##### spr

###### Prototype

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

    spr( const Scalar >, const VectorX& x, MatrixAP& ap );

###### Description

`spr` (short for symmetric, packed, rank-1 update) provides a C++ interface to BLAS routines SSPR and DSPR. `spr` performs the symmetric rank 1 operation

A := alpha*x*x' + A,

where alpha is a real scalar, x is an n element vector and A is an n by n symmetric matrix, supplied in packed form.

The selection of the BLAS routine is done during compile-time, and is determined by the type of values contained in type `VectorX`. The type of values is obtained through the `value_type` meta-function `typename value_type<VectorX>::type`. Table X below illustrates to which specific routine this dispatching will take place.

Table 1.62. Dispatching of spr.

Value type of VectorX | BLAS routine | CBLAS routine | CUBLAS routine
--- | --- | --- | ---
`float` | SSPR | cblas_sspr | cublasSspr
`double` | DSPR | cblas_dspr | Unavailable

The original routines SSPR and DSPR have six arguments, whereas `spr` requires three arguments.

Table 1.63. Deduction of arguments of spr.

###### Definition

Defined in header `boost/numeric/bindings/blas/level2/spr.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/blas/level2/spr.hpp>
    using namespace boost::numeric::bindings;

    blas::spr( x, y, z );

this will output

    [5] 0 1 2 3 4 5

###### Notes

###### See Also

- Originating Fortran source files sspr.f and dspr.f at Netlib.