API documentation#
The core implementation of sphericart is written in C++. It relies on templates and
C++17 features such as if constexpr to reduce the runtime overhead of implementing
different normalization styles, and providing both a version with and without derivatives.
Spherical harmonics and their derivatives are computed with optimized hard-coded expressions for low values of the principal angular momentum number \(l\), then switch to an efficient recursive evaluation. The API involves initializing a calculator that allocates buffer space and computes some constant factors, and then using it to compute \(Y_l^m\) (and possibly its first and/or second derivatives) for one or more points in 3D space.
This core C++ library is then made available to different environments through a C API.
This section contains a description of the interface of the sphericart library for the
different languages it supports.
Although the Julia API is not fully documented yet, basic usage examples are available here.