SRC/slaqz2.f(3)

NAME
SRC/slaqz2.f

SYNOPSIS

  Functions/Subroutines
subroutine slaqz2 (ilq, ilz, k, istartm, istopm, ihi, a, lda, b, ldb, nq, qstart, q, ldq, nz, zstart, z, ldz)
SLAQZ2

Function/Subroutine Documentation

  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

Purpose:

    !>
    !>      SLAQZ2 chases a 2x2 shift bulge in a matrix pencil down a single position
    !>

Parameters
    ILQ

    !>          ILQ is LOGICAL
    !>              Determines whether or not to update the matrix Q
    !>

    ILZ

    !>          ILZ is LOGICAL
    !>              Determines whether or not to update the matrix Z
    !>

    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)).
    !>

    ISTARTM

    !>          ISTARTM is INTEGER
    !>

    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
    !>

    IHI

    !>          IHI is INTEGER
    !>

    A

    !>          A is REAL array, dimension (LDA,N)
    !>

    LDA

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

    B

    !>          B is REAL array, dimension (LDB,N)
    !>

    LDB

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

    NQ

    !>          NQ is INTEGER
    !>              The order of the matrix Q
    !>

    QSTART

    !>          QSTART is INTEGER
    !>              Start index of the matrix Q. Rotations are applied
    !>              To columns k+2-qStart:k+4-qStart of Q.
    !>

    Q

    !>          Q is REAL array, dimension (LDQ,NQ)
    !>

    LDQ

    !>          LDQ is INTEGER
    !>              The leading dimension of Q as declared in
    !>              the calling procedure.
    !>

    NZ

    !>          NZ is INTEGER
    !>              The order of the matrix Z
    !>

    ZSTART

    !>          ZSTART is INTEGER
    !>              Start index of the matrix Z. Rotations are applied
    !>              To columns k+1-qStart:k+3-qStart of Z.
    !>

    Z

    !>          Z is REAL array, dimension (LDZ,NZ)
    !>

    LDZ

    !>          LDZ is INTEGER
    !>              The leading dimension of Q as declared in
    !>              the calling procedure.
    !>

Author
    Thijs Steel, KU Leuven

Date
    May 2020

Definition at line 171 of file slaqz2.f.

Author

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