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SGGHRD(3F)							    SGGHRD(3F)


NAME    [Toc]    [Back]

     SGGHRD - reduce 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

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	SGGHRD(	COMPQ, COMPZ, N, ILO, IHI, A, LDA, B, LDB, Q, LDQ, Z,
			LDZ, INFO )

	 CHARACTER	COMPQ, COMPZ

	 INTEGER	IHI, ILO, INFO,	LDA, LDB, LDQ, LDZ, N

	 REAL		A( LDA,	* ), B(	LDB, * ), Q( LDQ, * ), Z( LDZ, * )

PURPOSE    [Toc]    [Back]

     SGGHRD 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    [Toc]    [Back]

     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 SGGBAL; 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.



									Page 1






SGGHRD(3F)							    SGGHRD(3F)



     A	     (input/output) REAL 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) REAL 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) REAL 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) REAL 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.)
SGGHRD(3F)							    SGGHRD(3F)


NAME    [Toc]    [Back]

     SGGHRD - reduce 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

SYNOPSIS    [Toc]    [Back]

     SUBROUTINE	SGGHRD(	COMPQ, COMPZ, N, ILO, IHI, A, LDA, B, LDB, Q, LDQ, Z,
			LDZ, INFO )

	 CHARACTER	COMPQ, COMPZ

	 INTEGER	IHI, ILO, INFO,	LDA, LDB, LDQ, LDZ, N

	 REAL		A( LDA,	* ), B(	LDB, * ), Q( LDQ, * ), Z( LDZ, * )

PURPOSE    [Toc]    [Back]

     SGGHRD 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    [Toc]    [Back]

     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 SGGBAL; 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.



									Page 1






SGGHRD(3F)							    SGGHRD(3F)



     A	     (input/output) REAL 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) REAL 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) REAL 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) REAL 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.)


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