VEGAS Pulsar Project Meeting: 2016 March 21st 2:00 - 3:00pm ET

Room / Connection Details

• GB-137 / Soc 280
• 192.33.117.12##7144
• 434-817-6443

Housekeeping Details

• Main wiki page
• gbsapp Mailing List
• Location and regular date and time of meeting - agreed weekly on Mondays; GB-137 / Soc-280; 2-3pm ET
• ETK codes:
  • Electronics: 432510.GB3015
  • Software: 893252.GB3015
  • Science: 432540.GB3015

Resource Allocations

Present

• Randy, Jason, Justin, Marty, Ryan

Agenda

BOF file status updates

Coherent Modes

• Outstanding issues
  • Packet loss in c1500x4096 and c1500x2048 modes not unexpected. Action item: Talk to Dave McMahon in April about optimization for BL that we can pull in for VPM.
  • Packet loss in c1500x0128 mode is somewhat surprising, given that higher-channel modes seem to work well.
    • Ryan to talk with Joe/Randy about possible reasons for this on the guppi_daq side.
  • VEGAS samplers report that J2 IF input is receiving too much power in c0800x0256 and c0800x1024 modes. Manager reported problems with MMCM calibration that may be related. Action item:Justin and Ryan to look more closely at errors and talk to Paul M.
    • Jason and Randy did notice that there was variation of 5 (on a scale of -127 to 128) between two polarizations in some of the BOF file builds they were testing. Unsure of the root cause, but seems to be occurring in the ADCs. Action item: Jason to check which BOFs had this problem.

Incoherent Modes

• Outstanding Issues
  • i0800x0064 and i0800x0128 modes have incorrect bandpass shapes
    • Seem to have excess power in higher channels relative to lower channels
    • Injected tone is showing up at correct frequency
    • Spurs are seen at Fs/4 on both SRBS and VEGAS
    • OGM/MMCM calibration should be OK
  • i0800x2048 shows a duplicate pulsed signal, almost as if folding period is twice what it should be
  • i1500x8192 has problem in guppi_fold_thread
    • Error (guppi_fold_thread): Insufficient memory per block to hold fold results.
    • How much memory is available?
• Randy working on adding SS support and correct bandpass saturation behavior, will continue builds off parent version

Low bandwidth modes

• Current plan is to perform filterbank FFTs on GPU
  • Makes BOF file builds simpler
  • Requires CUDA development
  • Time series would be fed to HPC, which would perform PFB - corner turn - FFT - complex multiply - FFT - accumulate
    • Everything after corner turn exists in the coherent dedispersion algorithm
    • GPU code exists for PFB and corner turn in spectral line modes but needs to be merged with pulsar code

Software

• Coherent mode scans are failing to initialize in the simulator
  • Justin and Ray seemed isolated the problem to scans that are started by the Manager
    • They are able to manually configure and start scans (through Grail?) without issue
    • Possible timing problem?
    • Action item: Jason to double check that the SSDS on srbs isn't causing a problem.
    • Action item: Ryan to look at phase diagrams to see if SS is being set properly in simulator.
    • Action item: Jason also to look at dummy I2C module on srbs to make sure there isn't a problem there.
• Coordinator/Manager
  • Manager repeatedly prints a message regarding the IF Manager:

• This was related to changes in the ARGUS branch that were pulled into the VPM branch. This has been resolved.
• Configtool changes
  
  • Astrid still reports that VEGAS failed to balance when trying to adjust LBW gain. Still need to work on disabling this for pulsar modes.
  • Astrid still issues a warning about a discrepancy in the requested and actual IF rack power levels, though this did not cause a failure
    • This is because GUPPI and VEGAS have different power requirements. Dave Frayer suggested that VEGAS in wide bandwidth modes did not need to have it's targets set so high (currently 3 V). Could we use the same target (1 V) for GUPPI and VEGAS?
      • Action item: Ryan to talk to Galen. Justin can easily implement change with new values once these are decided on.
• Matrix HPC
• Low Bandwidth Modes

GBT testing

• Successfully tested several BOF files last week.
• Maintenance time is limited this week. Ryan to test spectral line modes and any new BOF files as they become available.
• If Config tool balance and Filter Rack power issues can be sorted out and spectral line modes look OK, Ryan will request motion tests for astronomical verification on a real pulsar.

Wideband AP

• Board is fully populated. Power supplies look good.
• Ready to start testing controle modules. Vereese has been working on FLAG so no progress on this yet.

VEGAS/DIBAS-style backend for FAST

• Work progressing as independent project
• NSF/AUI approved
• Contract sent to FAST. Second iteration of contract changes.

Multicasting for spectral line and pulsar modes

• Modifications to ROACH configuration and net task must bind to a multicast group instead of a specific host
  • All the 10-gig addresses on the ROACH would be multicast groups, and config will be told which to bind to
  • Some changes to net task code (in VEGAS HPC and guppi_daq code) to initialize sockets

Date / Time of Next Meeting

• April 4