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## org.netlib.lapack
Class Dstevx

    java.lang.Object
      org.netlib.lapack.Dstevx

    public class Dstevx

extends java.lang.Object

    Following is the description from the original
    Fortran source.  For each array argument, the Java
    version will include an integer offset parameter, so
    the arguments may not match the description exactly.
    Contact seymour@cs.utk.edu with any questions.

     *     ..
     *
     *  Purpose
     *  =======
     *
     *  DSTEVX computes selected eigenvalues and, optionally, eigenvectors
     *  of a real symmetric tridiagonal matrix A.  Eigenvalues and
     *  eigenvectors can be selected by specifying either a range of values
     *  or a range of indices for the desired eigenvalues.
     *
     *  Arguments
     *  =========
     *
     *  JOBZ    (input) CHARACTER*1
     *          = 'N':  Compute eigenvalues only;
     *          = 'V':  Compute eigenvalues and eigenvectors.
     *
     *  RANGE   (input) CHARACTER*1
     *          = 'A': all eigenvalues will be found.
     *          = 'V': all eigenvalues in the half-open interval (VL,VU]
     *                 will be found.
     *          = 'I': the IL-th through IU-th eigenvalues will be found.
     *
     *  N       (input) INTEGER
     *          The order of the matrix.  N >= 0.
     *
     *  D       (input/output) DOUBLE PRECISION array, dimension (N)
     *          On entry, the n diagonal elements of the tridiagonal matrix
     *          A.
     *          On exit, D may be multiplied by a constant factor chosen
     *          to avoid over/underflow in computing the eigenvalues.
     *
     *  E       (input/output) DOUBLE PRECISION array, dimension (max(1,N-1))
     *          On entry, the (n-1) subdiagonal elements of the tridiagonal
     *          matrix A in elements 1 to N-1 of E.
     *          On exit, E may be multiplied by a constant factor chosen
     *          to avoid over/underflow in computing the eigenvalues.
     *
     *  VL      (input) DOUBLE PRECISION
     *  VU      (input) DOUBLE PRECISION
     *          If RANGE='V', the lower and upper bounds of the interval to
     *          be searched for eigenvalues. VL < VU.
     *          Not referenced if RANGE = 'A' or 'I'.
     *
     *  IL      (input) INTEGER
     *  IU      (input) INTEGER
     *          If RANGE='I', the indices (in ascending order) of the
     *          smallest and largest eigenvalues to be returned.
     *          1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0.
     *          Not referenced if RANGE = 'A' or 'V'.
     *
     *  ABSTOL  (input) DOUBLE PRECISION
     *          The absolute error tolerance for the eigenvalues.
     *          An approximate eigenvalue is accepted as converged
     *          when it is determined to lie in an interval [a,b]
     *          of width less than or equal to
     *
     *                  ABSTOL + EPS *   max( |a|,|b| ) ,
     *
     *          where EPS is the machine precision.  If ABSTOL is less
     *          than or equal to zero, then  EPS*|T|  will be used in
     *          its place, where |T| is the 1-norm of the tridiagonal
     *          matrix.
     *
     *          Eigenvalues will be computed most accurately when ABSTOL is
     *          set to twice the underflow threshold 2*DLAMCH('S'), not zero.
     *          If this routine returns with INFO>0, indicating that some
     *          eigenvectors did not converge, try setting ABSTOL to
     *          2*DLAMCH('S').
     *
     *          See "Computing Small Singular Values of Bidiagonal Matrices
     *          with Guaranteed High Relative Accuracy," by Demmel and
     *          Kahan, LAPACK Working Note #3.
     *
     *  M       (output) INTEGER
     *          The total number of eigenvalues found.  0 <= M <= N.
     *          If RANGE = 'A', M = N, and if RANGE = 'I', M = IU-IL+1.
     *
     *  W       (output) DOUBLE PRECISION array, dimension (N)
     *          The first M elements contain the selected eigenvalues in
     *          ascending order.
     *
     *  Z       (output) DOUBLE PRECISION array, dimension (LDZ, max(1,M) )
     *          If JOBZ = 'V', then if INFO = 0, the first M columns of Z
     *          contain the orthonormal eigenvectors of the matrix A
     *          corresponding to the selected eigenvalues, with the i-th
     *          column of Z holding the eigenvector associated with W(i).
     *          If an eigenvector fails to converge (INFO > 0), then that
     *          column of Z contains the latest approximation to the
     *          eigenvector, and the index of the eigenvector is returned
     *          in IFAIL.  If JOBZ = 'N', then Z is not referenced.
     *          Note: the user must ensure that at least max(1,M) columns are
     *          supplied in the array Z; if RANGE = 'V', the exact value of M
     *          is not known in advance and an upper bound must be used.
     *
     *  LDZ     (input) INTEGER
     *          The leading dimension of the array Z.  LDZ >= 1, and if
     *          JOBZ = 'V', LDZ >= max(1,N).
     *
     *  WORK    (workspace) DOUBLE PRECISION array, dimension (5*N)
     *
     *  IWORK   (workspace) INTEGER array, dimension (5*N)
     *
     *  IFAIL   (output) INTEGER array, dimension (N)
     *          If JOBZ = 'V', then if INFO = 0, the first M elements of
     *          IFAIL are zero.  If INFO > 0, then IFAIL contains the
     *          indices of the eigenvectors that failed to converge.
     *          If JOBZ = 'N', then IFAIL is not referenced.
     *
     *  INFO    (output) INTEGER
     *          = 0:  successful exit
     *          < 0:  if INFO = -i, the i-th argument had an illegal value
     *          > 0:  if INFO = i, then i eigenvectors failed to converge.
     *                Their indices are stored in array IFAIL.
     *
     *  =====================================================================
     *
     *     .. Parameters ..

Constructor Summary
`Dstevx()`

Method Summary
`static void` | `dstevx(java.lang.String jobz, java.lang.String range, int n, double[] d, int _d_offset, double[] e, int _e_offset, double vl, double vu, int il, int iu, double abstol, intW m, double[] w, int _w_offset, double[] z, int _z_offset, int ldz, double[] work, int _work_offset, int[] iwork, int _iwork_offset, int[] ifail, int _ifail_offset, intW info)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Dstevx

    public Dstevx()

Method Detail

### dstevx

    public static void dstevx(java.lang.String jobz,
                              java.lang.String range,
                              int n,
                              double[] d,
                              int _d_offset,
                              double[] e,
                              int _e_offset,
                              double vl,
                              double vu,
                              int il,
                              int iu,
                              double abstol,
                              intW m,
                              double[] w,
                              int _w_offset,
                              double[] z,
                              int _z_offset,
                              int ldz,
                              double[] work,
                              int _work_offset,
                              int[] iwork,
                              int _iwork_offset,
                              int[] ifail,
                              int _ifail_offset,
                              intW info)

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