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| author | Christoph Conrads <gitlab@christoph-conrads.name> | 2016-09-21 16:08:23 +0200 |
|---|---|---|
| committer | Christoph Conrads <gitlab@christoph-conrads.name> | 2016-09-29 17:01:43 +0200 |
| commit | 4958a3718bd37740abbf2e831821158b5de935bd (patch) | |
| tree | 1fe370b8190c08eb05a68e7d97a5fdf2f859daa0 /SRC/cpoequb.f | |
| parent | ac521225cda428797b67bd4004048d1d2817edd9 (diff) | |
| download | lapack-4958a3718bd37740abbf2e831821158b5de935bd.tar.gz lapack-4958a3718bd37740abbf2e831821158b5de935bd.tar.bz2 lapack-4958a3718bd37740abbf2e831821158b5de935bd.zip | |
Revert "Doc: highlight what xPOEQUB actually does"
This reverts commit 3c66ad2c7d6e2e73e369dbd919bba259b42e2f6d.
Diffstat (limited to 'SRC/cpoequb.f')
| -rw-r--r-- | SRC/cpoequb.f | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/SRC/cpoequb.f b/SRC/cpoequb.f index bf86d1a4..e0f47420 100644 --- a/SRC/cpoequb.f +++ b/SRC/cpoequb.f @@ -37,12 +37,12 @@ *> *> CPOEQUB computes row and column scalings intended to equilibrate a *> symmetric positive definite matrix A and reduce its condition number -*> (with respect to the spectral norm). S contains the scale factors, -*> chosen so that the scaled matrix B with elements -*> B(i,j) = S(i)*A(i,j)*S(j) has diagonal entries close to one. S(i) is -*> a power of b nearest to but not exceeding 1/sqrt(A(i,i)), where b is -*> the basis use for floating point numbers on this machine. This choice -*> of S avoids round-off errors when computing B. +*> (with respect to the two-norm). S contains the scale factors, +*> S(i) = 1/sqrt(A(i,i)), chosen so that the scaled matrix B with +*> elements B(i,j) = S(i)*A(i,j)*S(j) has ones on the diagonal. This +*> choice of S puts the condition number of B within a factor N of the +*> smallest possible condition number over all possible diagonal +*> scalings. *> \endverbatim * * Arguments: @@ -151,6 +151,8 @@ * * Test the input parameters. * +* Positive definite only performs 1 pass of equilibration. +* INFO = 0 IF( N.LT.0 ) THEN INFO = -1 |