TESTING/EIG/zstt22.f(3)

NAME
TESTING/EIG/zstt22.f

SYNOPSIS

  Functions/Subroutines
subroutine zstt22 (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork, rwork, result)
ZSTT22

Function/Subroutine Documentation

  subroutine zstt22 (integer n, integer m, integer kband, double precision, dimension( * ) ad, double precision, dimension( * ) ae, double precision, dimension( * ) sd, double precision, dimension( * ) se, complex*16, dimension( ldu, * ) u, integer ldu, complex*16, dimension( ldwork, * ) work, integer ldwork, double precision, dimension( * ) rwork, double precision, dimension( 2 ) result)

ZSTT22

Purpose:

     ZSTT22  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, ZSTT22 does nothing.
              It must be at least zero.

    M

              M is INTEGER
              The number of eigenpairs to check.  If it is zero, ZSTT22
              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 DOUBLE PRECISION array, dimension (N)
              The diagonal of the original (unfactored) matrix A.  A is
              assumed to be Hermitian tridiagonal.

    AE

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

    SE

              SE is DOUBLE PRECISION 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 DOUBLE PRECISION 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*16 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 DOUBLE PRECISION array, dimension (N)

    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 143 of file zstt22.f.

Author

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