##### stein

###### Prototype

There is one prototype of `stein` available, please see below.

    stein( const int_t n, const VectorD& d, const VectorE& e,
            const int_t m, const VectorW& w,
            const VectorIBLOCK& iblock, const VectorISPLIT& isplit, MatrixZ& z,
            VectorIFAIL& ifail );

###### Description

`stein` (short for $FRIENDLY_NAME) provides a C++ interface to LAPACK routines SSTEIN, DSTEIN, CSTEIN, and ZSTEIN. `stein` computes the eigenvectors of a real symmetric tridiagonal matrix T corresponding to specified eigenvalues, using inverse iteration.

The maximum number of iterations allowed for each eigenvector is specified by an internal parameter MAXITS (currently set to 5).

Although the eigenvectors are real, they are stored in a complex array, which may be passed to ZUNMTR or ZUPMTR for back transformation to the eigenvectors of a complex Hermitian matrix which was reduced to tridiagonal form.

The selection of the LAPACK routine is done during compile-time, and is determined by the type of values contained in type `VectorD`. The type of values is obtained through the `value_type` meta-function `typename value_type<VectorD>::type`. The dispatching table below illustrates to which specific routine the code path will be generated.

Table 1.321. Dispatching of stein

Value type of VectorD | LAPACK routine
--- | ---
`float` | SSTEIN
`double` | DSTEIN
`complex<float>` | CSTEIN
`complex<double>` | ZSTEIN

###### Definition

Defined in header `boost/numeric/bindings/lapack/computational/stein.hpp`.

###### Parameters or Requirements on Types

Parameters

MatrixA

  The definition of term 1

MatrixB

  The definition of term 2

MatrixC

  The definition of term 3.

  Definitions may contain paragraphs.

###### Complexity

###### Example

    #include <boost/numeric/bindings/lapack/computational/stein.hpp>
    using namespace boost::numeric::bindings;

    lapack::stein( x, y, z );

this will output

    [5] 0 1 2 3 4 5

###### Notes

###### See Also

- Originating Fortran source files sstein.f, dstein.f, cstein.f, and zstein.f at Netlib.