Cobalt: A GPU-based correlator and beamformer for LOFAR

Abstract

For low-frequency radio astronomy, software correlation and beamforming on general purpose hardware is a viable alternative to custom designed hardware. LOFAR, a new-generation radio telescope centered in the Netherlands with international stations in Germany, France, Ireland, Latvia, Poland, Sweden and the UK, has successfully used software real-time processors based on IBM Blue Gene technology since 2004. Since then, developments in technology have allowed us to build a system based on commercial off-the-shelf components that combines the same capabilities with lower operational cost. In this paper we describe the design and implementation of a GPU-based correlator and beamformer with the same capabilities as the Blue Gene based systems. We focus on the design approach taken, and show the challenges faced in selecting an appropriate system. The design, implementation and verification of the software system shows the value of a modern test-driven development approach. Operational experience, based on three years of operations, demonstrates that a general purpose system is a good alternative to the previous supercomputer-based system or custom-designed hardware.

References in corpus (9)

• LOFAR: The LOw-Frequency ARray
• DiFX2: A more flexible, efficient, robust and powerful software correlator
• The Precision Array for Probing the Epoch of Reionization: 8 Station Results
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• The SFXC software correlator for Very Long Baseline Interferometry: Algorithms and Implementation
• The LOFAR Pilot Surveys for Pulsars and Fast Radio Transients
• A real-time software backend for the GMRT
• The Murchison Widefield Array Correlator
• Correlating Radio Astronomy Signals with Many-Core Hardware

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• LOFAR Detection of 110-188 MHz Emission and Frequency-Dependent Activity from FRB 20180916B
• The LOFAR Tied-Array All-Sky Survey (LOTAAS): Survey overview and initial pulsar discoveries
• Unintended electromagnetic radiation from Starlink satellites detected with LOFAR between 110 and 188 MHz
• First upper limits on the 21 cm signal power spectrum from cosmic dawn from one night of observations with NenuFAR
• Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition
• Long Term Variability of a Black Widow's Eclipses -- A Decade of PSR J2051$-$0827
• Multi-frequency observations of SGR J1935+2154
• Deep Learning Assisted Data Inspection for Radio Astronomy
• Imaging of the Quiet Sun in the Frequency Range of 20-80 MHz
• Searching for pulsars associated with polarised point sources using LOFAR: Initial discoveries from the TULIPP project
• The ROAD to discovery: machine learning-driven anomaly detection in radio astronomy spectrograms
• First Results from the REAL-time Transient Acquisition backend (REALTA) at the Irish LOFAR station
• MWAX: A New Correlator for the Murchison Widefield Array
• LOFAR Measures the Hotspot Advance Speed of the High-Redshift Blazar S5 0836+710
• MWA Tied-Array Processing IV: A Multi-Pixel Beamformer for Pulsar Surveys and Ionospheric Corrected Localisation
• Pipeline Collector: gathering performance data for distributed astronomical pipelines
• Real-time stream processing in radio astronomy
• Tied-array holography with LOFAR
• On optimising cost and value in compute systems for radio astronomy
• Efficient channelization on a Graphics Processing Unit