TESTING/EIG/dbdt04.f(3)    Library Functions Manual    TESTING/EIG/dbdt04.f(3)

NAME
       TESTING/EIG/dbdt04.f

SYNOPSIS
   Functions/Subroutines
       subroutine dbdt04 (uplo, n, d, e, s, ns, u, ldu, vt, ldvt, work, resid)
           DBDT04

Function/Subroutine Documentation
   subroutine dbdt04 (character uplo, integer n, double precision, dimension(
       * ) d, double precision, dimension( * ) e, double precision, dimension(
       * ) s, integer ns, double precision, dimension( ldu, * ) u, integer
       ldu, double precision, dimension( ldvt, * ) vt, integer ldvt, double
       precision, dimension( * ) work, double precision resid)
       DBDT04

       Purpose:


            DBDT04 reconstructs a bidiagonal matrix B from its (partial) 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( S - U' * B * V ) / ( 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.

           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'.

           S

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

           NS

                     NS is INTEGER
                     The number of singular values/vectors from the (partial)
                     SVD of B.

           U

                     U is DOUBLE PRECISION array, dimension (LDU,NS)
                     The n by ns orthogonal matrix U in S = U' * B * V.

           LDU

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

           VT

                     VT is DOUBLE PRECISION array, dimension (LDVT,N)
                     The n by ns orthogonal matrix V in S = U' * B * 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(S - U' * B * V) / ( n * norm(B) * EPS )

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 129 of file dbdt04.f.

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

LAPACK                          Version 3.12.0         TESTING/EIG/dbdt04.f(3)