@@ -205,7 +205,7 @@ The beamformer creates the beams as described in Section \ref{Sec:Beamforming}.
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@@ -205,7 +205,7 @@ The beamformer creates the beams as described in Section \ref{Sec:Beamforming}.
The delays are applied to the station data through complex multiplications and additions, programmed in assembly. In order to take full advantage of the L1 cache and the available registers, data is processed in sets of 6 stations, producing 3 beams, or a subset thereof to cover the remaining stations and beams. While the exact ideal set size in which the data is to be processed depends on the architecture at hand, we have shown in previous work that similar tradeoffs exist for similar problems across different architectures~\cite{Nieuwpoort:09,BAR}.
The delays are applied to the station data through complex multiplications and additions, programmed in assembly. In order to take full advantage of the L1 cache and the available registers, data is processed in sets of 6 stations, producing 3 beams, or a subset thereof to cover the remaining stations and beams. While the exact ideal set size in which the data is to be processed depends on the architecture at hand, we have shown in previous work that similar tradeoffs exist for similar problems across different architectures~\cite{Nieuwpoort:09,BAR}.
Because each beam is an accumulated combination of the data from all stations, the bandwidth of each beam is equal to the bandwidth of data from a single station, which is 6.2~Gb/s now that the samples are 32-bit floating point numbers. Once the beams are formed, they are kept as XY polarisations or transformed into the Stokes IQUV or the Stokes I parameters. In the latter case, the beams can also be integrated time-wise, in which groups of samples of fixed size are accumulated together to reduce the resulting data rate.
Because each beam is an accumulation of the data from all stations, the bandwidth of each beam is equal to the bandwidth of data from a single station, which is 6.2~Gb/s now that the samples are 32-bit floating point numbers. Once the beams are formed, they are kept as XY polarisations or transformed into the Stokes IQUV or the Stokes I parameters. In the latter case, the beams can also be integrated time-wise, in which groups of samples of fixed size are accumulated to reduce the resulting data rate.
The beamformer transforms chunks representing station data into chunks representing beam data. Because a chunk representing station data contained data for only one subband, the chunks representing different subbands of the same beam are still spread out over the full BG/P. Chunks corresponding to the same beam are brought together using a second all-to-all exchange.
The beamformer transforms chunks representing station data into chunks representing beam data. Because a chunk representing station data contained data for only one subband, the chunks representing different subbands of the same beam are still spread out over the full BG/P. Chunks corresponding to the same beam are brought together using a second all-to-all exchange.
