Brief notes from a mtg on Oct. 4 2021 with Mona, Elliott, Seema, Iris, Seshu, Chris
Link to psana2 user-documentation is here: psana
- psana is now "dgram-type" driven (a.k.a "multirun" concept)
- "broadcast": calibration constants, configurations, 1Hz "slow update" transitions
- support destination/filter/srv callbacks
- support step scans
- support environment store (motor positions, temperatures broadcast in slow-update transitions
- psana now uses prometheus to gather performance-monitoring data
- psana supports four modes of running: single-file, shmem, serial, parallel (will also support running in daq/drp in the future)
- legion only needs to support parallel mode, but shouldn't interfere with the other modes
- not ideal: keep the callback interface for legion, vs. loop interface for psana?
- ideally run all tests: but could be difficult with two interfaces (callback/loop)
Legion Planning Meeting
April 26, 2022 with Mona, Elliott, Seema, Chris
We discussed 7 issues:
- SlowUpdate support
- Which interfaces to support? (callbacks? low-level psiter? event loops?)
- filter/destination callbacks on EB cores
- small hdf5 production support ("SRV" nodes)
- MTIP
- detectors that integrate over time (e.g. 5kHz camera with 1MHz high-speed-digitizer)
- Step support
Point (2) was discussed last since it depends on the ideas generated from conversations from the other points.
Conclusions:
- Legion will support SlowUpdate using a "region" for EB cores. Legion behavior will continue to be supported at runtime via the env variable PS_PARALLEL. This will require changes to SMD0 and EB.
- Legion will support callbacks (high-level interface) and psiter (low-level interface). mpi will stick with loops for now (will not support callback interface). Elliott has ideas for an improved callback interface (more of a map/reduce like spark) but that will be optional depending on Seema's time.
- Legion may require changes to support filter/destination callback
- Need to factorize mpi send/receive out of hdf5 handling code
- Use low-level psiter interface, and also move to Detector interface (currently using raw data interface to access)
- We think this will work for legion by reusing the psana behavior
- Need to add "beginstep/endstep" callbacks and perhaps put the step information in the SlowUpdate "region"?
As time permits Seema will do the legion-related work with advice from Mona, Elliott, Chris. Legion may not support all features of psana (depending on time constraints) but we will try.
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