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

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