[Wien] installing mpich and fftw before installing wien2k

[Gavin Abo]

> I just want to know why  fftw and mpich should be installed before 
> installing wien2k12.
> Are they necessary for doing the calculation parallel?

For mpi-parallel calculations, you must have them.

For serial and k-point parallel calculations, they are not needed. The 
non-mpi calculations use WIEN2k's fftpack, but you can optionally use 
fftw, which might give some calculation speedup as described in section 
11.1.1 on page 218 of the WIEN2k 16.1 usersguide [ 
http://susi.theochem.tuwien.ac.at/reg_user/textbooks/usersguide.pdf ].

The fftw is needed before the WIEN2k install so that its header and 
library files can be compiled and linked together with the WIEN2k code.

The mpich is needed before the WIEN2k install so that the environment, 
such as bin path, can configured during the WIEN2k installation.

> should I install Mpich and Fftw according to this fact that I want to 
> do the calculation in a single core?

No, a serial calculation is for a single core and it can be a waste of 
time to install them for two cores [ 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg03793.html 
].
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