Toolchain: Workaround incorrect ELPA results with GCC 15.2 - #7784
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Toolchain: Workaround incorrect ELPA results with GCC 15.2#7784Growl1234 wants to merge 1 commit into
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A GCC 15.2 code-generation bug has caused ELPA's double-complex AVX/AVX2
BLOCK2kernels to return incorrect eigenvectors (marekandreas/elpa#77).The issue is reliably reproducible in an ELPA-only test and affects ABACUS LCAO multi-k calculations using
ks_solver = genelpa. The eigenvalues remain correct, but the returned eigenvectors have large residual and orthogonality errors, which can subsequently corrupt the density matrix, SCF convergence, total energy, forces, stress, and other wavefunction-dependent quantities.Affected systems include (at least) Fedora 42 and Ubuntu 26.04 LTS.
Rebuilding the affected ELPA C kernels with
-fno-tree-slp-vectorizerestores the residual and orthogonality errors to machine precision. Therefore, conditionally add-fno-tree-slp-vectorizeto ELPA'sCFLAGSwhen its C compiler is GCC 15.2.