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

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.

Date:
    November 2011

Definition at line 187 of file sgbbrd.f.

Author

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