Global apply_fractal (dcell **xout, const void *extra, const dcell *xin, real alpha, int xb, int yb): : this is not thread safe.
Global apply_invpsd (dcell **xout, const void *extra, const dcell *xin, real alpha, int xb, int yb): : this is not thread safe.
File gensei.h: find ways to factor in outerscale effect (use von karman spectrum instead of kolmogorov)
Global ngsmod_remove (sim_t *simu, dcell *dmerr): handle 3 DM case.
Global perfevl (sim_t *simu): Write a standalone routine that can plot results, using techniques developped in drawdaemon.
File powfs.h: isolate DTF, ETF, routines, make then generic interface and relocate to the lib folder.
File powfs_utils.h: find ways to factor in outerscale effect (use von karman spectrum instead of kolmogorov)
Global tomo_cfg_t::alg: implement BGS, MG 0: Cholesky direct solve for the large matrix. (CBS) 1: CG or PCG. 2: SVD or EVD: Eigen value decompsition