# NAG FL Interfacef06ekf (dasum)

## ▸▿ Contents

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## 1Purpose

f06ekf returns the $1$-norm of the $n$-element real vector $x$.

## 2Specification

Fortran Interface
 Function f06ekf ( n, x, incx)
 Real (Kind=nag_wp) :: f06ekf Integer, Intent (In) :: n, incx Real (Kind=nag_wp), Intent (In) :: x(*)
#include <nag.h>
 double f06ekf_ (const Integer *n, const double x[], const Integer *incx)
The routine may be called by the names f06ekf, nagf_blas_dasum or its BLAS name dasum.

## 3Description

f06ekf, returns via the function name, the $1$-norm
 $|x1|+|x2|+⋯+|xn|$
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.

## 8Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
f06ekf is not threaded in any implementation.