healpix_resample.psf.least_squares_cg

healpix_resample.psf.least_squares_cg(M, MT, y, x_ref, x0, max_iter=200, tol=1e-06, damp=0.0, verbose=True)

Solve for delta in a damped least-squares problem without forming dense matrices.

We solve:

(MT @ M + damp*I) delta = (y - x_ref @ MT) @ M

Shapes:

M : (N, K) sparse CSR MT : (K, N) sparse CSR y : (B, N) x_ref : (B, K) delta : (B, K)