slaqz2.f(3)

NAME
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)

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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