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## 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