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RedHat 9 (Linux i386) - man page for dgbbrd (redhat section l)

DGBBRD(l)					)					DGBBRD(l)

NAME
       DGBBRD  -  reduce  a  real  general  m-by-n band matrix A to upper bidiagonal form B by an
       orthogonal transformation

SYNOPSIS
       SUBROUTINE DGBBRD( VECT, M, N, NCC, KL, KU, AB, LDAB, D, E, Q,  LDQ,  PT,  LDPT,  C,  LDC,
			  WORK, INFO )

	   CHARACTER	  VECT

	   INTEGER	  INFO, KL, KU, LDAB, LDC, LDPT, LDQ, M, N, NCC

	   DOUBLE	  PRECISION AB( LDAB, * ), C( LDC, * ), D( * ), E( * ), PT( LDPT, * ), Q(
			  LDQ, * ), WORK( * )

PURPOSE
       DGBBRD reduces a real general m-by-n band matrix A  to  upper  bidiagonal  form	B  by  an
       orthogonal transformation: Q' * A * P = B.  The routine computes B, and optionally forms Q
       or P', or computes Q'*C for a given matrix C.

ARGUMENTS
       VECT    (input) CHARACTER*1
	       Specifies whether or not the matrices Q and P' are to be formed.  =  'N':  do  not
	       form Q or P';
	       = 'Q': form Q only;
	       = 'P': form P' only;
	       = 'B': form both.

       M       (input) INTEGER
	       The number of rows of the matrix A.  M >= 0.

       N       (input) INTEGER
	       The number of columns of the matrix A.  N >= 0.

       NCC     (input) INTEGER
	       The number of columns of the matrix C.  NCC >= 0.

       KL      (input) INTEGER
	       The number of subdiagonals of the matrix A. KL >= 0.

       KU      (input) INTEGER
	       The number of superdiagonals of the matrix A. KU >= 0.

       AB      (input/output) DOUBLE PRECISION array, dimension (LDAB,N)
	       On  entry,  the m-by-n band matrix A, stored in rows 1 to KL+KU+1. The j-th column
	       of A is stored in the j-th column of the array AB  as  follows:	AB(ku+1+i-j,j)	=
	       A(i,j)  for max(1,j-ku)<=i<=min(m,j+kl).  On exit, A is overwritten by values gen-
	       erated during the reduction.

       LDAB    (input) INTEGER
	       The leading dimension of the array A. LDAB >= KL+KU+1.

       D       (output) DOUBLE PRECISION array, dimension (min(M,N))
	       The diagonal elements of the bidiagonal matrix B.

       E       (output) DOUBLE PRECISION array, dimension (min(M,N)-1)
	       The superdiagonal elements of the bidiagonal matrix B.

       Q       (output) DOUBLE PRECISION array, dimension (LDQ,M)
	       If VECT = 'Q' or 'B', the m-by-m orthogonal matrix Q.  If VECT = 'N' or	'P',  the
	       array Q is not referenced.

       LDQ     (input) INTEGER
	       The  leading  dimension of the array Q.	LDQ >= max(1,M) if VECT = 'Q' or 'B'; LDQ
	       >= 1 otherwise.

       PT      (output) DOUBLE PRECISION array, dimension (LDPT,N)
	       If VECT = 'P' or 'B', the n-by-n orthogonal matrix P'.  If VECT = 'N' or 'Q',  the
	       array PT is not referenced.

       LDPT    (input) INTEGER
	       The  leading  dimension	of  the array PT.  LDPT >= max(1,N) if VECT = 'P' or 'B';
	       LDPT >= 1 otherwise.

       C       (input/output) DOUBLE PRECISION array, dimension (LDC,NCC)
	       On entry, an m-by-ncc matrix C.	On exit, C is overwritten by Q'*C.  C is not ref-
	       erenced if NCC = 0.

       LDC     (input) INTEGER
	       The leading dimension of the array C.  LDC >= max(1,M) if NCC > 0; LDC >= 1 if NCC
	       = 0.

       WORK    (workspace) DOUBLE PRECISION array, dimension (2*max(M,N))

       INFO    (output) INTEGER
	       = 0:  successful exit.
	       < 0:  if INFO = -i, the i-th argument had an illegal value.

LAPACK version 3.0			   15 June 2000 				DGBBRD(l)


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