SRC/sgbbrd.f(3)

NAME
SRC/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)

SGBBRD

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

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