v4.4.1

Quaternionic v4.4.1

Diff since v4.4.0

Merged pull requests:

• Bump actions/checkout from 6 to 7 (#105) (@dependabot[bot])
• Bump the all-julia-packages group with 14 updates (#106) (@dependabot[bot])
• Add property-based tests and expand type coverage with eigendecomposition (#107) (@moble)

v4.4.0

Quaternionic v4.4.0

Diff since v4.3.0

Merged pull requests:

• Add KAN decomposition function (#104) (@moble)

v4.3.0

Quaternionic v4.3.0

Diff since v4.2.1

Merged pull requests:

• Bump codecov/codecov-action from 6 to 7 (#102) (@dependabot[bot])
• Add simpler Boost methods (#103) (@moble)

v4.2.1

Quaternionic v4.2.1

Diff since v4.2.0

v4.2.0

Quaternionic v4.2.0

Diff since v4.1.0

Merged pull requests:

• Add Rv and vR functions to compute boost velocities (#101) (@moble)

v4.1.0

Quaternionic v4.1.0

Diff since v4.0.1

Merged pull requests:

• Add Lorentz polar decomposition (RB/BR) and ℂ-part helpers (#100) (@moble)

v4.0.1

Quaternionic v4.0.1

Diff since v4.0.0

v4.0.0

Quaternionic v4.0.0

Diff since v3.1.1

Improved capabilities for handling complex quaternions (aka biquaternions), which are good models for the Lorentz group.

Breaking changes

• Changed behavior of abs, abs2, and hypot for complex quaternions to use the spinor norm (which returns a complex number) rather than the Euclidean norm
• Overloaded LinearAlgebra.norm and LinearAlgebra.normalize for quaternion types, rather than creating Quaternionic.norm and Quaternionic.normalize (I hadn't realized the LinearAlgebra versions existed.)

v3.1.1

Quaternionic v3.1.1

Diff since v3.1.0

Merged pull requests:

• Disable functions with conditionals for FastDifferentiation (#83) (@moble)

v3.1.0

Quaternionic v3.1.0

Diff since v3.0.1

Release Notes for Version 3.1.0

New Features

• Automatic Differentiation (AD) Enhancements:

  • Added compatibility with multiple AD backends, including ChainRules, Zygote, Enzyme, and Mooncake. (23c3be7, 5889c25, 4702d4f)
  • Introduced iszerovalue function to improve numerical stability in special cases. (516a099, 1238473, 4f37368, 0c48e31)
  • Added an rrule for scalar multiplication. (287b36d)
  • Improved AD compatibility for sqrt, exp, and log functions. (3562051, 15145c0, 2b3dbbe)

• Improved Quaternionic Differentiation:

  • Expanded and clarified the definition of quaternionic differentiation. (d675202)
  • Added more examples for reverse-mode rules (rrules). (269b340)

• Test Framework Enhancements:

  • Introduced TestItems for better test organization and selection. (f16d5bc, feac600)
  • Enabled testing across all supported AD backends. (5889c25)
  • Loosened tolerances and improved test output clarity. (ebb487a, 648ed6d)

---

Improvements

• Numerical Stability:

  • Improved stability and differentiability of exp and log functions. (15145c0)
  • Simplified and stabilized sqrt, especially for AbstractQuaternion{Float16} to avoid underflow. (3562051, 28da67a)

• Documentation:

  • Expanded and clarified documentation for basic functions. (af3adb0)
  • Added comments and explanations for special cases in log and sqrt. (ec3682b, 805b791)
  • Warned about Zygote's limitations with explicit quaternionic inputs/outputs. (d999e88)

• Code Simplification:

  • Streamlined code for differentiation and quaternionic operations. (1dd44ae)
  • Simplified sqrt implementation for better readability and performance. (3562051)

---

Bug Fixes

• Corrected module name in documentation (copy-paste error). (99ffb98)
• Disabled Zygote-specific rules in favor of ChainRulesCore for better compatibility. (d5ef700)
• Fixed compatibility bounds for Enzyme and Mooncake (for hypot). (836a5f1)

---

Miscellaneous

• Updated dependencies and ensured compatibility with the latest versions. (6276f8a)
• Added an alias for the dot product in documentation. (4c7e209)
• Improved build process by ensuring updates before building docs. (9b395ff)

---

Version Update

• Set version to 3.1.0.

Merged pull requests:

• Start using TestItems and update for FastDifferentiation (#75) (@moble)

Closed issues:

• angle returns different values for a unit quaternion and its antipodal quaternion (#79)