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Development of DiFX

Development of DiFX. Adam Deller NRAO 3rd DiFX workshop, Curtin University, Perth. Outline. Reasons for the development of DiFX Development of fxcorr (pre-DiFX) Rationale and planning of DiFX DiFX for the LBA DiFX at NRAO and elsewhere. DiFX: the raison d’etre.

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Development of DiFX

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  1. Development of DiFX Adam Deller NRAO 3rd DiFX workshop, Curtin University, Perth

  2. Outline • Reasons for the development of DiFX • Development of fxcorr (pre-DiFX) • Rationale and planning of DiFX • DiFX for the LBA • DiFX at NRAO and elsewhere 3rd DiFX workshop, Curtin University, Perth

  3. DiFX: the raison d’etre • In 2004, the LBA installed new disk-based recorders capable of 4x the bandwidth of the S2 tape system • The existing hardware correlator could not interface to the new recorders • Required: a “stop-gap” solution before the CABB correlator for ATCA was ready for VLBI data The S2 correlator 3rd DiFX workshop, Curtin University, Perth

  4. DiFX: the raison d’etre 3rd DiFX workshop, Curtin University, Perth

  5. 2005: Development of fxcorr • My PhD began February 2005 - first attempt was FX-style correlator which ran on a single node (distribution via scripts/data division) • Naivete in both C++ and correlators led me to build in some idiosyncracies/inefficiencies • Verified against S2 results, but plans made to redesign from scratch, using data distribution with MPI - mpifxcorr, copy/pasting the internals of the correlation code 3rd DiFX workshop, Curtin University, Perth

  6. Rationale/planning of DiFX • At this stage, plans made to support other formats than LBA (specifically Mark5) • Attempted to not “design out” any general applications, but the main focus was nevertheless on LBA operations • Also made provisions from the outset for eVLBI connections into the correlator • Main development was complete by mid 2006 3rd DiFX workshop, Curtin University, Perth

  7. DiFX at the LBA • DiFX has been the production correlator of the LBA since end of 2006 • Plans to use the CABB correlator as the LBA correlator have been shelved • 2008: Correlation moves from Swinburne to Curtin • Oversubscription rate has risen substantially since DiFX + LBADR (recorders) introduced - maybe ~1.5 to ~3?? 3rd DiFX workshop, Curtin University, Perth

  8. Science highlights at the LBA • First trans-Tasman fringes - to a 6m dish in NZ! 3rd DiFX workshop, Curtin University, Perth

  9. Science highlights at the LBA • First trans-Tasman fringes - to a 6m dish in NZ! • First southern hemisphere eVLBI, detecting a flare in Circinus X1 3rd DiFX workshop, Curtin University, Perth

  10. Science highlights at the LBA • First trans-Tasman fringes - to a 6m dish in NZ! • First southern hemisphere eVLBI, detecting a flare in Circinus X1 • 6 new pulsar parallaxes, trebling the number of Southern pulsar parallaxes 3rd DiFX workshop, Curtin University, Perth

  11. DiFX at the VLBA • VLBA sensitivity upgrade has been an ongoing project that requires a new correlator to deal with increased data rates • DiFX selected in 2008 • Going “live” this proposal cycle - first element of the upgrade (backends and recorders to come) to do so • Huge amounts of streamlining and infrastructure have been contributed by the NRAO efforts 3rd DiFX workshop, Curtin University, Perth

  12. DiFX worldwide • DiFX is likely to replace three other existing hardware correlators: Bonn, USNO, Haystack • This is the third DiFX workshop - attendance has gone from about 8 to about 12 to about 24 - the last year especially has been an exciting time development- and adoption-wise • Lets keep this thing rolling! 3rd DiFX workshop, Curtin University, Perth

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