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

NAME
       TESTING/EIG/dsvdch.f

SYNOPSIS
   Functions/Subroutines
       subroutine dsvdch (n, s, e, svd, tol, info)
           DSVDCH

Function/Subroutine Documentation
   subroutine dsvdch (integer n, double precision, dimension( * ) s, double
       precision, dimension( * ) e, double precision, dimension( * ) svd,
       double precision tol, integer info)
       DSVDCH

       Purpose:


            DSVDCH checks to see if SVD(1) ,..., SVD(N) are accurate singular
            values of the bidiagonal matrix B with diagonal entries
            S(1) ,..., S(N) and superdiagonal entries E(1) ,..., E(N-1)).
            It does this by expanding each SVD(I) into an interval
            [SVD(I) * (1-EPS) , SVD(I) * (1+EPS)], merging overlapping intervals
            if any, and using Sturm sequences to count and verify whether each
            resulting interval has the correct number of singular values (using
            DSVDCT). Here EPS=TOL*MAX(N/10,1)*MAZHEP, where MACHEP is the
            machine precision. The routine assumes the singular values are sorted
            with SVD(1) the largest and SVD(N) smallest.  If each interval
            contains the correct number of singular values, INFO = 0 is returned,
            otherwise INFO is the index of the first singular value in the first
            bad interval.

       Parameters
           N

                     N is INTEGER
                     The dimension of the bidiagonal matrix B.

           S

                     S is DOUBLE PRECISION array, dimension (N)
                     The diagonal entries of the bidiagonal matrix B.

           E

                     E is DOUBLE PRECISION array, dimension (N-1)
                     The superdiagonal entries of the bidiagonal matrix B.

           SVD

                     SVD is DOUBLE PRECISION array, dimension (N)
                     The computed singular values to be checked.

           TOL

                     TOL is DOUBLE PRECISION
                     Error tolerance for checking, a multiplier of the
                     machine precision.

           INFO

                     INFO is INTEGER
                     =0 if the singular values are all correct (to within
                        1 +- TOL*MAZHEPS)
                     >0 if the interval containing the INFO-th singular value
                        contains the incorrect number of singular values.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 96 of file dsvdch.f.

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

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