Development of DiFXAdam Deller

NRAO

3rd DiFX workshop, Curtin University, Perth

Adam Deller 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

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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

QuickTime™ and a decompressor

are needed to see this picture.

The S2 correlator

Adam Deller 3rd DiFX workshop, Curtin University, Perth

DiFX: the raison d’etre

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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??

Adam Deller 3rd DiFX workshop, Curtin University, Perth

Science highlights at the LBA First trans-Tasman fringes - to a 6m dish in

NZ!

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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

Adam Deller 3rd DiFX workshop, Curtin University, Perth

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!