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| author | julie <julielangou@users.noreply.github.com> | 2015-10-22 04:39:19 +0000 |
|---|---|---|
| committer | julie <julielangou@users.noreply.github.com> | 2015-10-22 04:39:19 +0000 |
| commit | 6d3c6b3d719c4fa38f8321e398a8ab142c124f22 (patch) | |
| tree | ffda9dbbfb739b23789a2f0e5056e8960acec387 /SRC/sstedc.f | |
| parent | 2491c9367a9c5e827a935679a4755387b348e159 (diff) | |
| download | lapack-6d3c6b3d719c4fa38f8321e398a8ab142c124f22.tar.gz lapack-6d3c6b3d719c4fa38f8321e398a8ab142c124f22.tar.bz2 lapack-6d3c6b3d719c4fa38f8321e398a8ab142c124f22.zip | |
Fix bug 139 submitted by Christoph Conrads on Oct 6th 2015
"according to the LAPACK documentation, xSTEDC guarantees to
return the eigenvalues in ascending order (parameter D on exit). To
this end, it sorts the eigenvalues if necessary.
If there is only a single subproblem of size n, no sorting algorithm is
called (cf. {s,d}tedc.f, line 450). Furthermore, xLAED0
({s,d}tedc.f:400) does not guarantee to return eigenvalues in ascending
order. Thus, xSTEDC may return eigenvalues that are not in ascending
order."
Applied patch provided by Christoph Conrads: "always sorting the eigenvalues"
Diffstat (limited to 'SRC/sstedc.f')
| -rw-r--r-- | SRC/sstedc.f | 50 |
1 files changed, 22 insertions, 28 deletions
diff --git a/SRC/sstedc.f b/SRC/sstedc.f index 841f7e45..f4e3d0b9 100644 --- a/SRC/sstedc.f +++ b/SRC/sstedc.f @@ -442,38 +442,32 @@ * * endwhile * -* If the problem split any number of times, then the eigenvalues -* will not be properly ordered. Here we permute the eigenvalues -* (and the associated eigenvectors) into ascending order. + IF( ICOMPZ.EQ.0 ) THEN * - IF( M.NE.N ) THEN - IF( ICOMPZ.EQ.0 ) THEN +* Use Quick Sort * -* Use Quick Sort + CALL SLASRT( 'I', N, D, INFO ) * - CALL SLASRT( 'I', N, D, INFO ) -* - ELSE + ELSE * -* Use Selection Sort to minimize swaps of eigenvectors -* - DO 40 II = 2, N - I = II - 1 - K = I - P = D( I ) - DO 30 J = II, N - IF( D( J ).LT.P ) THEN - K = J - P = D( J ) - END IF - 30 CONTINUE - IF( K.NE.I ) THEN - D( K ) = D( I ) - D( I ) = P - CALL SSWAP( N, Z( 1, I ), 1, Z( 1, K ), 1 ) - END IF - 40 CONTINUE - END IF +* Use Selection Sort to minimize swaps of eigenvectors +* + DO 40 II = 2, N + I = II - 1 + K = I + P = D( I ) + DO 30 J = II, N + IF( D( J ).LT.P ) THEN + K = J + P = D( J ) + END IF + 30 CONTINUE + IF( K.NE.I ) THEN + D( K ) = D( I ) + D( I ) = P + CALL SSWAP( N, Z( 1, I ), 1, Z( 1, K ), 1 ) + END IF + 40 CONTINUE END IF END IF * |