TESTING/EIG/sstt21.f(3)    Library Functions Manual    TESTING/EIG/sstt21.f(3)

NAME
       TESTING/EIG/sstt21.f

SYNOPSIS
   Functions/Subroutines
       subroutine sstt21 (n, kband, ad, ae, sd, se, u, ldu, work, result)
           SSTT21

Function/Subroutine Documentation
   subroutine sstt21 (integer n, integer kband, real, dimension( * ) ad, real,
       dimension( * ) ae, real, dimension( * ) sd, real, dimension( * ) se,
       real, dimension( ldu, * ) u, integer ldu, real, dimension( * ) work,
       real, dimension( 2 ) result)
       SSTT21

       Purpose:


            SSTT21 checks a decomposition of the form

               A = U S U'

            where ' means transpose, A is symmetric tridiagonal, U is orthogonal,
            and S is diagonal (if KBAND=0) or symmetric tridiagonal (if KBAND=1).
            Two tests are performed:

               RESULT(1) = | A - U S U' | / ( |A| n ulp )

               RESULT(2) = | I - UU' | / ( n ulp )

       Parameters
           N

                     N is INTEGER
                     The size of the matrix.  If it is zero, SSTT21 does nothing.
                     It must be at least zero.

           KBAND

                     KBAND is INTEGER
                     The bandwidth of the matrix S.  It may only be zero or one.
                     If zero, then S is diagonal, and SE is not referenced.  If
                     one, then S is symmetric tri-diagonal.

           AD

                     AD is REAL array, dimension (N)
                     The diagonal of the original (unfactored) matrix A.  A is
                     assumed to be symmetric tridiagonal.

           AE

                     AE is REAL array, dimension (N-1)
                     The off-diagonal of the original (unfactored) matrix A.  A
                     is assumed to be symmetric tridiagonal.  AE(1) is the (1,2)
                     and (2,1) element, AE(2) is the (2,3) and (3,2) element, etc.

           SD

                     SD is REAL array, dimension (N)
                     The diagonal of the (symmetric tri-) diagonal matrix S.

           SE

                     SE is REAL array, dimension (N-1)
                     The off-diagonal of the (symmetric tri-) diagonal matrix S.
                     Not referenced if KBSND=0.  If KBAND=1, then AE(1) is the
                     (1,2) and (2,1) element, SE(2) is the (2,3) and (3,2)
                     element, etc.

           U

                     U is REAL array, dimension (LDU, N)
                     The orthogonal matrix in the decomposition.

           LDU

                     LDU is INTEGER
                     The leading dimension of U.  LDU must be at least N.

           WORK

                     WORK is REAL array, dimension (N*(N+1))

           RESULT

                     RESULT is REAL array, dimension (2)
                     The values computed by the two tests described above.  The
                     values are currently limited to 1/ulp, to avoid overflow.
                     RESULT(1) is always modified.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 125 of file sstt21.f.

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

LAPACK                          Version 3.12.0         TESTING/EIG/sstt21.f(3)