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Posted: **Wed Jan 03, 2024 3:01 pm**

Dear VASP Forum,

I am currently configuring the compilation process for the VASP code and I came across the recommended settings for the fftlib library in the makefile.include.intel_omp template file shipped with vasp.6.4.2 source code. The relevant section is commented as "For the fftlib library (hardly any benefit in combination with MKL's FFTs)" but still provides recommended configuration settings.

This raises a question for me: if the benefit of using fftlib in combination with MKL's FFTs is acknowledged to be minimal, why are these settings recommended? Is there a specific scenario where it might be advantageous to use this combination? If the fftlib library is not recommended to be used with MKL's FFTs, is there an alternative configuration that should be considered?

Code: Select all

FCL = mpiifort fftlib.o -qmkl
CXX_FFTLIB = icpc -qopenmp -std=c++11 -DFFTLIB_USE_MKL -DFFTLIB_THREADSAFE
INCS_FFTLIB = -I./include -I$(MKLROOT)/include/fftw
LIBS += fftlib

Your clarification on this point will be greatly appreciated. Thank you.

Best regards,
Zhao

Posted: **Fri Jan 05, 2024 1:07 pm**

Dear Zhao,

The recommendations (and optional tags) in the makefile.include file are present to ensure that all options are presented to users while compiling VASP. Given the diversity of possible hardware and other libraries it is not straightforward for us to give a clear recommendation for all systems - which is why all relevant tags are placed in the makefile.include file.

Sudarshan

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Clarification on Recommended Configuration for fftlib Library.

Clarification on Recommended Configuration for fftlib Library.

Re: Clarification on Recommended Configuration for fftlib Library.