[Wien] Issues with -O3 optimization and ifx

[Straus, Daniel B]

On a recently compiled copy of version 24.1 (with all patches applied) using Intel ifx version 2025.30, I attempted to set up a calculation but encountered very strange issues with nn where it gave nonsensical distances between atoms. On an older computer where ifort was used to compile WIEN2k 24.1, the same cif worked fine in cif2struct, setrmt, nn, etc.

I tracked it down to a compiler flag issue related to using the -O3 optimization flag. Using -O instead of -O3 solved the problem, and now everything behaves as expected.

For what it is worth, my successful compiler flags are (the system has a Ryzen 9950x, hence the march=znver5 flag):
(for regular execution) -O -march=znver5 -traceback -assume buffered_io -FR -I$(MKLROOT)/include -ipo -fp-model=precise
(for parallel execution, linked to ELPA) -O -march=znver5 -traceback -assume buffered_io -FR -I$(MKLROOT)/include -ipo -fp-model=precise -static -fc=ifx

Hopefully, this message can save someone a few hours of troubleshooting down the line.


Daniel Straus
Assistant Professor
Department of Chemistry
Tulane University
5088 Percival Stern Hall
6400 Freret Street
New Orleans, LA 70118
(504) 862-3585
http://straus.tulane.edu/


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