New feature: interleaved amplitude type

[TysonRayJones]

contributors: Ali Rezaei and Tyson Jones
release: v4

The backend and API will make use of an interleaved complex scalar type, in lieu of the current separation of real and imaginary components. This remains precision-agnostic, is interoperable between C and C++, and is compatible with GNU, MSVC, Clang, MPI, NVCC, HIP and Intel compilers (and with OpenMP, except on Windows *shudder*). See the architecture and a minimum demonstration of this feature here.

• developer benefits

  • Cleaner and smaller code; no more boilerplate for explicit complex arithmetic.
  • Enables seamless integration with external libraries (without needing expensive memory copies/reformats) such as cuQuantum, Thrust, cuBLAS, FFTW, GSL*, etc.

• security benefits

  • Less chance of bugs due to erroneous complex arithmetic.

• user benefits

  • Both C and C++ users can use their language's native overloaded complex type in their code, and pass them seamlessly to the QuEST API without casts.
  • Users can seamlessly pass QuESTS amplitudes to other libraries using standard complex, or which use the same (standard) memory latout.

[TysonRayJones]

Added in 4122a6e