sgbbrd.f(3)

NAME
sgbbrd.f

SYNOPSIS

  Functions/Subroutines
subroutine sgbbrd (VECT, M, N, NCC, KL, KU, AB, LDAB, D, E, Q, LDQ, PT, LDPT, C, LDC, WORK, INFO)
SGBBRD

Function/Subroutine Documentation

  subroutine sgbbrd (character VECT, integer M, integer N, integer NCC, integer KL, integer KU, real, dimension( ldab, * ) AB, integer LDAB, real, dimension( * ) D, real, dimension( * ) E, real, dimension( ldq, * ) Q, integer LDQ, real, dimension( ldpt, * ) PT, integer LDPT, real, dimension( ldc, * ) C, integer LDC, real, dimension( * ) WORK, integer INFO)

Purpose:

     SGBBRD 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 REAL 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 REAL array, dimension (min(M,N))
              The diagonal elements of the bidiagonal matrix B.

    E

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

    Q

              Q is REAL 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 REAL 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 REAL 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 REAL 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.

Definition at line 185 of file sgbbrd.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.