Release 4.3a1

🚀 GTSAM 4.3a1 is a major incremental release featuring:
• Significant documentation expansion and new docs site
• New Lie groups, kernels, and IMU EKF infrastructure
• Strong Hybrid, Discrete, and Navigation improvements
• Broad Python wrapping advances
• A large number of bug fixes, CI upgrades, and toolchain improvements
• We removed GeographicLib as a 3rd party vendor

🧰 Core Features & New Math
• Matrix Lie Group infrastructure (MatrixLieGroup, traits, kernels) and SO(3) kernels.
• New Lie groups: Gal3, SL4, major updates to Similarity2/3.
• ExtendedPriorFactor, ConcentratedGaussian, FrobeniusBetweenFactorNL.
• Exact Zero-Order Hold IMU integration, centripetal-accel tests, and NavState + IMU EKF.
• Gal3 IMU EKF implementation.
• Constrained optimizers added.
• Discrete-Continuous Smoothing and Mapping.
• DiscreteScenario framework.

📚 Documentation & Examples
• Major docs refresh: navigation, discrete, geometry (Cal3_S2, Cal3DS2_Base, Cal3_S2Stereo, StereoCamera), concepts, IMU EKF, Invariant EKF draft.
• New notebooks: LQR, iLQR, discrete examples, Python examples, standardized formats.
• Ported StereoVOExample (small & large), added small bearing-range example.
• Many contributions from new authors throughout.

🧩 Wrapping & Python
• Large set of wrap updates: HybridValues, HybridBayesNet/HybridConditional, Cal3DS2_Base, Gal3, SL4, Similarity2/3, more.
• Added GTSAM_USE_SYSTEM_PYBIND, updated to pybind11 3.0.1.
• Added templates for IMU backend selection (no compiler flags).
• Improved custom wrapper extension instructions.
• Fixed python wheel building.

🔧 Bug Fixes & Cleanup
• Removed static identity matrices in LAGO (memory-safety fix).
• Fixed memory bugs in Hybrid tests.
• Fixed constructor reset issues, bias handling, IMU factors example, preintMeasCov reset.
• Many compile-warning cleanups across GCC/Clang/MSVC.
• Fixed shadowed operators, size_t misuse for Key, Eigen5 compatibility, and misc timing issues.
• Removed obsolete fields in Cal3, dimensional cleanup.
• Numerous link and doc fixes (Pose2 docs, README, notebooks).
• Eliminated outdated brew taps, cephes linking issues, and boosted robustness of discrete modules.

🏗️ CI, Build, and Tooling
• Massive CI overhaul: vcpkg improvements, sccache for Windows, Docker-based CI, faster pipelines.
• Added vcpkg CI, fixed macOS build, improved cache, reinstated eigen3.
• Windows: /permissive- enabled, excluded flaky tests, fixed single-exe linking.
• Removed dependency on Boost in ROS package.xml.
• Introduced QP tests without Boost.
• Better timing with TBB and GCC fixes.
• Added logs-on-failure, fixed merge CI, updated INSTALL docs.

Full change list

• (Update wrap) add functionality to pull docs from parent classes by @p-zach in #2118
• docs: Add Invariant Kalman Filtering to navigation.md by @scottiyio in #2147
• Update navigation.md by @scottiyio in #2149
• Discrete-Continuous Smoothing and Mapping by @varunagrawal in #2078
• Updated wrapper for HybridValues by @dellaert in #2150
• Fix paths in notebooks by @dellaert in #2153
• Wrap HybridBayesNet and HybridConditional methods by @dellaert in #2152
• Remove static identity matrices in lago.cpp to avoid memory corruption in downstream tasks by @BITVoyager in #2091
• Fixed SLAM Example link in Pose2 Doc by @CodeXTL in #2155
• Fix compiler warning of operator being shadowed by @ProfFan in #2158
• Added user guide for geometry/Cal3_S2 by @CodeXTL in #2156
• Fix misuses of size_t for gtsam::Key by @ProfFan in #2162
• Updated Cal3_S2 User Guide by @CodeXTL in #2163
• add constrained optimizers by @yetongumich in #1980
• Add vcpkg ci by @talregev in #2164
• Fix for Issue #2161 in borglab/gtsam by @DanielChaseButterfield in #2168
• Add template for IMU backend selection to move away from compiler flag by @p-zach in #2157
• Hybrid Fixes by @varunagrawal in #2170
• Markdown documentation draft PR for InvariantEKF by @scottiyio in #2151
• ROS package.xml: do not depend on boost by @jlblancoc in #2171
• Updated geometry.md and Minor Fixes by @CodeXTL in #2172
• Fix constructor preintMeasCov reset by @p-zach in #2174
• Removed dimension field from Cal3 by @CodeXTL in #2178
• Updates to Similarity2 and Similarity3 by @dellaert in #2180
• Add GTSAM_USE_SYSTEM_PYBIND option and improve cache for vcpkg by @talregev in #2182
• Similarity2 and Similarity3 updates by @dellaert in #2183
• Add Gal3 wrapper and... by @dellaert in #2184
• Add friendly instructions for custom wrapper extensions by @p-zach in #2189
• Updated Cal3DS2_Base python wrapper by @CodeXTL in #2188
• Ported StereoVOExample by @CodeXTL in #2186
• Fix Memory bug in Hybrid Tests by @dellaert in #2194
• Test both PIM variants by @dellaert in #2193
• Fix timing if no boost by @dellaert in #2191
• MatrixLieGroup implementation and traits by @dellaert in #2187
• Bespoke vec methods by @dellaert in #2192
• Ported StereoVOExample_large and Edits to StereoVOExample by @CodeXTL in #2195
• Added User Guides for Cal3_S2Stereo and StereoCamera by @CodeXTL in #2200
• Remove initial cov from CombinedImuFactor by @dellaert in #2199
• Increase maxIterations in Cal3DS2_Base.cpp calibrate function by @steplee in #2204
• Fix examples using biasAccOmegaInt by @varunagrawal in #2205
• Add DiscreteScenario by @p-zach in #2201
• Add reference to wrap docs by @p-zach in #2206
• Created jupyter notebook for the LQR example. by @zhangzdd in #2160
• iLQR example notebook by @zhangzdd in #2196
• Add SL4 to geometry by @dellaert in #2207
• Concepts documentation and remove Dim/dim by @dellaert in #2209
• Refactor AHRSFactor by @dellaert in #2210
• Add Gal3 and SL4 docs by @dellaert in #2214
• Fix all compile warnings on ubuntu_latest by @dellaert in #2217
• Exclude windows tests by @talregev in #2220
• Remove cxx_flags by @talregev in #2223
• Fix single exe linking by @dellaert in #2224
• Kernels for SO3 by @dellaert in #2226
• Use Kernels, deprecate old methods by @dellaert in #2227
• CI Improvements for speed by @dellaert in #2229
• Fix Boost and badges by @dellaert in #2232
• Port eval to other repo by @p-zach in #2228
• Add gtsam unstable tests in vcpkg by @talregev in #2234
• FrobeniusBetweenFactorNL, and better noise API by @dellaert in #2236
• Remove outdated brew tap (was required for boost versions) by @ProfFan in #2245
• Update README.md: fix minimum cmake version by @jlblancoc in #2243
• Remove metis and geographiclib ports from vcpkg ci by @talregev in #2244
• Fix CI on merge by @dellaert in #2246
• Add Gal3 wrapping by @dellaert in #2247
• NavState + IMU EKF by @dellaert in #2242
• Fix building of python wheels by @dellaert in #2248
• Documented NonlinearOptimizerParams in the NonlinearOptimizer doc by @rafaelspring in #2250
• Bug fix imu factors example by @jaffarrell in #2254
• Discrete docs by @dellaert in #2257
• Fix tests and simplify Windows CI by @Gold856 in #2256
• More notebooks in discrete by @dellaert in #2258
• Add some more examples by @dellaert in #2259
• Fix vcpkg macos. Upload vcpkg logs on failure by @talregev in #2262
• Fix CI and run non-boost QP tests by @dellaert in #2260
• Exact zero-order hold IMU integration by @dellaert in #2261
• Formatting/naming in Nav by @dellaert in #2263
• Gal3 IMU EKF class & header by @scottiyio in #2251
• temporary remove eigen3 from vcpkg by @talregev in #2267
• Remove GeographicLib as a 3rd party vendor by @nebudev14 in #2253
• Add GeographicLib to vcpkg by @talregev in #2282
• ExtendedPriorFactor and ConcentratedGaussian by @dellaert in #2266
• Use sccache to cache Windows release builds by @Gold856 in #2274
• Add tests to ensure centripetal accel is dealt with properly for IMUs offset from body frame by @scottiyio in #2281
• Update wrap to latest with pybind11 3.0.1 by @ProfFan in #2277
• Remove python excluded tests on windows vcpkg by @talregev in #2271
• Add vcpkg compilation with gtsam in INSTALL.md doc by @talregev in #2269
• Fix compatibility for Eigen 5.0.0 by @cybaol in #2265
• Cast Eigen::Matrix dimension type to int by @varunagrawal in #2284
• Documentation Updates by @Robert-Jia00129 in #2285
• Small example for bearing-range by @dellaert in #2286
• CI using Docker by @suveergarg in #2065
• Fix cephes static linking by @Gold856 in #2273
• 6 More Python Examples + Standardized Notebook Format by @rohan-bansal in #2288
• Enable and propagate /permissive- on MSVC by @Gold856 in #2268
• Add back eigen3 to vcpkg by @talregev in #2289
• Remove temporary eigen3 by @talregev in #2293
• Remove cephes dllexport.h from cmake by @talregev in #2294
• Fix timing with TBB and a minor GCC bug by @ProfFan in #2296

New Contributors

• @BITVoyager made their first contribution in #2091
• @CodeXTL made their first contribution in #2155
• @DanielChaseButterfield made their first contribution in #2168
• @steplee made their first contribution in #2204
• @zhangzdd made their first contribution in #2160
• @rafaelspring made their first contribution in #2250
• @jaffarrell made their first contribution in #2254
• @nebudev14 made their first contribution in #2253
• @cybaol made their first contribution in #2265
• @suveergarg made their first contribution in #2065
• @rohan-bansal made their first contribution in #2288

Full Changelog: 4.3a0...4.3a1