Prototype

There is one prototype of stegr available, please see below.

stegr( const char jobz, const char range, const int_t n,
        VectorD& d, VectorE& e, const Scalar >, const Scalar >,
        const int_t il, const int_t iu,
        const Scalar >, int_t& m, VectorW& w, MatrixZ& z,
        VectorISUPPZ& isuppz );

Description

stegr (short for $FRIENDLY_NAME) provides a C++ interface to LAPACK routines SSTEGR, DSTEGR, CSTEGR, and ZSTEGR. stegr computes selected eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix T. Any such unreduced matrix has a well defined set of pairwise different real eigenvalues, the corresponding real eigenvectors are pairwise orthogonal.

The spectrum may be computed either completely or partially by specifying either an interval (VL,VU] or a range of indices IL:IU for the desired eigenvalues.

stegr is a compatability wrapper around the improved ZSTEMR routine. See DSTEMR for further details.

One important change is that the ABSTOL parameter no longer provides any benefit and hence is no longer used.

Note : stegr and ZSTEMR work only on machines which follow IEEE-754 floating-point standard in their handling of infinities and NaNs. Normal execution may create these exceptiona values and hence may abort due to a floating point exception in environments which do not conform to the IEEE-754 standard.

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.

Definition

Defined in header boost/numeric/bindings/lapack/computational/stegr.hpp.

Parameters or Requirements on Types

Complexity

Example

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

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

this will output

[5] 0 1 2 3 4 5

Notes

See Also