v0.5.0

Breaking Changes

• Lqe, Kalman, Kalmd now accept *RiccatiOpts as final parameter for workspace reuse

Performance Optimizations

Riccati Solvers (Care/Dare)

• RiccatiWorkspace struct pools ~25 arrays, reducing GC churn by ~96% (1.95 MB/call eliminated)
• Care_N10: 54,640 → 994 B/op, Dare_N10: 63,784 → 906 B/op

HinfNorm

• Replace 50x per-frequency EvalFr+SVD loop with single vectorized Sigma() call
• 43% faster, 95% less memory, 83% fewer allocs

Transfer Functions

• Pool vPolyRecurrence allocations: 25% fewer allocs per matrix transformation

FeedbackLFT

• Scoped BLAS workspace eliminates ~48 intermediate allocations (321 → 273 allocs/op)

Balreal / Balred

• Single unified buffer replaces 17 make() calls (104 → 88 allocs/op)

ControllabilityStaircase

• Static blockBuf eliminates per-iteration mat.NewDense (126 → 109 allocs/op)

Raw Stride Indexing

• Replace At()/Set() with direct RawMatrix().Data indexing in transfer.go, frequency.go, feedback_lft.go hot paths

Lqr/Kalman Workspace Propagation

• Lqe/Kalman/Kalmd proxy RiccatiOpts to inner Care/Dare calls
• Kalman_N100: 2,213 Ki → 309 Ki B/op (86% reduction)

v0.4.0

Breaking Changes

• System.InternalDelay, System.B2, System.C2, System.D12, System.D21, System.D22 fields replaced by System.LFT *LFTDelay nested struct
  • sys.InternalDelay → sys.LFT.Tau
  • sys.B2 → sys.LFT.B2 (same for C2, D12, D21, D22)
  • nil check: sys.LFT == nil replaces individual field checks

Improvements

• Add copyStrided/copyBlock matrix copy helpers, eliminating ~100 duplicate inline copy loops
• Unify duplicate extractBlock/extractSubmatrix functions
• -3.5% benchmark geomean improvement across 101 benchmarks (up to -17% on delay operations)
• Net -51 lines of code

Tests & Coverage

• Add MATLAB delay system tests (Pade, Thiran, c2d, feedback, margins)
• Add exact MATLAB/python-control expected values to all tests
• Tighten test tolerances
• Coverage 83.9% → 85.7%

Other

• Update README with full API coverage

v0.3.0

Performance & Robustness

Simulation hot-path optimizations

• Replace gonum MulVec/AddVec wrappers with direct blas64.Gemv calls in simulateNoDelay (-22%) and simulateWithInternalDelay (-74%)
• Fuse A*x + B*u into Gemv(beta=1) accumulation, eliminating intermediate buffers

Frequency response allocation reduction

• Add TransferFunc.evalInto for allocation-free transfer function evaluation
• FreqResponse allocs -71% (560→160), Bode allocs -81% (992→192)

Numerical robustness (#347510c)

• Harden numerical robustness and close test coverage gaps

Simulation performance (#4429669)

• Batch delayed MIMO simulation to remove per-input replay overhead (#2)

New benchmarks

• 7 MATLAB-inspired benchmarks: DC motor, Boeing 747 lateral/longitudinal, mass-spring-damper chain, large system (50 states), feedback+simulate pipeline, large MIMO Bode

v0.2.0

Bug Fixes

• Fix DiscretizeZOH silently dropping InternalDelay (#1)

  DiscretizeZOH and Discretize now properly handle systems with internal delays (LFT structure produced by Feedback with delays in the feedback path).

  Two underlying bugs fixed:

  • DiscretizeZOH/Discretize silently discarded the LFT delay structure (B2, C2, D12, D21, D22, InternalDelay), reducing the system to its delay-free rational part — causing S ≈ 1 and T ≈ 0 instead of correct sensitivity functions.
  • discretizeWithInternalDelay copied the continuous-time B2 unchanged instead of computing Bd2 = Γ·B2 via the augmented matrix exponential, making the delayed feedback gain ~20× too large.

v0.1.0

Initial release: Go library for linear state-space control systems.