NAG Library Routine Document

f06jlf  (idamax)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06jlf (idamax) computes the index of the absolutely largest component of a real vector.

2
Specification

Fortran Interface
Function f06jlf ( n, x, incx)
Integer:: f06jlf
Integer, Intent (In):: n, incx
Real (Kind=nag_wp), Intent (In):: x(*)
C Header Interface
#include nagmk26.h
Integer  f06jlf_ ( const Integer *n, const double x[], const Integer *incx)
The routine may be called by its BLAS name idamax.

3
Description

f06jlf (idamax) returns, via the function name, the smallest index i such that
xi=maxjxj  
where x is an n-element real vector 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

f06jlf (idamax) is not threaded in any implementation.

9
Further Comments

None.

10
Example

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