Copy updated zero-pivot columns back in xLASYF and xLAHEF - #1433
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ACSimon33 merged 2 commits intoOct 4, 2026
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #1433 +/- ##
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+ Coverage 69.38% 69.39% +0.01%
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Files 6122 6122
Lines 487347 487627 +280
Branches 23268 23268
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+ Hits 338166 338410 +244
- Misses 148747 148783 +36
Partials 434 434
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ACSimon33
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Oct 4, 2026
ACSimon33
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Oct 4, 2026
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Description
Fixes #1432, reported by @Bruun97.
When a column becomes exactly zero after a blocked Bunch-Kaufman panel update, xLASYF/xLAHEF set INFO but leave the original column in A instead of copying the updated column from W. The returned factors can therefore fail to reconstruct the input even though INFO > 0 documents a completed, singular factorization.
Copy the updated column back to A in both triangle branches of SLASYF, DLASYF, CLASYF, ZLASYF, CLAHEF and ZLAHEF, matching the _rook/_rk siblings. The production change is 12 lines. The Hermitian routines still force the diagonal real, and non-singular paths are unchanged.
The existing CHKSY/CHKHE drivers now test a rank-one 2-by-2 block whose second pivot becomes zero during elimination. They check INFO and reconstruct the input with xSYT01/xHET01. Coverage includes upper/lower storage, all six routines, and both real and imaginary off-diagonal blocks for complex types. The checks respect the existing singular-matrix selection.
Native verification on current master with gfortran 13.3,
-fcheck=alland reference BLAS:lapack_testing.py.These runs used Linux x86_64. Other compilers and optimized BLAS were not tested.
Checklist