LAPACK 3.11.0
LAPACK: Linear Algebra PACKage

◆ 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

Download DLAQZ1 + dependencies [TGZ] [ZIP] [TXT]

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