LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ dlaqz2()

subroutine dlaqz2 ( logical, intent(in) ilq,
logical, intent(in) ilz,
integer, intent(in) k,
integer, intent(in) istartm,
integer, intent(in) istopm,
integer, intent(in) ihi,
double precision, dimension( lda, * ) a,
integer, intent(in) lda,
double precision, dimension( ldb, * ) b,
integer, intent(in) ldb,
integer, intent(in) nq,
integer, intent(in) qstart,
double precision, dimension( ldq, * ) q,
integer, intent(in) ldq,
integer, intent(in) nz,
integer, intent(in) zstart,
double precision, dimension( ldz, * ) z,
integer, intent(in) ldz )

DLAQZ2

Download DLAQZ2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
!>
!>      DLAQZ2 chases a 2x2 shift bulge in a matrix pencil down a single position
!>
Parameters
[in]ILQ
!>          ILQ is LOGICAL
!>              Determines whether or not to update the matrix Q
!>
[in]ILZ
!>          ILZ is LOGICAL
!>              Determines whether or not to update the matrix Z
!>
[in]K
!>          K is INTEGER
!>              Index indicating the position of the bulge.
!>              On entry, the bulge is located in
!>              (A(k+1:k+2,k:k+1),B(k+1:k+2,k:k+1)).
!>              On exit, the bulge is located in
!>              (A(k+2:k+3,k+1:k+2),B(k+2:k+3,k+1:k+2)).
!>
[in]ISTARTM
!>          ISTARTM is INTEGER
!>
[in]ISTOPM
!>          ISTOPM is INTEGER
!>              Updates to (A,B) are restricted to
!>              (istartm:k+3,k:istopm). It is assumed
!>              without checking that istartm <= k+1 and
!>              k+2 <= istopm
!>
[in]IHI
!>          IHI is INTEGER
!>
[in,out]A
!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>
[in]LDA
!>          LDA is INTEGER
!>              The leading dimension of A as declared in
!>              the calling procedure.
!>
[in,out]B
!>          B is DOUBLE PRECISION array, dimension (LDB,N)
!>
[in]LDB
!>          LDB is INTEGER
!>              The leading dimension of B as declared in
!>              the calling procedure.
!>
[in]NQ
!>          NQ is INTEGER
!>              The order of the matrix Q
!>
[in]QSTART
!>          QSTART is INTEGER
!>              Start index of the matrix Q. Rotations are applied
!>              To columns k+2-qStart:k+4-qStart of Q.
!>
[in,out]Q
!>          Q is DOUBLE PRECISION array, dimension (LDQ,NQ)
!>
[in]LDQ
!>          LDQ is INTEGER
!>              The leading dimension of Q as declared in
!>              the calling procedure.
!>
[in]NZ
!>          NZ is INTEGER
!>              The order of the matrix Z
!>
[in]ZSTART
!>          ZSTART is INTEGER
!>              Start index of the matrix Z. Rotations are applied
!>              To columns k+1-qStart:k+3-qStart of Z.
!>
[in,out]Z
!>          Z is DOUBLE PRECISION array, dimension (LDZ,NZ)
!>
[in]LDZ
!>          LDZ is INTEGER
!>              The leading dimension of Q as declared in
!>              the calling procedure.
!>
Author
Thijs Steel, KU Leuven
Date
May 2020