fasttransforms (spack): FastTransforms provides computational kernels and driver routines for orthogonal polynomial transforms. The univariate algorithms have a runtime complexity of O(n log n), while the multivariate algorithms are 2-normwise backward stable with a runtime complexity of O(nd+1), where n is the polynomial degree and d is the spatial dimension of the problem. 
Keywords: chebyshev|harmonics|jacobi|laguerre|legendre|proriol|spherical|spin|ultraspherical|zernike