dsvdct3
Part of dsvdct.f(3).
Usage
Functions/Subroutines
DSVDCT
Function/Subroutine Documentation
subroutine dsvdct (integer n, double precision, dimension( * ) s, double precision, dimension( * ) e, double precision shift, integer num)
DSVDCT
Purpose:
!> !> DSVDCT counts the number NUM of eigenvalues of a 2*N by 2*N !> tridiagonal matrix T which are less than or equal to SHIFT. T is !> formed by putting zeros on the diagonal and making the off-diagonals !> equal to S(1), E(1), S(2), E(2), ... , E(N-1), S(N). If SHIFT is !> positive, NUM is equal to N plus the number of singular values of a !> bidiagonal matrix B less than or equal to SHIFT. Here B has diagonal !> entries S(1), ..., S(N) and superdiagonal entries E(1), ... E(N-1). !> If SHIFT is negative, NUM is equal to the number of singular values !> of B greater than or equal to -SHIFT. !> !> See W. Kahan , Report CS41, Computer Science Dept., Stanford University, !> July 21, 1966 !>
Parameters
N
!> N is INTEGER !> The dimension of the bidiagonal matrix B. !>
S
!> S is DOUBLE PRECISION array, dimension (N) !> The diagonal entries of the bidiagonal matrix B. !>
E
!> E is DOUBLE PRECISION array of dimension (N-1) !> The superdiagonal entries of the bidiagonal matrix B. !>
SHIFT
!> SHIFT is DOUBLE PRECISION !> The shift, used as described under Purpose. !>
NUM
!> NUM is INTEGER !> The number of eigenvalues of T less than or equal to SHIFT. !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 86 of file dsvdct.f.