Active development of this package has stopped. The package will receive bug fixes if necessary, but otherwise the code has been integrated into the ducc0 package (https://gitlab.mpcdf.mpg.de/mtr/ducc), and further development is taking place there.

Please prefer ducc0 over libsharp2 if you are starting a new project!

Library for efficient spherical harmonic transforms at arbitrary spins, supporting CPU vectorization, OpenMP and MPI.

https://arxiv.org/abs/1303.4945

This update features significant speedups thanks to important algorithmic discoveries by Keiichi Ishioka (https://www.jstage.jst.go.jp/article/jmsj/96/2/96_2018-019/_article and personal communication).

These improvements reduce the fraction of CPU time spent on evaluating the recurrences for Y_lm coefficients, which means that computing multiple simultaneous SHTs no longer has a big performance advantage compared to SHTs done one after the other. As a consequence, libsharp's support for simultaneous SHTs was dropped, making its interface much simpler.

With the proper compilers and flags (see the file COMPILE for details) libsharp2 is now built with support for SSE2, AVX, AVX2, FMA3, FMA4 and AVX512f and the appropriate implementation is selected dynamically at runtime. This should provide a very significant performance boost for everyone using pre-compiled portable binaries.

The library uses the standard autotools mechanism for configuration, compilation and installation. See the file COMPILE for configuration hints.