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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/cgebal.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/cgebal.f')
| -rw-r--r-- | SRC/cgebal.f | 16 |
1 files changed, 5 insertions, 11 deletions
diff --git a/SRC/cgebal.f b/SRC/cgebal.f index 4bb5a2f0..47207ea3 100644 --- a/SRC/cgebal.f +++ b/SRC/cgebal.f @@ -195,8 +195,8 @@ * .. External Functions .. LOGICAL SISNAN, LSAME INTEGER ICAMAX - REAL SLAMCH - EXTERNAL SISNAN, LSAME, ICAMAX, SLAMCH + REAL SLAMCH, SCNRM2 + EXTERNAL SISNAN, LSAME, ICAMAX, SLAMCH, SCNRM2 * .. * .. External Subroutines .. EXTERNAL CSSCAL, CSWAP, XERBLA @@ -325,15 +325,9 @@ 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 = SCNRM2( L-K+1, A( K, I ), 1 ) + R = SCNRM2( L-K+1, A( I , K ), LDA ) ICA = ICAMAX( L, A( 1, I ), 1 ) CA = ABS( A( ICA, I ) ) IRA = ICAMAX( N-K+1, A( I, K ), LDA ) |