table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zppequ.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zppequ.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/zppequ.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine ZPPEQU (uplo, n, ap, s, scond, amax, info)
ZPPEQU
Function/Subroutine Documentation¶
subroutine ZPPEQU (character uplo, integer n, complex*16, dimension( * ) ap, double precision, dimension( * ) s, double precision scond, double precision amax, integer info)¶
ZPPEQU
Purpose:
!> !> ZPPEQU computes row and column scalings intended to equilibrate a !> Hermitian positive definite matrix A in packed storage 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. !>
Parameters
UPLO
!> UPLO is CHARACTER*1 !> = 'U': Upper triangle of A is stored; !> = 'L': Lower triangle of A is stored. !>
N
!> N is INTEGER !> The order of the matrix A. N >= 0. !>
AP
!> AP is COMPLEX*16 array, dimension (N*(N+1)/2) !> 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. !>
S
!> S is DOUBLE PRECISION array, dimension (N) !> If INFO = 0, S contains the scale factors for A. !>
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. !>
AMAX
!> AMAX is DOUBLE PRECISION !> Absolute value of largest matrix element. If AMAX is very !> close to overflow or very close to underflow, the matrix !> should be scaled. !>
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. !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 116 of file zppequ.f.
Author¶
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Version 3.12.0 | LAPACK |