NAG Library Routine Document

f16dlf  (isum)

 Contents

    1  Purpose
    7  Accuracy

1
Purpose

f16dlf sums the elements of an integer vector.

2
Specification

Fortran Interface
Function f16dlf ( n, x, incx)
Integer:: f16dlf
Integer, Intent (In):: n, x(1+(n-1)*ABS(incx)), incx
C Header Interface
#include nagmk26.h
Integer  f16dlf_ ( const Integer *n, const Integer x[], const Integer *incx)

3
Description

f16dlf returns the sum
x1 + x2 + + xn  
of the elements of an n-element integer vector x, via the function name.
If n0 on entry, f16dlf immediately returns the value 0.

4
References

Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001) Basic Linear Algebra Subprograms Technical (BLAST) Forum Standard University of Tennessee, Knoxville, Tennessee http://www.netlib.org/blas/blast-forum/blas-report.pdf

5
Arguments

1:     n – IntegerInput
On entry: n, the number of elements in x.
2:     x1+n-1×incx – Integer arrayInput
On entry: the n-element vector x.
If incx>0, xi must be stored in xi-1×incx+1, for i=1,2,,n.
If incx<0, xi must be stored in xn-i×incx+1, for i=1,2,,n.
Intermediate elements of x are not referenced. If n=0, x is not referenced.
3:     incx – IntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx0.

6
Error Indicators and Warnings

If incx=0, an error message is printed and program execution is terminated.

7
Accuracy

The BLAS standard requires accurate implementations which avoid unnecessary over/underflow (see Section 2.7 of Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001)).

8
Parallelism and Performance

f16dlf is not threaded in any implementation.

9
Further Comments

None.

10
Example

This example computes the sum of the elements of
x = 1,10,11,-2,9T .  

10.1
Program Text

Program Text (f16dlfe.f90)

10.2
Program Data

Program Data (f16dlfe.d)

10.3
Program Results

Program Results (f16dlfe.r)

© The Numerical Algorithms Group Ltd, Oxford, UK. 2017