dgbbrd.f (3) Linux Manual Page

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

 M is INTEGER

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

N

 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

 KL is INTEGER

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

KU

 KU is INTEGER

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

AB

 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

 D is DOUBLE PRECISION array, dimension (min(M,N))

 The diagonal elements of the bidiagonal matrix B.

E

 E is DOUBLE PRECISION array, dimension (min(M,N)-1)

 The superdiagonal elements of the bidiagonal matrix B.

Q

 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

 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

 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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