frbPostProcess

class frbPostProcess : public kotekan::Stage

Post-processing engine for data coming out of the CHIME/FRB kernel stack.

This engine gathers CHIME/FRB data from the 4 GPU streams in each CHIME node, packing it into CHIME/FRB L0-L1 packets, which are stored in the output buffer. Prior to packing, the (float) input values are scaled and offset to 8-bit unsigned ints (i.e., 0-255). The scaling is determined on a per-packet basis, using AVX2 instructions to calculate and apply those parameters.

This stage can also optionally produce a sum-of-all-beams “incoherent” beam, which will be stored in the 0th beam position in output packets.

Time samples with dropped packet are set to zero.

This stage depends on AVX2 intrinsics.

Buffers

• in_buf_0 Kotekan buffer feeding data from GPU0.

  • Format: Array of floats

  • Metadata: chimeMetadata

• in_buf_1 Kotekan buffer feeding data from GPU1.

  • Format: Array of floats

  • Metadata: chimeMetadata

• in_buf_2 Kotekan buffer feeding data from GPU2.

  • Format: Array of floats

  • Metadata: chimeMetadata

• in_buf_3 Kotekan buffer feeding data from GPU3.

  • Format: Array of floats

  • Metadata: chimeMetadata

• out_buf Kotekan buffer that will be populated with packetized data.

  • Format: Array of uchars

  • Metadata: chimeMetadata

• lost_samples_buf Koktekan buffer with drop packet info, where 1=dropped

  • Metadata: chimeMetadata

  • Format: Array of uint8

Metrics

• kotekan_frb_masked_packets_total Count of masked packets

Author

Keith Vanderlinde, Cherry Ng

Param num_gpus:

Int. Number of GPUs.

Param samples_per_data_set:

Int. Number of baseband samples corresponding to each buffer.

Param downsample_time:

Int. Number of time samples summed in the FRB kernels.

Param factor_upchan:

Int. Total upchannelization in the FRB kernels.

Param factor_upchan_out:

Int. Upchannelization that exits the FRB kernels, also number of freqs that will go into each output packet

Param num_beams_per_frb_packet:

Int. Number of FRB beam in each output stream. (?) Should be 4?

Param timesamples_per_frb_packet:

Int. Number of times that will go into each packet.

Param incoherent_beam:

Bool (default=false). Form the incoherent beam or not. If true, will stuff incoherent beam in position 0.

Param incoherent_truncate:

Float (default=1e10). To deal with inputs / times /freqs with anomalously high values, this limits values used prior to summing into the incoherent beam.

Public Functions

frbPostProcess(kotekan::Config &config_, const std::string &unique_name, kotekan::bufferContainer &buffer_container)

Constructor.

virtual ~frbPostProcess()

Destructor.

virtual void main_thread() override

Primary loop to wait for buffers, dig through data, stuff packets lather, rinse and repeat.