VEGAS Pulsar Project Meeting: 2015 December 14th 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

Agenda

BOF file status updates

• c1500x4096 mode
  • Recompiled GPU transpose code
  • nVidia profiling
    • No update
  • guppi_daq_server version comparisons
    • No update
• c1500x0512 mode
  • Build status
    • Built successfully
  • Simulator tests
    • Bandpass looks good and stable except for low-level feature in channel 48

• • • Scans failing during long integrations
      • Update status shared memory code to use different data type to accurately capture packet ID
  • Astronomical verification
    • No update
• c1500x2048 mode
• Fix for nchan calculation in coherent modes
  • Ready to implemented in other modes
• Bandpass issues in i0800x0064, 0128, 8192
  • Spent some time testing 64 channel mode
  • Tone shows up in the correct bins, but generates spurs if injected at Fs/8 or nearby
    • Spurs move with the test tone and decrease with amplitude if you move away from Fs/8
    • May be problem with MMCM or OGP calibration
      • Will try to check with real VEGAS hardware on Thursday afternoon
      • Justin will talk with Paul M about MMCM and OGP calibration
      • All snapblocks with correct names are present
• Duplicated signal in i0800x8192
• Low bandwidth modes
  
  • New filter coefficients
  • Spectrum output instead of time series
  • Implement PFB code
  • Could single GPU keep up with coherent dedispersion?

Software

• Configtool changes
  
  • First tests carried out with GBT
    • Status of vegas.polarizationmode and vegas.fold_dumptime parameters
  • Status of rebasing on current release version
• GBT Status shared memory parameters in PSRFITS headers
  • Set observer and source and check PSRFITS headers
  • Verify with GBT hardware
• Switching signal generation
  • Subset met Friday to discuss how to proceed
  • It was realized that the current packet formats in pulsar modes do not allow for sending information about blanking state and that spectral-line approach to switching with VEGAS is not possible without significant modifications
  • We decided that VEGAS should replicate the behavior of the DCR as it is used with GUPPI, which requires only switching the noise diode at the appropriate rate
    • Decided not to use DCR itself so as not to tie VEGAS pulsar modes into the fate of another instrument
  • Modifications will require a new register to control switching in pulsar modes, but it should be very simple
    • Does require describing the switching duration with 27-bits
  • Software modifications should be simple as there will be no need to calculate values such as spectick and to determine how they relate to granularity of blanking time and switching period
  • Ray believes we can switch at the requested rate (0.04 s is standard) with 0.9 ns accuracy, which is more than enough for pulsar calibration scans
    • What is this number based on?
• Matrix HPC
  • Any outstanding questions regarding difference between search and baseband packets?
    • Will different modes use the same net thread in the Matrix?
    • Any issue with overlapping in coherent modes?

GBT testing

• TBD

Wideband AP

• Status of new filters

VEGAS/DIBAS-style backend for FAST

• Karen gave her approval to send to Tony Beasley
• Any other updates?

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

Resource Allocations for next quarter

Date / Time of Next Meeting

• TBD