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GeezerVison is showing github.com — Validate discrete gain crossovers on the unit circle by galleonli · Pull Request #1273 · python-control/python-control

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@galleonli

@galleonli galleonli commented Nov 10, 2026 •
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The old tolerance grew with system order, so points where the gain was well below 1 could still count as crossovers. That led to incorrect phase margins.

This change checks the gain again on the unit circle. When a candidate is slightly off, it solves for a nearby root and keeps the point only if the gain is close to 1.

All five new regression cases fail on main and pass with this change. The local margin, FRD, transfer-function, and LTI tests finished with 419 passed and 130 skipped.

I used OpenAI Codex to write the patch and regression tests and run the local checks.

Refs #1266.

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@galleonli
Validate discrete gain crossovers on the unit circle
7f66cc9
@slivingston

slivingston commented Nov 11, 2026

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@galleonli Can you run the checks locally yourself, without using OpenAI ? Just confirming as a proof-of-understanding.
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@galleonli

galleonli commented Nov 11, 2026

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@galleonli Can you run the checks locally yourself, without using OpenAI ? Just confirming as a proof-of-understanding.

Sure! I ran all four test modules locally myself: 419 passed, 130 skipped.
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@slivingston
slivingston self-requested a review November 11, 2026 22:40
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@galleonli @slivingston
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