NGXhalf, NGZhalf

For charge densities and potentials, half the storage can be saved if one of these flags is used, since

$$A_q = A^*_{-q} \quad \mbox{and} \quad A_r = A^*_r.$$ (1)

To use a real to complex FFT you must specify -DNGXhalf for the serial version and -DNGZhalf for the parallel version. If -DNGXhalf is specified for the serial version the real to complex FFT is "simulated" by a complex to complex FFT.

Mind: If this flag is changed in the makefile, recompile all *.F files. This can be done typing

touch *.F
make vasp