NAG Library Routine Document

f06ejf (dnrm2)

1
Purpose

f06ejf (dnrm2) returns the Euclidean norm of the n-element real vector x.

2
Specification

Fortran Interface
Function f06ejf ( n, x, incx)
Real (Kind=nag_wp):: f06ejf
Integer, Intent (In):: n, incx
Real (Kind=nag_wp), Intent (In):: x(*)
C Header Interface
#include <nagmk26.h>
double  f06ejf_ (const Integer *n, const double x[], const Integer *incx)
The routine may be called by its BLAS name dnrm2.

3
Description

f06ejf (dnrm2) returns, via the function name, the Euclidean norm
x2=xTx  
of the n-element real vector x scattered with stride incx.

4
References

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

5
Arguments

1:     n – IntegerInput
On entry: n, the number of elements in x.
2:     x* – Real (Kind=nag_wp) arrayInput
Note: the dimension of the array x must be at least max1, 1+n-1 ×incx .
On entry: the n-element vector x. xi must be stored in x1+i-1×incx, for i=1,2,,n.
Intermediate elements of x are not referenced.
3:     incx – IntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx>0.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06ejf (dnrm2) is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.