LAPACK 3.11.0
LAPACK: Linear Algebra PACKage

◆ slaqz2()

subroutine slaqz2 ( logical, intent(in)  ILQ,
logical, intent(in)  ILZ,
integer, intent(in)  K,
integer, intent(in)  ISTARTM,
integer, intent(in)  ISTOPM,
integer, intent(in)  IHI,
real, dimension( lda, * )  A,
integer, intent(in)  LDA,
real, dimension( ldb, * )  B,
integer, intent(in)  LDB,
integer, intent(in)  NQ,
integer, intent(in)  QSTART,
real, dimension( ldq, * )  Q,
integer, intent(in)  LDQ,
integer, intent(in)  NZ,
integer, intent(in)  ZSTART,
real, dimension( ldz, * )  Z,
integer, intent(in)  LDZ 
)

SLAQZ2

Download SLAQZ2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
      SLAQZ2 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 REAL 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 REAL 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 REAL 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 REAL 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