Commit 7124e861 authored by Vacaliuc, Bogdan's avatar Vacaliuc, Bogdan
Browse files

plan/refactor-chi-scan-with-flying-callback-technique: implementation log 



Flip status from "awaiting implementation" to "implemented 2026-04-15 as
commit 206fbea on bl4b-scripts/flying-chi; awaiting T1 smoke test".

Add section 11 Implementation log capturing:
- deviation from plan section 5.1: output_csv parameter auto-saving to
  /SNS/users/6ov/BL4B/<date>/ (covers the section 6.4 CSV post-mortem
  requirement automatically);
- the edit-and-run finding: a def main()/__main__ refactor was proposed
  and reverted after the beamline scientists confirmed the folder
  standardises on flat edit-and-run scripts, with the convention now
  captured in bl4b-scripts/CLAUDE.md on the flying-chi branch;
- remaining TODOs: T1-T5 smoke tests (section 6.2), section 10 back-port
  of try/finally save/restore to flying_z.py, optional spin-off of
  measure_slew_rate into a separate importable helpers module.

Co-Authored-By: default avatarClaude Opus 4.6 (1M context) <noreply@anthropic.com>
parent 30d54016

plan/refactor-chi-scan-with-flying-callback-technique.md

+74 −2
Original line number Diff line number Diff line 
# Refactor CHI_scan.py using flying_z.py's camonitor + timestamp correlation



**Date:** 2026-04-15

**Branch:** bl4b-alignment-integration (tasking) → a new branch on `bl4b-scripts` (submodule, currently `ScriptScan/2026A`)

**Branch:** bl4b-alignment-integration (tasking) → `flying-chi` branch of `bl4b-scripts` submodule

**Target output:** `bl4b-scripts/flying_chi.py`

**Status:** Plan — awaiting implementation

**Status:** Implemented 2026-04-15 as commit `206fbea` on `bl4b-scripts/flying-chi`. **Awaiting T1 beam-off smoke test (§6.2)** as next operator action — all remaining TODOs live in §6.2 (T1–T5) and §10 (flying_z.py back-port). See §11 "Implementation log" at the bottom for deviations from the plan.



---
@@ -554,3 +554,75 @@ their own ticket (not blocking flying_chi): 
  `EventRate_RBV` is plumbed in the same Stats plugin. Q5 only probed the

  profile PVs. Worth a separate diagnostic on `EventRate_RBV` alone to

  confirm flying_z's 10 ms setting isn't silently under-sampling.



---



## 11. Implementation log



### 2026-04-15 — Initial commit



Implemented as commit `206fbea` on branch `flying-chi` of `bl4b-scripts`:

`flying_chi.py` matches the layout in §4, the PV set in §5.5, the callback

design in §5.4, the save/restore in §5.6, the post-process in §5.7, the fits

in §5.8 with FitXdist as the primary move (§7, first bullet: unconditional X

wins, matches CHI_scan.py — documented in the module docstring), the §5.9

move-to-fit safety check, and the §5.10 plotting style including the σ_X(t)

vs chis(t) twin-axis diagnostic.



**Deviation from §5.1 (user-editable parameters):** added a diagnostic

output CSV path parameter `output_csv`, auto-named with the current date

under `/SNS/users/6ov/BL4B/<date>/flying_chi-<HHMMSS>.csv`. Write is wrapped

in try/except so a permission error or missing parent directory downgrades

to a console warning rather than aborting the scan. The §6.4 requirement

("save `(tCHI, vCHI, sX, sY, intensity)` to a CSV so the agent can

post-mortem the fit quality") is therefore automatic, not operator-managed.



### 2026-04-15 — Edit-and-run idiom, no `__main__` guard



A follow-up session proposed wrapping the scan body in

`def main(): ...` + `if __name__ == "__main__": main()` so the operator

could `from flying_chi import measure_slew_rate` in an IPython shell

without triggering the scan. The refactor was implemented and then

**reverted** after the operator consulted with the beamline scientists:



> *"The scientists seemed uncomfortable changing to this method when the

> remaining scripts in this folder are strictly edit-and-run."*



The convention across `bl4b-scripts/` (CHI_scan.py, CHI_measurement.py,

Script_scan_*.py, Solid_theta_alignment_*.py, flying_z.py, flying_chi.py,

theta_rough_align.py, move_align.py, ...) is that every script executes

top-to-bottom at module scope. Scientists `%run script.py` (or `%edit` +

`%run`) and expect re-running to re-execute the scan every time. A

`__main__` guard would silently change the meaning of `%run` for one

outlier in the folder.



**Captured as folder-wide convention** in `bl4b-scripts/CLAUDE.md` on the

`flying-chi` branch (deliberately NOT merged into deployed branches like

`ScriptScan/2026A` — those are user-facing on the instrument and keep no

agent-facing docs in their working tree).



**Implication for future work on flying_chi.py:** if any helper in this

file ever genuinely needs to be importable without side effects

(`measure_slew_rate`, `sigma_of_profile`), promote it into a separate

file in `bl4b-scripts/` rather than adding a `__main__` guard to

flying_chi.py itself. Same rule applies to the other edit-and-run

scripts in this folder.



### Open TODOs (tracked here, actioned by future sessions)



1. **T1–T5 smoke tests (§6.2).** First operator action is T1: beam-off,

   narrow range, low velocity, verify (a) monotonic sweep, (b) restore

   integrity, (c) ≥30 samples per profile PV. Pre-flight PV availability

   probe (`./setup/archiver-query.sh --search 'BL4B:Mot:chis*'`) is

   called out in §6.3 — run that once before T1.

2. **§10 back-port to flying_z.py.** Once T1–T5 validate the try/finally

   save/restore pattern, port it to `flying_z.py` (which currently mutates

   `HS.VELO` / `HS.VMAX` without restoring). Separate diagnostic on

   `EventRate_RBV` at 10 ms cadence recommended before deciding whether

   to change flying_z's 10 ms default.

3. **Optional importable-helpers spin-off.** If the operator ever asks

   for a way to run `measure_slew_rate` interactively without editing

   flying_chi.py down to just that function first, factor it (and

   possibly `sigma_of_profile`) into `bl4b-scripts/flying_helpers.py`

   or similar. Not blocking — current operator workflow is to edit

   the scan parameters inside flying_chi.py and rerun.