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