NAG FL Interfacef06ejf (dnrm2)

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1Purpose

f06ejf returns the Euclidean norm of the $n$-element real vector $x$.

2Specification

Fortran Interface
 Function f06ejf ( n, x, incx)
 Real (Kind=nag_wp) :: f06ejf Integer, Intent (In) :: n, incx Real (Kind=nag_wp), Intent (In) :: x(*)
#include <nag.h>
 double f06ejf_ (const Integer *n, const double x[], const Integer *incx)
The routine may be called by the names f06ejf, nagf_blas_dnrm2 or its BLAS name dnrm2.

3Description

f06ejf returns, via the function name, the Euclidean norm
 $‖x‖2=xTx$
of the $n$-element real vector $x$ scattered with stride incx.

4References

Lawson C L, Hanson R J, Kincaid D R and Krogh F T (1979) Basic linear algebra supbrograms for Fortran usage ACM Trans. Math. Software 5 308–325

5Arguments

1: $\mathbf{n}$Integer Input
On entry: $n$, the number of elements in $x$.
2: $\mathbf{x}\left(*\right)$Real (Kind=nag_wp) array Input
Note: the dimension of the array x must be at least $\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,1+\left({\mathbf{n}}-1\right)×{\mathbf{incx}}\right)$.
On entry: the $n$-element vector $x$. ${x}_{\mathit{i}}$ must be stored in ${\mathbf{x}}\left(1+\left(\mathit{i}-1\right)×{\mathbf{incx}}\right)$, for $\mathit{i}=1,2,\dots ,{\mathbf{n}}$.
Intermediate elements of x are not referenced.
3: $\mathbf{incx}$Integer Input
On entry: the increment in the subscripts of x between successive elements of $x$.
Constraint: ${\mathbf{incx}}>0$.

None.

Not applicable.