NAG Library Routine Document

f06klf  (idrank)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06klf determines the index of the first negligible element of a real vector.

2
Specification

Fortran Interface
Function f06klf ( n, x, incx, tol)
Integer:: f06klf
Integer, Intent (In):: n, incx
Real (Kind=nag_wp), Intent (In):: x(*), tol
C Header Interface
#include nagmk26.h
Integer  f06klf_ ( const Integer *n, const double x[], const Integer *incx, const double *tol)

3
Description

f06klf finds the first element of the n-element real vector x for which
xk+1tolmaxx1,,xk  
and returns the index k via the function name. If no such k exists, then the value n is returned. If a negative value of tol is supplied, the value of machine precision is used in place of tol.

4
References

None.

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.
4:     tol – Real (Kind=nag_wp)Input
On entry: the value tol.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06klf is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017