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Fix uninitialized optimizer status for single-atom systems (gfortran bug) - #1441
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thfroitzheim
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Sep 4, 2026
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| add_test("xtb/Argparser_print_version" ${XTB-EXE} --version) | ||
| add_test("xtb/Argparser_print_help" ${XTB-EXE} --help) | ||
| add_test("xtb/Argparser_print_license" ${XTB-EXE} --license) |
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This isn't really command-line specific. Could you please move this into a optimization unit test (I don't think there is one present yet, but you can adapt one of the other unit tests)
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Replaced the command-line test with a TestDrive optimizer suite covering ANCopt, FIRE, and L-ANCopt for a single atom. All cases verify fail = .false. and iter_needed = 0.
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This should also be part of a unit test
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Removed lithium.xyz; the single-atom Li+ molecule is now constructed directly in the unit test. All 30 xTB unit-test suites pass with gfortran.
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Summary
Fix a bug in geometry optimization for single-atom systems when xTB is compiled with gfortran.
The ANCopt, FIRE, and L-ANCopt routines return immediately when
mol%n == 1, because a single atom has no internal geometry to optimize. However, this return occurred before the output variablesfail,iter, and optionaliter_neededwere initialized.With gfortran,
failcould therefore contain an undefined.true.(or equivalent) value. The caller interpreted this as a failed geometry optimization, producing a non-convergence error and a nonzero exit status. Other compilers happened not to expose the issue consistently.Changes
failto.false.and the iteration count to zero before the single-atom early return in:iter_neededwhen present.The present changes should resolve #1440
Expected behavior
A command such as:
should complete successfully.