The Python Sky Model 3 software

The Python Sky Model (PySM) is a package used by Cosmic Microwave Background (CMB) experiments to simulate maps, in HEALPix pixelization, of the various diffuse astrophysical components Galactic emission relevant at CMB frequencies (i.e. dust, synchrotron, free-free and Anomalous Emission), as well itself. These maps may be integrated over given instrument bandpass smoothed with beam. PySM 2, released 2016, has become de-facto standard for simulating emission, example it CMB-S4, Simons Observatory, LiteBird, PICO, CLASS, POLARBEAR other experiments, shown 80+ citations 2 publication. As resolution upcoming increases, software started show some limitations, solution these issues was reimplement from scratch focusing on features: all models numba Just-In-Time compiler reduce memory overhead optimize performance; use MPI through mpi4py coordinate execution 3 across multiple nodes rely libsharp, distributed spherical harmonic transforms; employ data utilities infrastructure provided astropy download input templates cache them when requested. At this stage we strive maintain full compatibility therefore implement exact same naming scheme. In extensive test suite compare output each model results obtained 2.