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Chris Ford has an encoder simulator in lab3, with documentation here:  UDP Encoder Interface (rix Mono Encoder).  He also has committed lab3-caf-encoder.cnf to lcls2 GitHub in psdaq/psdaq/cnf/.

High Rate Mono Encoder Interpolation Options

Goal: keep the parallelization happy (both ami and mpi-psana) so that every shot has an encoder value (either real or interpolated)

• ~5kHz of measured data is roughly the maximum readout rate
• interpolation will make the data better

Example motor motion:

Image Added

Options:

• DAQ interpolation.  Ugly DAQ C++
• psana interpolation in-memory
  • on SMD0 core (would dramatically complicate our most complicated psana event-builder code)
  • psana "broadcasts" all the encoder data to all the cores.  quite messy and would affect performance unless SlowUpdate broadcast at 10Hz was feasible
• psana post-processing interpolation written to a new xtc2 file
• (doesn't work because of chaos caused by batching, deadtime, arbitrary number of cores, load-balancing) DAQ repeats without interpolation.
  • Ideally xtc2 would be able to say 3 (repeats 5 times) 7 (repeats 5 times).  xtc2 can't say this easily.
  • (preferred) or another version would be 3(deltatime=0),3(+deltatime),3(+deltatime),3,3,7,7,7,7,7,.... each core could do it's own interpolation.  provides flexibility and scalability.  extra data volume isn't too bad.  will make user code more complex (they will have to "buffer")