Size limit for GFN-FF?

[johnwkeller54]

Attempted Opt of 153 waters with xtb --gfnff (v 6.7.1) gives an endless loop. 100 waters optimizes OK. 215 waters "segmentation fault".

[johnwkeller54]

Need to set environment variable, for example : export OMP_STACKSIZE=5G This is added to .bashrc, then do $source .bashrc.

[johnwkeller54]

This does not work on some Linux systems such a rocky linux 9 with xtb-6.7.1. Here are the relevant commands and output for an input.inp file with 645 atoms:

$ env | grep OMP*
$ OMP_STACKSIZE=10G
$ /usr/local/xtb-6.7/bin/xtb --gfnff input.inp --opt --parallel 8 > out.out
forrtl: severe (174): SIGSEGV, segmentation fault occurred
Image PC Routine Line Source
xtb 000000000046E88A Unknown Unknown Unknown
xtb 0000000002D1BD40 Unknown Unknown Unknown
xtb 0000000000690A20 xtb_gfnff_neighbo 417 neighbor.f90
xtb 000000000068C4F9 xtb_gfnff_neighbo 132 neighbor.f90
xtb 00000000006417AE xtb_gfnff_ini2_mp 115 gfnff_ini2.f90
xtb 0000000000615DDC xtb_gfnff_ini_mp_ 276 gfnff_ini.f90
xtb 0000000000675CEF xtb_gfnff_setup_m 77 gfnff_setup.f90
xtb 000000000057C141 xtb_gfnff_calcula 141 calculator.f90
xtb 0000000000739EB4 xtb_main_setup_mp 128 setup.f90
xtb 0000000000438156 xtb_prog_main_mp_ 588 main.F90
xtb 0000000000450EA2 MAIN__ 57 primary.f90
xtb 0000000000401E42 Unknown Unknown Unknown
xtb 0000000002D1298A Unknown Unknown Unknown
xtb 0000000002D14227 Unknown Unknown Unknown
xtb 0000000000401D05 Unknown Unknown Unknown

On the same machine, a 15-atom opt --gfnff job ran normally.

[johnwkeller54]

Previous entries on this subject indicated one also needs a "ulimit -s unlimited" entry in .bashrc. Doing that allowed xTB to run large systems on the above Rocky9 machine and another Rocky8 VM.

[foxtran]

main branch should work without adjusting environment

[johnwkeller54]

It does...if there are fewer than about 400 atoms. But, remove "export OMP_STACKSIZE=5G" from .bashrc; source .bashrc; "unset OMP_STACKSIZE". Then attempted optimization of an 800-atom system with xTB-GFNFF gives seg fault. (Rockly Linux 9.6, xtb 6.7.1, 64 GB system memory).

[johnwkeller54]

..then on the same machine, the .bashrc entries were restored, and a xTB-GFNFF molecular dynamics on an 800-atom system ran successfully.