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DSTEBR and SSTEBR compute all eigenvalues of a real symmetric
tridiagonal matrix with a values-only divide-and-conquer method.
Only the first and last boundary rows of each local eigenvector
block are propagated across merge levels, so no *LAEDA-style
full-block store/replay is needed.
The workspace is O(N): LWORK >= 16*N and LIWORK >= 7*N for
N > SMLSIZ; blocks with N <= SMLSIZ fall back to *STERF. DSTEBR
and SSTEBR are new routines and do not change the behavior of
*STEDC or *STERF.
Private helpers: *LAED0_BR, *LAED4_BR, *LAED7_BR/*LAED8_BR and
*LAED9_BR.
DCHKST and SCHKST gain test (38):
| D1 - D5 | / ( |D1| ulp ), with D1 from *STEQR('V').
LAPACKE gains LAPACKE_dstebr, LAPACKE_sstebr and their _work
variants (workspace query, LP64 and ILP64).
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #1424 +/- ##
==========================================
- Coverage 69.33% 69.18% -0.16%
==========================================
Files 6122 6136 +14
Lines 487027 488227 +1200
Branches 23268 23282 +14
==========================================
+ Hits 337686 337766 +80
- Misses 148903 150023 +1120
Partials 438 438
... and 1 file with indirect coverage changes Continue to review full report in Codecov by Harness.
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langou
previously approved these changes
Sep 26, 2026
Fixes -Werror=conversion (INTEGER(8) to REAL(4)) in the -fdefault-integer-8 builds. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Author
|
Fixed the -fdefault-integer-8 conversion error in SSTEBR, could you approve the workflow run? |
langou
approved these changes
Sep 27, 2026
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Description
This adds two new routines,
DSTEBRandSSTEBR, that compute alleigenvalues of a real symmetric tridiagonal matrix with a values-only
divide-and-conquer method.
Only the first and last boundary rows of each local eigenvector block are
propagated across merge levels, instead of storing complete secular
eigenvector blocks for
*LAEDA-style replay. The workspace is thereforeO(N):
LWORK >= 16*N,LIWORK >= 7*NforN > SMLSIZN <= SMLSIZfall back to*STERFSTEBR= Symmetric Tridiagonal Eigenvalues, Boundary-Row DC.New files
SRC/dstebr.f,SRC/sstebr.f— public driversSRC/dlaed0_br.f/SRC/slaed0_br.fSRC/dlaed4_br.f/SRC/slaed4_br.fSRC/dlaed7_br.f/SRC/slaed7_br.f(contains*LAED8_BR)SRC/dlaed9_br.f/SRC/slaed9_br.fLAPACKE/src/lapacke_dstebr.c,lapacke_sstebr.cand their_workvariantsUpdated files
SRC/Makefile,SRC/CMakeLists.txt(SCLAUX,DZLAUX)TESTING/EIG/dchkst.f,TESTING/EIG/schkst.f: new test (38),| D1 - D5 | / ( |D1| ulp )withD1from*STEQR('V'), same style astests (12) and (26)
LAPACKE/include/lapack.h,LAPACKE/include/lapacke.h,LAPACKE/include/lapacke_64.h,LAPACKE/src/Makefile,LAPACKE/src/CMakeLists.txtDOCS/groups-usr.dox: newstebrgroupTesting
Built with
gfortranusingmake.inc.example, run with the standardTESTINGdrivers and summarized withlapack_testing.py:dsep.out/ssep.outnow report 4560 DST/SST tests per NB setting(4440 before test (38)), all passing
Test (38) only enters the new code for
N > SMLSIZ.TESTING/sep.intopsout at
N = 20, so there it exercises the*STERFfallback; with anenlarged input (
N = 64, 128) test (38) does exercise*LAED0_BR, andfails as expected when
DSTEBRis deliberately perturbed.The new sources compile clean with the CI flag sets
(
-Werror=conversion,-fimplicit-none,-fcheck=all,-pedantic), theC wrappers with
-Wall -pedantic-errors, and the routines pass-fcheck=allat run time. The only remaining warning is-Wmaybe-uninitializedonJLAM, whichSRC/dlaed8.fproduces as well.Compatibility
No existing public interface changes, and no change to
*STEDCor*STERFbehavior.
Checklist