The DiFX Software Correlator at IRA R I IRA-INAF /

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Contents 1 Introduction 5 1.1 Aims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2 Overview of the Correlation Process 8 2.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Broadband Data . . . . . . . . . . . . . . . . . . . . . 9 2.1.2 Vex Files . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.3 Earth Orientation Parameters (EOPs) . . . . . . . . . 10 2.1.4 Antenna log files . . . . . . . . . . . . . . . . . . . . . 10 2.1.5 Clock Offsets and Rates . . . . . . . . . . . . . . . . . 10 2.1.6 Correlation Parameters . . . . . . . . . . . . . . . . . 11 2.2 Geometric Modelling . . . . . . . . . . . . . . . . . . . . . . . 11 2.3 Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4 Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4.1 FITS-IDI . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3 The Software Correlator and Related Software 14 3.1 The Software Correlator . . . . . . . . . . . . . . . . . . . . . 14 3.2 Geometry Modelling Software . . . . . . . . . . . . . . . . . 14 3.3 NRAO-DiFX . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.4 vex2difx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.5 IRA-DiFX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4 Chosen Third-party Software in Detail 16 4.1 mpifxcorr (DiFX) . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.1.1 External Libraries . . . . . . . . . . . . . . . . . . . . . 16 4.1.2 Structure of DiFX . . . . . . . . . . . . . . . . . . . . . 17 4.2 vex2config.pl (vex2difx) . . . . . . . . . . . . . . . . . . . . 18 4.3 calcif (NRAO-DiFX) . . . . . . . . . . . . . . . . . . . . . . 18 4.4 difx2fits (NRAO-DiFX) . . . . . . . . . . . . . . . . . . . . 18 2
5 IRA-DiFX Software in Detail 20 5.1 Vex parsers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.1.1 vex2calc.py . . . . . . . . . . . . . . . . . . . . . . . . 20 5.1.2 vex2flag.py . . . . . . . . . . . . . . . . . . . . . . . . 20 5.2 Log parsers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.2.1 log2input.py . . . . . . . . . . . . . . . . . . . . . . . 21 5.2.2 log2tsys.py . . . . . . . . . . . . . . . . . . . . . . . . 21 5.2.3 log2comment.py . . . . . . . . . . . . . . . . . . . . . . 21 5.3 Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.3.1 machinegen.py . . . . . . . . . . . . . . . . . . . . . . 22 5.3.2 killdifx.py . . . . . . . . . . . . . . . . . . . . . . . . 22 5.4 Wrappers for 3rd-party Programs . . . . . . . . . . . . . . . 22 5.4.1 calcif.py . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.4.2 difx2fits.py . . . . . . . . . . . . . . . . . . . . . . . 22 5.4.3 mpifxcorr.py . . . . . . . . . . . . . . . . . . . . . . . 23 5.5 Integration of the various tools . . . . . . . . . . . . . . . . . 23 5.5.1 correlator_defaults.py and observation.py . . . 23 5.5.2 pydifx.py . . . . . . . . . . . . . . . . . . . . . . . . . 23 6 The Computer Cluster Used for Correlation 24 6.1 Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.2 File Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.3 Benchmarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.3.1 Bottlenecks . . . . . . . . . . . . . . . . . . . . . . . . 25 6.4 Other Software . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7 Correlation: Step by Step 26 7.1 Preparing the Input Files . . . . . . . . . . . . . . . . . . . . 26 7.2 Geometric Modelling . . . . . . . . . . . . . . . . . . . . . . . 27 7.3 Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.4 Conversion and Post-processing . . . . . . . . . . . . . . . . 27 8 Upgrade Path 28 8.1 Next Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.1.1 Other Changes . . . . . . . . . . . . . . . . . . . . . . 29 8.1.2 Development Branch . . . . . . . . . . . . . . . . . . . 30 8.1.3 Our Contribution . . . . . . . . . . . . . . . . . . . . . 30 A Detailed Notes on Correlation: Step by Step 32 A.1 Preparing the Input Files . . . . . . . . . . . . . . . . . . . . 32 A.2 Geometric Modelling . . . . . . . . . . . . . . . . . . . . . . . 34 A.3 Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 A.4 Conversion and Post-processing . . . . . . . . . . . . . . . . 35 3
Page 1: The DiFX Software Correlator at IRA
Page 5 and 6: Chapter 1 Introduction This report
Page 7 and 8: 1.2 Conventions In this document:
Page 9 and 10: 2.1 Inputs 2.1.1 Broadband Data The
Page 11 and 12: 2.1.6 Correlation Parameters There
Page 13 and 14: Other Log files may also include we
Page 15 and 16: 3.3 NRAO-DiFX The aim of the NRAO-D
Page 17 and 18: Intel R○ Integrated Performance P
Page 19 and 20: 19 Table 4.1: Overview of the Corre
Page 21 and 22: nonsense data between the scans. Th
Page 23 and 24: 5.4.3 mpifxcorr.py mpifxcorr.py run
Page 25 and 26: 6.2 File Systems The input data is
Page 27 and 28: 7.2 Geometric Modelling 1. Run calc
Page 29 and 30: prove useful for wide-field VLBI im
Page 31 and 32: Acknowledgements Many thanks to Fra
Page 33 and 34: Edit the .input file by hand - Set
Page 35 and 36: # ls -rt ... example.delay example.
Page 37 and 38: Appendix B Instructions on Installa
Page 39 and 40: for i in range(1, nscans): c.set_in
Page 41 and 42: [11] O. J. Sovers, J. L. Fanselow,

The DiFX Software Correlator at IRA R I IRA-INAF /

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