Accelerating Spherical Harmonic Transforms for a Large Number of Sky Maps

The spherical harmonic transform is a powerful tool in the analysis of spherical data sets, such as cosmic microwave background data. In this work, we present a new scheme for spherical harmonic transforms that supports both CPU and GPU computations, which is especially efficient on a large number of sky maps. By comparing our implementation with the standard Libsharp-HEALPix program, we demonstrate a 2-10 times speedup for the CPU implementation, and an up to 30 times speedup when a state-of-the-art GPU is employed. This new scheme's software package is available via an open-source GitHub repository.