org.netlib.lapack
Class Dgghrd

java.lang.Object
  org.netlib.lapack.Dgghrd

public class Dgghrd
extends java.lang.Object

Following is the description from the original
Fortran source.  For each array argument, the Java
version will include an integer offset parameter, so
the arguments may not match the description exactly.
Contact seymour@cs.utk.edu with any questions.


 *     ..
 *
 *  Purpose
 *  =======
 *
 *  DGGHRD reduces a pair of real matrices (A,B) to generalized upper
 *  Hessenberg form using orthogonal transformations, where A is a
 *  general matrix and B is upper triangular:  Q' * A * Z = H and
 *  Q' * B * Z = T, where H is upper Hessenberg, T is upper triangular,
 *  and Q and Z are orthogonal, and ' means transpose.
 *
 *  The orthogonal matrices Q and Z are determined as products of Givens

 *  rotations.  They may either be formed explicitly, or they may be
 *  postmultiplied into input matrices Q1 and Z1, so that
 *
 *       Q1 * A * Z1' = (Q1*Q) * H * (Z1*Z)'
 *       Q1 * B * Z1' = (Q1*Q) * T * (Z1*Z)'
 *
 *  Arguments
 *  =========
 *
 *  COMPQ   (input) CHARACTER*1
 *          = 'N': do not compute Q;
 *          = 'I': Q is initialized to the unit matrix, and the
 *                 orthogonal matrix Q is returned;
 *          = 'V': Q must contain an orthogonal matrix Q1 on entry,
 *                 and the product Q1*Q is returned.
 *
 *  COMPZ   (input) CHARACTER*1
 *          = 'N': do not compute Z;
 *          = 'I': Z is initialized to the unit matrix, and the
 *                 orthogonal matrix Z is returned;
 *          = 'V': Z must contain an orthogonal matrix Z1 on entry,
 *                 and the product Z1*Z is returned.
 *
 *  N       (input) INTEGER
 *          The order of the matrices A and B.  N >= 0.
 *
 *  ILO     (input) INTEGER
 *  IHI     (input) INTEGER
 *          It is assumed that A is already upper triangular in rows and

 *          columns 1:ILO-1 and IHI+1:N.  ILO and IHI are normally set
 *          by a previous call to DGGBAL; otherwise they should be set
 *          to 1 and N respectively.
 *          1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
 *
 *  A       (input/output) DOUBLE PRECISION array, dimension (LDA, N)
 *          On entry, the N-by-N general matrix to be reduced.
 *          On exit, the upper triangle and the first subdiagonal of A
 *          are overwritten with the upper Hessenberg matrix H, and the
 *          rest is set to zero.
 *
 *  LDA     (input) INTEGER
 *          The leading dimension of the array A.  LDA >= max(1,N).
 *
 *  B       (input/output) DOUBLE PRECISION array, dimension (LDB, N)
 *          On entry, the N-by-N upper triangular matrix B.
 *          On exit, the upper triangular matrix T = Q' B Z.  The
 *          elements below the diagonal are set to zero.
 *
 *  LDB     (input) INTEGER
 *          The leading dimension of the array B.  LDB >= max(1,N).
 *
 *  Q       (input/output) DOUBLE PRECISION array, dimension (LDQ, N)
 *          If COMPQ='N':  Q is not referenced.
 *          If COMPQ='I':  on entry, Q need not be set, and on exit it
 *                         contains the orthogonal matrix Q, where Q'
 *                         is the product of the Givens transformations
 *                         which are applied to A and B on the left.
 *          If COMPQ='V':  on entry, Q must contain an orthogonal matrix

 *                         Q1, and on exit this is overwritten by Q1*Q.
 *
 *  LDQ     (input) INTEGER
 *          The leading dimension of the array Q.
 *          LDQ >= N if COMPQ='V' or 'I'; LDQ >= 1 otherwise.
 *
 *  Z       (input/output) DOUBLE PRECISION array, dimension (LDZ, N)
 *          If COMPZ='N':  Z is not referenced.
 *          If COMPZ='I':  on entry, Z need not be set, and on exit it
 *                         contains the orthogonal matrix Z, which is
 *                         the product of the Givens transformations
 *                         which are applied to A and B on the right.
 *          If COMPZ='V':  on entry, Z must contain an orthogonal matrix

 *                         Z1, and on exit this is overwritten by Z1*Z.
 *
 *  LDZ     (input) INTEGER
 *          The leading dimension of the array Z.
 *          LDZ >= N if COMPZ='V' or 'I'; LDZ >= 1 otherwise.
 *
 *  INFO    (output) INTEGER
 *          = 0:  successful exit.
 *          < 0:  if INFO = -i, the i-th argument had an illegal value.
 *
 *  Further Details
 *  ===============
 *
 *  This routine reduces A to Hessenberg and B to triangular form by
 *  an unblocked reduction, as described in _Matrix_Computations_,
 *  by Golub and Van Loan (Johns Hopkins Press.)
 *
 *  =====================================================================
 *
 *     .. Parameters ..

Constructor Summary

Dgghrd()

Method Summary

static void

dgghrd(java.lang.String compq, java.lang.String compz, int n, int ilo, int ihi, double[] a, int _a_offset, int lda, double[] b, int _b_offset, int ldb, double[] q, int _q_offset, int ldq, double[] z, int _z_offset, int ldz, intW info)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Dgghrd

public Dgghrd()

Method Detail

dgghrd

public static void dgghrd(java.lang.String compq,
                          java.lang.String compz,
                          int n,
                          int ilo,
                          int ihi,
                          double[] a,
                          int _a_offset,
                          int lda,
                          double[] b,
                          int _b_offset,
                          int ldb,
                          double[] q,
                          int _q_offset,
                          int ldq,
                          double[] z,
                          int _z_offset,
                          int ldz,
                          intW info)