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NAG Toolbox: nag_blast_isum (f16dl)

 Contents

    1  Purpose
    2  Syntax
    7  Accuracy
    9  Example

Purpose

nag_blast_isum (f16dl) sums the elements of an integer vector.

Syntax

[result] = f16dl(n, x, incx)
[result] = nag_blast_isum(n, x, incx)

Description

nag_blast_isum (f16dl) returns the sum
x1 + x2 + + xn  
of the elements of an n-element integer vector x, via the function name.
If n0 on entry, nag_blast_isum (f16dl) immediately returns the value 0.

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

Parameters

Compulsory Input Parameters

1:     n int64int32nag_int scalar
n, the number of elements in x.
2:     x1+n-1×incx int64int32nag_int array
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 int64int32nag_int scalar
The increment in the subscripts of x between successive elements of x.
Constraint: incx0.

Optional Input Parameters

None.

Output Parameters

1:     result int64int32nag_int scalar
The result of the function.

Error Indicators and Warnings

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

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)).

Further Comments

None.

Example

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




fprintf('f16dl example results\n\n');

% sum vector of integers x
n    = int64(5);
x    = [int64(1)  10  11  -2    9];
incx = int64(1);

xsum = f16dl(n, x, incx);

fprintf('sum(');
fprintf('%4d',x);
fprintf(') = %5d\n',xsum);


f16dl example results

sum(   1  10  11  -2   9) =    29

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Chapter Introduction
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