and just continuously overwrite.

Shape of data should be based on ninputs, not ninputs_xgpu

The correlator works in 16 rfinput chunks, so if we have a 129 tile observation, there will be 258 rfinputs. xgpu will produce data out of the correlator of shape 288 rfinputs (with the extra ones just padded with 0s). The correlator, however already trims these extraneous rfinputs, so mwax_db2fits only needs to care about the ninputs value not the ninputs_xgpu value.

When subobsid jumps in time by >8 seconds, discard obs and wait for a new one- do not abort