NAME

SRC/dlaqz1.f

SYNOPSIS

Functions/Subroutines

subroutine dlaqz1 (a, lda, b, ldb, sr1, sr2, si, beta1, beta2, v)
DLAQZ1

Function/Subroutine Documentation

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

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

          A is DOUBLE PRECISION array, dimension (LDA,N)
              The 3-by-3 matrix A in (*).

LDA

          LDA is INTEGER
              The leading dimension of A as declared in
              the calling procedure.

          B is DOUBLE PRECISION array, dimension (LDB,N)
              The 3-by-3 matrix B in (*).

LDB

          LDB is INTEGER
              The leading dimension of B as declared in
              the calling procedure.

SR1

          SR1 is DOUBLE PRECISION

SR2

          SR2 is DOUBLE PRECISION

          SI is DOUBLE PRECISION

BETA1

          BETA1 is DOUBLE PRECISION

BETA2

          BETA2 is DOUBLE PRECISION

          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

Definition at line 125 of file dlaqz1.f.

Author

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