TESTING/EIG/sstt22.f(3)

NAME
TESTING/EIG/sstt22.f

SYNOPSIS

  Functions/Subroutines
subroutine sstt22 (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork, result)
SSTT22

Function/Subroutine Documentation

  subroutine sstt22 (integer n, integer m, integer kband, real, dimension( * ) ad, real, dimension( * ) ae, real, dimension( * ) sd, real, dimension( * ) se, real, dimension( ldu, * ) u, integer ldu, real, dimension( ldwork, * ) work, integer ldwork, real, dimension( 2 ) result)

SSTT22

Purpose:

     SSTT22  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, SSTT22 does nothing.
              It must be at least zero.

    M

              M is INTEGER
              The number of eigenpairs to check.  If it is zero, SSTT22
              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)
              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 REAL array, dimension (N)
              The diagonal of the (symmetric tri-) diagonal matrix S.

    SE

              SE is REAL 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 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 (LDWORK, M+1)

    LDWORK

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

    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 137 of file sstt22.f.

Author

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