LAQZ2 - 5.2 English - 68552

LAQZ2 chases a 2x2 shift bulge in a matrix pencil down a single position.

Purpose:

 LAQZ2 chases a 2x2 shift bulge in a matrix pencil down a single position

Parameters:

• ILQ – [in]

  ILQ is LOGICAL

  Determines whether or not to update the matrix Q

• ILZ – [in]

  ILZ is LOGICAL

  Determines whether or not to update the matrix Z

• K – [in]

  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 – [in] ISTARTM is INTEGER

• ISTOPM – [in]

  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 – [in] IHI is INTEGER

• A – [inout] A is REAL array, dimension (LDA,N)

• LDA – [in]

  LDA is INTEGER

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

• B – [inout] B is REAL array, dimension (LDB,N)

• LDB – [in]

  LDB is INTEGER

  The leading dimension of B as declared in the calling procedure.

• NQ – [in]

  NQ is INTEGER

  The order of the matrix Q

• QSTART – [in]

  QSTART is INTEGER

  Start index of the matrix Q. Rotations are applied To columns k+2-qStart:k+4-qStart of Q.

• Q – [inout] Q is REAL array, dimension (LDQ,NQ)

• LDQ – [in]

  LDQ is INTEGER

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

• NZ – [in]

  NZ is INTEGER

  The order of the matrix Z

• ZSTART – [in]

  ZSTART is INTEGER

  Start index of the matrix Z. Rotations are applied To columns k+1-qStart:k+3-qStart of Z.

• Z – [inout] Z is REAL array, dimension (LDZ,NZ)

• LDZ – [in]

  LDZ is INTEGER

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