CLAQHP(l) ) CLAQHP(l)
CLAQHP - equilibrate a Hermitian matrix A using the scaling factors in the vector S
SUBROUTINE CLAQHP( UPLO, N, AP, S, SCOND, AMAX, EQUED )
CHARACTER EQUED, UPLO
REAL AMAX, SCOND
REAL S( * )
COMPLEX AP( * )
CLAQHP equilibrates a Hermitian matrix A using the scaling factors in the vector S.
UPLO (input) CHARACTER*1
Specifies whether the upper or lower triangular part of the Hermitian matrix A is
stored. = 'U': Upper triangular
= 'L': Lower triangular
N (input) INTEGER
The order of the matrix A. N >= 0.
AP (input/output) COMPLEX array, dimension (N*(N+1)/2)
On entry, the upper or lower triangle of the Hermitian matrix A, packed columnwise
in a linear array. The j-th column of A is stored in the array AP as follows: if
UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i +
(j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
On exit, the equilibrated matrix: diag(S) * A * diag(S), in the same storage for-
mat as A.
S (input) REAL array, dimension (N)
The scale factors for A.
SCOND (input) REAL
Ratio of the smallest S(i) to the largest S(i).
AMAX (input) REAL
Absolute value of largest matrix entry.
EQUED (output) CHARACTER*1
Specifies whether or not equilibration was done. = 'N': No equilibration.
= 'Y': Equilibration was done, i.e., A has been replaced by diag(S) * A *
THRESH is a threshold value used to decide if scaling should be done based on the ratio of
the scaling factors. If SCOND < THRESH, scaling is done.
LARGE and SMALL are threshold values used to decide if scaling should be done based on the
absolute size of the largest matrix element. If AMAX > LARGE or AMAX < SMALL, scaling is
LAPACK version 3.0 15 June 2000 CLAQHP(l)