Contents
dgbbrd - reduce a real general m-by-n band matrix A to upper
bidiagonal form B by an orthogonal transformation
SUBROUTINE DGBBRD(VECT, M, N, NCC, KL, KU, AB, LDAB, D, E, Q, LDQ,
PT, LDPT, C, LDC, WORK, INFO)
CHARACTER * 1 VECT
INTEGER M, N, NCC, KL, KU, LDAB, LDQ, LDPT, LDC, INFO
DOUBLE PRECISION AB(LDAB,*), D(*), E(*), Q(LDQ,*),
PT(LDPT,*), C(LDC,*), WORK(*)
SUBROUTINE DGBBRD_64(VECT, M, N, NCC, KL, KU, AB, LDAB, D, E, Q, LDQ,
PT, LDPT, C, LDC, WORK, INFO)
CHARACTER * 1 VECT
INTEGER*8 M, N, NCC, KL, KU, LDAB, LDQ, LDPT, LDC, INFO
DOUBLE PRECISION AB(LDAB,*), D(*), E(*), Q(LDQ,*),
PT(LDPT,*), C(LDC,*), WORK(*)
F95 INTERFACE
SUBROUTINE GBBRD(VECT, M, [N], [NCC], KL, KU, AB, [LDAB], D, E, Q,
[LDQ], PT, [LDPT], C, [LDC], [WORK], [INFO])
CHARACTER(LEN=1) :: VECT
INTEGER :: M, N, NCC, KL, KU, LDAB, LDQ, LDPT, LDC, INFO
REAL(8), DIMENSION(:) :: D, E, WORK
REAL(8), DIMENSION(:,:) :: AB, Q, PT, C
SUBROUTINE GBBRD_64(VECT, M, [N], [NCC], KL, KU, AB, [LDAB], D, E,
Q, [LDQ], PT, [LDPT], C, [LDC], [WORK], [INFO])
CHARACTER(LEN=1) :: VECT
INTEGER(8) :: M, N, NCC, KL, KU, LDAB, LDQ, LDPT, LDC, INFO
REAL(8), DIMENSION(:) :: D, E, WORK
REAL(8), DIMENSION(:,:) :: AB, Q, PT, C
C INTERFACE
#include <sunperf.h>
void dgbbrd(char vect, int m, int n, int ncc, int kl, int
ku, double *ab, int ldab, double *d, double *e,
double *q, int ldq, double *pt, int ldpt, double
*c, int ldc, int *info);
void dgbbrd_64(char vect, long m, long n, long ncc, long kl,
long ku, double *ab, long ldab, double *d, double
*e, double *q, long ldq, double *pt, long ldpt,
double *c, long ldc, long *info);
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.
VECT (input)
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) The number of rows of the matrix A. M >= 0.
N (input) The number of columns of the matrix A. N >= 0.
NCC (input)
The number of columns of the matrix C. NCC >= 0.
KL (input)
The number of subdiagonals of the matrix A. KL >=
0.
KU (input)
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 generated during the reduction.
LDAB (input)
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)
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)
The leading dimension of the array PT. LDPT >=
max(1,N) if VECT = 'P' or 'B'; LDPT >= 1 other-
wise.
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 referenced if NCC =
0.
LDC (input)
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)
= 0: successful exit.
< 0: if INFO = -i, the i-th argument had an ille-
gal value.