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Whereas the legacy correlator utilizes a polyphase filterbank for the F-engine, the MWAX correlator employs the FFT. For the X-engine, development time/cost has been minimized by utilizing the existing open-source GPU correlator library “xGPU” (the same library at the heart of the legacy correlator). The standard xGPU library is used essentially unchanged for MWAX, with the exception of a small but crucial change to improve speed and reduce bus/memory traffic, found to be essential to making the design scalable to 256T and beyond. This modification is described in Appendix C.
The 24 coarse channels are processed by 24 GPU-accelerated compute nodes referred to as “MWAX Servers”, with two ‘hot spares’. Each MWAX Server implements the functions shown in the figure below. The real-time data flows on the MWAX Servers are managed through the use of input and output ring buffers that decouple its computational workflow from the input source and output destinations. These ring buffers are established and accessed using the open-source standard library “PSRDADA”.
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