The CHIME Pathfinder is a new interferometric radio telescope that uses ahybrid FPGA/GPU FX correlator. The GPU-based X-engine of this correlatorprocesses over 819 Gb/s of 4+4-bit complex astronomical data from N=256 inputsacross a 400 MHz radio band. A software framework is presented to manage thisreal-time data flow, which allows each of 16 processing servers to handle 51.2Gb/s of astronomical data, plus 8 Gb/s of ancillary data. Each server receivesdata in the form of UDP packets from an FPGA F-engine over the eight 10 GbElinks, combines data from these packets into large (32MB-256MB) bufferedframes, and transfers them to multiple GPU co-processors for correlation. Theresults from the GPUs are combined and normalized, then transmitted to acollection server, where they are merged into a single file. Aggressiveoptimizations enable each server to handle this high rate of data; allowing theefficient correlation of 25 MHz of radio bandwidth per server. The solutionscales well to larger values of N by adding additional servers.
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