nag_daxpby (f16ecc) (PDF version)
f16 Chapter Contents
f16 Chapter Introduction
NAG C Library Manual

NAG Library Function Document

nag_daxpby (f16ecc)

+ Contents

    1  Purpose
    7  Accuracy
    9  Example

1  Purpose

nag_daxpby (f16ecc) performs the operation
yαx+β y .

2  Specification

#include <nag.h>
#include <nagf16.h>
void  nag_daxpby (Integer n, double alpha, const double x[], Integer incx, double beta, double y[], Integer incy, NagError *fail)

3  Description

nag_daxpby (f16ecc) performs the operation
yα x+β y
where x and y are n-element real vectors, and α and β real scalars. If n is equal to zero, or if α is equal to zero and β is equal to one, this function returns immediately.

4  References

The BLAS Technical Forum Standard (2001) http://www.netlib.org/blas/blast-forum

5  Arguments

1:     nIntegerInput
On entry: n, the number of elements in x and y.
Constraint: n0.
2:     alphadoubleInput
On entry: the scalar α.
3:     x[dim]const doubleInput
Note: the dimension, dim, of the array x must be at least max1,1+n-1incx.
On entry: the vector x.
4:     incxIntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx0.
5:     betadoubleInput
On entry: the scalar β.
6:     y[dim]doubleInput/Output
Note: the dimension, dim, of the array y must be at least max1,1+n-1incy.
On entry: the vector y.
On exit: the updated vector y.
7:     incyIntegerInput
On entry: the increment in the subscripts of y between successive elements of y.
Constraint: incy0.
8:     failNagError *Input/Output
The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

NE_BAD_PARAM
On entry, argument value had an illegal value.
NE_INT
On entry, incx=value.
Constraint: incx0.
On entry, incy=value.
Constraint: incy0.
On entry, n=value.
Constraint: n0.

7  Accuracy

The BLAS standard requires accurate implementations which avoid unnecessary over/underflow (see Section 2.7 of The BLAS Technical Forum Standard (2001)).

8  Further Comments

None.

9  Example

See Section 9 in nag_real_banded_sparse_eigensystem_sol (f12agc) and nag_real_symm_banded_sparse_eigensystem_sol (f12fgc).

nag_daxpby (f16ecc) (PDF version)
f16 Chapter Contents
f16 Chapter Introduction
NAG C Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012