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| author | james <james@8a072113-8704-0410-8d35-dd094bca7971> | 2013-05-16 18:55:48 +0000 |
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| committer | james <james@8a072113-8704-0410-8d35-dd094bca7971> | 2013-05-16 18:55:48 +0000 |
| commit | 78de161a101e23236d6804b7e7f9ba66845d9586 (patch) | |
| tree | aeb29d27f46e3727620cddb723b9e6b9ddc07ba6 /SRC/zgebal.f | |
| parent | 0dbca9069031ea055e3c54fcb72087fe48a290ab (diff) | |
| download | lapack-78de161a101e23236d6804b7e7f9ba66845d9586.tar.gz lapack-78de161a101e23236d6804b7e7f9ba66845d9586.tar.bz2 lapack-78de161a101e23236d6804b7e7f9ba66845d9586.zip | |
Now using 2-norm to compute vector norms of row and column for balancing algorithm.
This seems to fix problems with balancing causing very large backward error for certain
Hessenberg matrices, including the often cited example of Watkins.
Diffstat (limited to 'SRC/zgebal.f')
| -rw-r--r-- | SRC/zgebal.f | 16 |
1 files changed, 5 insertions, 11 deletions
diff --git a/SRC/zgebal.f b/SRC/zgebal.f index 9c90f0b4..aa4f6d0e 100644 --- a/SRC/zgebal.f +++ b/SRC/zgebal.f @@ -194,8 +194,8 @@ * .. External Functions .. LOGICAL DISNAN, LSAME INTEGER IZAMAX - DOUBLE PRECISION DLAMCH - EXTERNAL DISNAN, LSAME, IZAMAX, DLAMCH + DOUBLE PRECISION DLAMCH, DZNRM2 + EXTERNAL DISNAN, LSAME, IZAMAX, DLAMCH, DZNRM2 * .. * .. External Subroutines .. EXTERNAL XERBLA, ZDSCAL, ZSWAP @@ -324,15 +324,9 @@ NOCONV = .FALSE. * DO 200 I = K, L - C = ZERO - R = ZERO -* - DO 150 J = K, L - IF( J.EQ.I ) - $ GO TO 150 - C = C + CABS1( A( J, I ) ) - R = R + CABS1( A( I, J ) ) - 150 CONTINUE +* + C = DZNRM2( L-K+1, A( K, I ), 1 ) + R = DZNRM2( L-K+1, A( I, K ), LDA ) ICA = IZAMAX( L, A( 1, I ), 1 ) CA = ABS( A( ICA, I ) ) IRA = IZAMAX( N-K+1, A( I, K ), LDA ) |