TESTING/EIG/dbdt03.f(3)    Library Functions Manual    TESTING/EIG/dbdt03.f(3)

NAME
       TESTING/EIG/dbdt03.f

SYNOPSIS
   Functions/Subroutines
       subroutine dbdt03 (uplo, n, kd, d, e, u, ldu, s, vt, ldvt, work, resid)
           DBDT03

Function/Subroutine Documentation
   subroutine dbdt03 (character uplo, integer n, integer kd, double precision,
       dimension( * ) d, double precision, dimension( * ) e, double precision,
       dimension( ldu, * ) u, integer ldu, double precision, dimension( * ) s,
       double precision, dimension( ldvt, * ) vt, integer ldvt, double
       precision, dimension( * ) work, double precision resid)
       DBDT03

       Purpose:


            DBDT03 reconstructs a bidiagonal matrix B from its SVD:
               S = U' * B * V
            where U and V are orthogonal matrices and S is diagonal.

            The test ratio to test the singular value decomposition is
               RESID = norm( B - U * S * VT ) / ( n * norm(B) * EPS )
            where VT = V' and EPS is the machine precision.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the matrix B is upper or lower bidiagonal.
                     = 'U':  Upper bidiagonal
                     = 'L':  Lower bidiagonal

           N

                     N is INTEGER
                     The order of the matrix B.

           KD

                     KD is INTEGER
                     The bandwidth of the bidiagonal matrix B.  If KD = 1, the
                     matrix B is bidiagonal, and if KD = 0, B is diagonal and E is
                     not referenced.  If KD is greater than 1, it is assumed to be
                     1, and if KD is less than 0, it is assumed to be 0.

           D

                     D is DOUBLE PRECISION array, dimension (N)
                     The n diagonal elements of the bidiagonal matrix B.

           E

                     E is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) superdiagonal elements of the bidiagonal matrix B
                     if UPLO = 'U', or the (n-1) subdiagonal elements of B if
                     UPLO = 'L'.

           U

                     U is DOUBLE PRECISION array, dimension (LDU,N)
                     The n by n orthogonal matrix U in the reduction B = U'*A*P.

           LDU

                     LDU is INTEGER
                     The leading dimension of the array U.  LDU >= max(1,N)

           S

                     S is DOUBLE PRECISION array, dimension (N)
                     The singular values from the SVD of B, sorted in decreasing
                     order.

           VT

                     VT is DOUBLE PRECISION array, dimension (LDVT,N)
                     The n by n orthogonal matrix V' in the reduction
                     B = U * S * V'.

           LDVT

                     LDVT is INTEGER
                     The leading dimension of the array VT.

           WORK

                     WORK is DOUBLE PRECISION array, dimension (2*N)

           RESID

                     RESID is DOUBLE PRECISION
                     The test ratio:  norm(B - U * S * V') / ( n * norm(A) * EPS )

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 133 of file dbdt03.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0         TESTING/EIG/dbdt03.f(3)