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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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| subroutine dsyequb | ( | character | UPLO, |
| integer | N, | ||
| double precision, dimension( lda, * ) | A, | ||
| integer | LDA, | ||
| double precision, dimension( * ) | S, | ||
| double precision | SCOND, | ||
| double precision | AMAX, | ||
| double precision, dimension( * ) | WORK, | ||
| integer | INFO | ||
| ) |
DSYEQUB
Download DSYEQUB + dependencies [TGZ] [ZIP] [TXT]
DSYEQUB computes row and column scalings intended to equilibrate a symmetric matrix A (with respect to the Euclidean norm) and reduce its condition number. The scale factors S are computed by the BIN algorithm (see references) so that the scaled matrix B with elements B(i,j) = S(i)*A(i,j)*S(j) has a condition number within a factor N of the smallest possible condition number over all possible diagonal scalings.
| [in] | UPLO | UPLO is CHARACTER*1
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored. |
| [in] | N | N is INTEGER
The order of the matrix A. N >= 0. |
| [in] | A | A is DOUBLE PRECISION array, dimension (LDA,N)
The N-by-N symmetric matrix whose scaling factors are to be
computed. |
| [in] | LDA | LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,N). |
| [out] | S | S is DOUBLE PRECISION array, dimension (N)
If INFO = 0, S contains the scale factors for A. |
| [out] | SCOND | SCOND is DOUBLE PRECISION
If INFO = 0, S contains the ratio of the smallest S(i) to
the largest S(i). If SCOND >= 0.1 and AMAX is neither too
large nor too small, it is not worth scaling by S. |
| [out] | AMAX | AMAX is DOUBLE PRECISION
Largest absolute value of any matrix element. If AMAX is
very close to overflow or very close to underflow, the
matrix should be scaled. |
| [out] | WORK | WORK is DOUBLE PRECISION array, dimension (2*N) |
| [out] | INFO | INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the i-th diagonal element is nonpositive. |
1.9.4