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Cotter4 can make use of 'Dysco' compression, which I'll describe briefly here. To make use of compression, Dysco needs to be separately installed, available at https://github.com/aroffringa/dysco . On Github you can also find some info on the Dysco Wiki and there's a paper describing the technique. Compression is only used when explicitly requested. The Dysco software is not needed when running Cotter without requesting compression. One can request compression by adding '-use-dysco' to the commandline. A run with default compression settings looks like:
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cotter4 -use-dysco -m 1077974936_metafits_ppds.fits -timeres 4 -freqres 80 *gpubox*.fits |
The advanced compression parameters can be set with a call like this:
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cotter4 -use-dysco -dysco-config 12 12 TruncatedGaussian 1.5 RF -m 1077974936_metafits_ppds.fits -timeres 4 -freqres 80 *gpubox*.fits |
This uses the following settings: use 12 bits per datafloat, 12 bits per weight float, optimize for a Gaussian distribution truncated at 1.5 sigma and use row-frequency normalization -- see cotter4 options & Dysco wiki for more info about these).
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