APSR: digital signal processing at Parkes Willem van Straten, Andrew Jameson and Matthew Bailes Centre for Astrophysics & Supercomputing Third ATNF Gravitational Wave Workshop 2009

ATNF Parkes Swinburne Recorder Combination of FPGAs and CPUs  PDFB3 implements polyphase filterbank  16 processing nodes receive sub-band as UDP stream Real-time and/or offline data reduction  record data to disk at 1.6 GB/s for 2.5 hours Remote control and monitoring  web-based interface

Parkes Digital Filterbank Designed/developed at ATNF  2 x Compact Array Broad-band (CABB) board  up to 2048 channel polyphase filterbank  real-time RFI mitigation CABB = 2GHz correlator  modularity of FPGA design  hardware re-use

APSR Features Phase-coherent dispersion removal (up to 1024 MHz) Automatic impulsive interference excision  RFI, lightning, etc. Single-pulse capability  with real-time calibration and/or giant pulse selection Fold multiple pulsars simultaneously  globular clusters, binary pulsar Computation of auxiliary statistics  e.g. fourth-order moments

Phase-coherent dispersion removal Observed voltage signal is deconvolved  impulse response function of ISM plasma dispersion Convolution performed in frequency domain  more efficient, requires FFT N fft proportional to DM  2 / 3

Phase-coherent dispersion removal flops = 5NlogN / t FFT on each APSR node: (assuming DM=10) centre frequency bandwidth per node optimal N fft required Gflops 3.1 GHz64 MHz128k GHz16 MHz128k MHz4 MHz64k0.7

FFT benchmarks 700 MHz 1.4 GHz 3.1 GHz

Multi-threaded dspsr thread-safe revisions to underlying library thread-shared buffering of overlap regions  overlap-save method of discrete convolution thread-coordinated output of results  threads combine results every 10 seconds near linear scaling of performance!

Coherent Dedispersion - History Arecibo  XDS Sigma 5 magnetic tape  20% duty cycle for 3 minutes MHz  Reticon R5601 chip  real-time! Parkes  S2, VHS tape Parkes  CPSR, DLT tape MHz  CPSR2, high-speed disk MHz  APSR, real-time

XDS Sigma 5: picture

XDS Sigma 5 vs iPod

APSR web-based interface

: DFB3

: APSR

CAL lightning: DFB3

CAL lightning: APSR

Single pulse

Average pulse

Testing & Commissioning Polarimetric Calibration High-precision timing Frequency response tests User and TCS interface improvements GOAL: National Facility Instrument