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| author | Christoph Conrads <gitlab@christoph-conrads.name> | 2016-09-21 16:57:56 +0200 |
|---|---|---|
| committer | Christoph Conrads <gitlab@christoph-conrads.name> | 2016-09-29 17:01:43 +0200 |
| commit | a27af559caf84acb0a77704dbca7fdc4cb356a2f (patch) | |
| tree | c81280b3ae7a80fdfb4d8f749e281d4d83bf8ad2 /SRC/cpoequb.f | |
| parent | c100a3c6654936d989b0f5138285bbeda4094c62 (diff) | |
| download | lapack-a27af559caf84acb0a77704dbca7fdc4cb356a2f.tar.gz lapack-a27af559caf84acb0a77704dbca7fdc4cb356a2f.tar.bz2 lapack-a27af559caf84acb0a77704dbca7fdc4cb356a2f.zip | |
Doc: improve xPOEQUB description
- highlight difference to xPOEQU
- replace "symmetric" with "Hermitian" for {c,z}POEQUB
Diffstat (limited to 'SRC/cpoequb.f')
| -rw-r--r-- | SRC/cpoequb.f | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/SRC/cpoequb.f b/SRC/cpoequb.f index e0f47420..53320ee4 100644 --- a/SRC/cpoequb.f +++ b/SRC/cpoequb.f @@ -36,13 +36,19 @@ *> \verbatim *> *> CPOEQUB computes row and column scalings intended to equilibrate a -*> symmetric positive definite matrix A and reduce its condition number +*> Hermitian positive definite matrix A and reduce its condition number *> (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. +*> +*> This routine differs from CPOEQU by restricting the scaling factors +*> to a power of the radix. Barring over- and underflow, scaling by +*> these factors introduces no additional rounding errors. However, the +*> scaled diagonal entries are no longer approximately 1 but lie +*> between sqrt(radix) and 1/sqrt(radix). *> \endverbatim * * Arguments: @@ -57,7 +63,7 @@ *> \param[in] A *> \verbatim *> A is COMPLEX array, dimension (LDA,N) -*> The N-by-N symmetric positive definite matrix whose scaling +*> The N-by-N Hermitian positive definite matrix whose scaling *> factors are to be computed. Only the diagonal elements of A *> are referenced. *> \endverbatim |