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Replace slycot (Fortran 77) with slicot (C11) via compatibility layer#1

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Replace slycot (Fortran 77) with slicot (C11) via compatibility layer#1
Copilot wants to merge 1 commit into
slicot-migrationfrom
copilot/review-replace-slucot-with-slicot

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Copilot AI commented Jan 31, 2026 •
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Overview

Replaces slycot (Fortran 77 SLICOT wrapper) with slicot (C11 SLICOT translation) throughout python-control. Uses a compatibility layer to minimize invasive changes.

Changes

Compatibility Layer (control/slicot_compat.py)

  • Wraps 24 slicot functions to match slycot API signatures
  • Handles parameter reordering, type conversions, and array slicing differences
  • Centralizes error handling via _check_info() pattern

API Compatibility Fixes

  • sb03od: Parameter reorder, omit unused n/m/Q params
  • ab09ad/ab09md/ab09nd: Add ordsel param, slice reduced-order outputs
  • ab13dd: Add fpeak_in param, extract scalars from arrays
  • ab13md: Cast ITYPE/NBLOCK to int32
  • tb01pd: Handle tol=None → 0.0
  • sb10ad: Return gamma_out as first value

Migration

  • Update all slycot imports → slicot_compat
  • Rename pytest markers: @pytest.mark.slycot / @pytest.mark.noslicot
  • Update pyproject.toml optional dependency

Example Usage

# Before
from slycot import sb03md

# After
from control.slicot_compat import sb03md
# API signature unchanged, works transparently

Test Results

430 passed, 1 skipped, 1 xfail (test sensitivity)

Original prompt

Review the last commit as it is replacing the slucot with slicot written in C11. Review throughly.

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Copilot AI changed the title [WIP] Review replacement of slucot with slicot in C11 Replace slycot (Fortran 77) with slicot (C11) via compatibility layer Jan 31, 2026
Copilot AI requested a review from jamestjsp January 31, 2026 13:53
@jamestjsp

jamestjsp commented Jan 31, 2026

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@copilot Is it following the same coding pattern as python control codebase?

Copilot AI commented Jan 31, 2026

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@copilot Is it following the same coding pattern as python control codebase?

The slicot_compat.py module mostly follows python-control coding patterns, with a few minor inconsistencies:

✅ Follows conventions:

  • Top-level import pattern with try-except blocks (same as mateqn.py, statefbk.py)
  • Array handling: .copy() then .asfortranarray() consistently applied
  • Module structure: header, docstring, imports, helpers, then functions
  • Custom exception classes (SlicotResultWarning, SlicotArithmeticError)

⚠️ Minor inconsistencies:

  1. Missing __all__: Other modules define exports (e.g., mateqn.py line 49, statefbk.py line 34), but slicot_compat.py doesn't
  2. Sparse docstrings: Functions like sb03md have minimal docs compared to rich docstrings in mateqn.py's lyap() (lines 56-98) with Parameters, Returns, and extended descriptions
  3. Unused ldwork parameters: Present in all wrappers but never used (legacy API compatibility)
  4. ValueError vs ControlArgument: Line 52 uses generic ValueError instead of ControlArgument from exception.py (line 34)

The core functionality and structure are solid—these are documentation/polish items rather than functional issues.

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