nifty-ls evaluates the Lomb-Scargle periodogram very quickly and accurately. The Lomb-Scargle periodogram, used for identifying periodicity in irregularly-spaced observations, is useful but computationally expensive. However, when it is phrased mathematically as a pair of non-uniform FFTs (NUFFTs), FINUFFT (ascl:2412.007), which is really fast, can be leveraged to improve performance. It also enables GPU (CUDA) support and is several orders of magnitude more accurate than Astropy's (ascl:1304.002) Lomb Scargle with default settings.

pycorr wraps two-point counter engines such as Corrfunc (ascl:1703.003) to estimate the correlation function. It supports theta (angular), s, s-mu, rp-pi binning schemes, analytical two-point counts with periodic boundary conditions, and inverse bitwise weights (in any integer format) and (angular) upweighting. It also provides MPI parallelization and jackknife estimate of the correlation function covariance matrix.