Method for evaluating the lensing B-modes on the curved-sky to leading order in their perturbative expansion, given sets of observed (and Wiener-filtered) E-mode and lensing potential alm's. This fast implementation drinks heavily from D.Hanson's Quicklens code used in the Planck 2015 lensing analysis and itself based on the position-space approach of Dvorkin & Smith. See curved_sky_B_template_implementation_notes.pdf for mathematical details.
import csbt
B_template_vlm = csbt.weights.B_template_weights(np.ones(lmax+1)).eval_fullsky(wiener_filtered_phi_alm, wiener_filtered_e_alm)
# Extract the gradient and curl modes. Discard the latter.
g_B_alm, c_B_alm = csbt.shts.util.vlm2alm(B_template_vlm)
where wiener_filtered_phi and wiener_filtered_e_alm are numpy arrays of length lmax containing the Wiener-filtered a_{lm}^{\phi} and a_{lm}^{E, obs}.
The code can be run either from this directory, or installed by
running python setup.py install.
The code is primarily written in Python, although some low level spherical harmonic transform (SHT) routines are written in Fortran for speed. In order to use these SHT routines, the code must be compiled. This is done automatically when installing, however if running the code without installing it needs to be built with
python setup.py build_ext --inplace
Depending on system, you may need to specify a fortran compiler. For example
python setup.py build_ext --inplace --fcompiler=gnu95