DLAQZ2 chases a 2x2 shift bulge in a matrix pencil down a single position

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 DOUBLE PRECISION array, dimension (LDA,N)

LDA

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

B

          B is DOUBLE PRECISION 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 DOUBLE PRECISION 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 DOUBLE PRECISION array, dimension (LDZ,NZ)

LDZ

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

Thijs Steel, KU Leuven

May 2020