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NAG Toolbox

NAG Toolbox: nag_blast_dsum (f16el)

 Contents

    1  Purpose
    2  Syntax
    7  Accuracy
    9  Example

Purpose

nag_blast_dsum (f16el) sums the elements of a real vector.

Syntax

[result] = f16el(n, x, incx)
[result] = nag_blast_dsum(n, x, incx)

Description

nag_blast_dsum (f16el) returns the sum
x1 + x2 + + xn  
of the elements of an n-element real vector x, via the function name.
If n0 on entry, nag_blast_dsum (f16el) 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 – double array
The vector x. Element xi is stored in xi-1×incx+1, for i=1,2,,n.
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 – double 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 = 1.1,10.2,11.5,-2.7,9.2T .  
function f16el_example


fprintf('f16el example results\n\n');

% sum x
n    = int64(5);
x    = [1.1   10.2    11.5   -2.7    9.2];
incx = int64(1);

[xsum] = f16el(n, x, incx);

fprintf('sum(');
fprintf('%7.1f',x);
fprintf(') = %7.1f\n',xsum);


f16el example results

sum(    1.1   10.2   11.5   -2.7    9.2) =    29.3

PDF version (NAG web site, 64-bit version, 64-bit version)
Chapter Contents
Chapter Introduction
NAG Toolbox

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