dlaqz1()

subroutine dlaqz1	(	double precision, dimension( lda, * ), intent(in)	a,
		integer, intent(in)	lda,
		double precision, dimension( ldb, * ), intent(in)	b,
		integer, intent(in)	ldb,
		double precision, intent(in)	sr1,
		double precision, intent(in)	sr2,
		double precision, intent(in)	si,
		double precision, intent(in)	beta1,
		double precision, intent(in)	beta2,
		double precision, dimension( * ), intent(out)	v )

DLAQZ1

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Purpose:

!>
!>      Given a 3-by-3 matrix pencil (A,B), DLAQZ1 sets v to a
!>      scalar multiple of the first column of the product
!>
!>      (*)  K = (A - (beta2*sr2 - i*si)*B)*B^(-1)*(beta1*A - (sr2 + i*si2)*B)*B^(-1).
!>
!>      It is assumed that either
!>
!>              1) sr1 = sr2
!>          or
!>              2) si = 0.
!>
!>      This is useful for starting double implicit shift bulges
!>      in the QZ algorithm.
!> 

Parameters

[in]	A	!> A is DOUBLE PRECISION array, dimension (LDA,N) !> The 3-by-3 matrix A in (*). !>
[in]	LDA	!> LDA is INTEGER !> The leading dimension of A as declared in !> the calling procedure. !>
[in]	B	!> B is DOUBLE PRECISION array, dimension (LDB,N) !> The 3-by-3 matrix B in (*). !>
[in]	LDB	!> LDB is INTEGER !> The leading dimension of B as declared in !> the calling procedure. !>
[in]	SR1	!> SR1 is DOUBLE PRECISION !>
[in]	SR2	!> SR2 is DOUBLE PRECISION !>
[in]	SI	!> SI is DOUBLE PRECISION !>
[in]	BETA1	!> BETA1 is DOUBLE PRECISION !>
[in]	BETA2	!> BETA2 is DOUBLE PRECISION !>
[out]	V	!> V is DOUBLE PRECISION array, dimension (N) !> A scalar multiple of the first column of the !> matrix K in (*). !>

Author

Thijs Steel, KU Leuven

Date

May 2020