Removed nested for loop, floats->doubles

[t-brandt]

Resolves JP-nnnn
Resolves RCAL-nnnn

Closes #

This PR removes a nested for loops in the Cython code, changing its cost from order nresultants^2 to order nresultants. It also promotes some floats to doubles within that routine, and removes the allocation of an unneeded array.

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • run regression tests with this branch installed ("git+https://github.com/<fork>/stcal@<branch>")
    • jwst regression test
    • romancal regression test

news fragment change types...

• changes/<PR#>.apichange.rst: change to public API
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.55%. Comparing base (728b877) to head (ccf2672).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #325      +/-   ##
==========================================
- Coverage   29.56%   29.55%   -0.01%     
==========================================
  Files          37       36       -1     
  Lines        8332     7949     -383     
==========================================
- Hits         2463     2349     -114     
+ Misses       5869     5600     -269     

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[schlafly]

Tim, can you add a change log entry, following this model? https://github.com/spacetelescope/stcal/pull/321/files#diff-65a8677afe9532023b50e0f3c9424360837e2b7f60693db564f8e3056ff5d4a5

Roman regtests are here: https://github.com/spacetelescope/RegressionTests/actions/runs/12379700686
They show some small differences likely related to numerical precision; I will investigate tomorrow. I've not run Webb regtests as it seems impossible that this could have any effect there, as ols_cas22 is not used?

Tim, do you want to ask someone running large ramps to test to see if this leads to the expected speed up?

[t-brandt]

I added a change log entry. That is correct; this code is not used at all in the JWST pipeline. And I asked RTB members to run romancal on this stcal branch to verify performance.