dgbbrd-f(3)

dgbbrd.f –

Synopsis

Functions/Subroutines

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

Function/Subroutine Documentation

subroutine dgbbrd (characterVECT, integerM, integerN, integerNCC, integerKL, integerKU, double precision, dimension( ldab, * )AB, integerLDAB, double precision, dimension( * )D, double precision, dimension( * )E, double precision, dimension( ldq, * )Q, integerLDQ, double precision, dimension( ldpt, * )PT, integerLDPT, double precision, dimension( ldc, * )C, integerLDC, double precision, dimension( * )WORK, integerINFO)

DGBBRD

Purpose:

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

Parameters:

VECT

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

 M is INTEGER
 The number of rows of the matrix A. M >= 0.

 N is INTEGER
 The number of columns of the matrix A. N >= 0.

NCC

 NCC is INTEGER
 The number of columns of the matrix C. NCC >= 0.

 KL is INTEGER
 The number of subdiagonals of the matrix A. KL >= 0.

 KU is INTEGER
 The number of superdiagonals of the matrix A. KU >= 0.

 AB is 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 generated during the
 reduction.

LDAB

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

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

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

 Q is 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

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

 PT is 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

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

 C is DOUBLE PRECISION array, dimension (LDC,NCC)
 On entry, an m-by-ncc matrix C.
 On exit, C is overwritten by Q**T*C.
 C is not referenced if NCC = 0.

LDC

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

WORK

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

INFO

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

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 187 of file dgbbrd.f.

Author

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