TESTING/EIG/dstt22.f(3)    Library Functions Manual    TESTING/EIG/dstt22.f(3)

NAME
       TESTING/EIG/dstt22.f

SYNOPSIS
   Functions/Subroutines
       subroutine dstt22 (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork,
           result)
           DSTT22

Function/Subroutine Documentation
   subroutine dstt22 (integer n, integer m, integer kband, double precision,
       dimension( * ) ad, double precision, dimension( * ) ae, double
       precision, dimension( * ) sd, double precision, dimension( * ) se,
       double precision, dimension( ldu, * ) u, integer ldu, double precision,
       dimension( ldwork, * ) work, integer ldwork, double precision,
       dimension( 2 ) result)
       DSTT22

       Purpose:


            DSTT22  checks a set of M eigenvalues and eigenvectors,

                A U = U S

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

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

               RESULT(2) = | I - U'U | / ( m ulp )

       Parameters
           N

                     N is INTEGER
                     The size of the matrix.  If it is zero, DSTT22 does nothing.
                     It must be at least zero.

           M

                     M is INTEGER
                     The number of eigenpairs to check.  If it is zero, DSTT22
                     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 DOUBLE PRECISION array, dimension (N)
                     The diagonal of the original (unfactored) matrix A.  A is
                     assumed to be symmetric tridiagonal.

           AE

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

           SD

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

           SE

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

           U

                     U is DOUBLE PRECISION 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 DOUBLE PRECISION array, dimension (LDWORK, M+1)

           LDWORK

                     LDWORK is INTEGER
                     The leading dimension of WORK.  LDWORK must be at least
                     max(1,M).

           RESULT

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

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 137 of file dstt22.f.

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

LAPACK                          Version 3.12.0         TESTING/EIG/dstt22.f(3)