User:Cantonios/3.4

• New support for bfloat16

The 16-bit Brain floating point format[1] is now available as Eigen::bfloat16. The constructor must be called explicitly, but it can otherwise be used as any other scalar type. To convert back-and-forth between uint16_t to extract the bit representation, use Eigen::numext::bit_cast.

 bfloat16 s(0.25);                                 // explicit construction
 uint16_t s_bits = numext::bit_cast<uint16_t>(s);  // bit representation
 
 using MatrixBf16 = Matrix<bfloat16, Dynamic, Dynamic>;
 MatrixBf16 X = s * MatrixBf16::Random(3, 3);

• New backends
  • HIP: added support for AMD ROCm HIP, unified with the previously existing CUDA code for a generic GPU backend.

• Improved support for half
  • Native support for ARM __fp16, CUDA/HIP __half, Clang F16C.
  • Better vectorization support across backends.

• Improved support for custom types
  • More custom types work out-of-the-box (see #2201[2]).

• Improved Geometry Module
  • Transform::computeRotationScaling() and Transform::computeScalingRotation() are now more continuous across degeneracies (see !349[3]).
  • New minimal vectorization support.

• Backend-specific improvements
  • SSE/AVX/AVX512
    • Enable AVX512 instructions by default if available.
    • New std::complex, half, bfloat16 vectorization support.
    • Many missing packet functions added.
  • GPU (CUDA and HIP)
    • Several optimized math functions added, better support for std::complex.
    • Option to disable CUDA entirely by defining EIGEN_NO_CUDA.
    • Many more functions can now be used in device code (e.g. comparisons, matrix inversion).