TESTING/EIG/cstt22.f(3)    Library Functions Manual    TESTING/EIG/cstt22.f(3)

NAME
       TESTING/EIG/cstt22.f

SYNOPSIS
   Functions/Subroutines
       subroutine cstt22 (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork,
           rwork, result)
           CSTT22

Function/Subroutine Documentation
   subroutine cstt22 (integer n, integer m, integer kband, real, dimension( *
       ) ad, real, dimension( * ) ae, real, dimension( * ) sd, real,
       dimension( * ) se, complex, dimension( ldu, * ) u, integer ldu,
       complex, dimension( ldwork, * ) work, integer ldwork, real, dimension(
       * ) rwork, real, dimension( 2 ) result)
       CSTT22

       Purpose:


            CSTT22  checks a set of M eigenvalues and eigenvectors,

                A U = U S

            where A is Hermitian tridiagonal, the columns of U are unitary,
            and S is diagonal (if KBAND=0) or Hermitian 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, CSTT22 does nothing.
                     It must be at least zero.

           M

                     M is INTEGER
                     The number of eigenpairs to check.  If it is zero, CSTT22
                     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 Hermitian tri-diagonal.

           AD

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

           AE

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

           SD

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

           SE

                     SE is REAL array, dimension (N)
                     The off-diagonal of the (Hermitian 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 REAL array, dimension (LDU, N)
                     The unitary matrix in the decomposition.

           LDU

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

           WORK

                     WORK is COMPLEX array, dimension (LDWORK, M+1)

           LDWORK

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

           RWORK

                     RWORK is REAL array, dimension (N)

           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.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 143 of file cstt22.f.

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

LAPACK                          Version 3.12.0         TESTING/EIG/cstt22.f(3)