@stdlib/blas-ext-base-sapxsumors

Adds a constant to each single-precision floating-point strided array element and computes the sum using ordinary recursive summation.


Keywords
stdlib, stdmath, statistics, stats, mathematics, math, blas, extended, sum, total, summation, ors, strided, strided array, typed, array, float32, float, single, float32array, javascript, node, node-js, nodejs, strided-array
License
Apache-2.0
Install
npm install @stdlib/blas-ext-base-sapxsumors@0.0.5

Documentation

sapxsumors

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Add a constant to each single-precision floating-point strided array element and compute the sum using ordinary recursive summation.

Installation

npm install @stdlib/blas-ext-base-sapxsumors

Usage

var sapxsumors = require( '@stdlib/blas-ext-base-sapxsumors' );

sapxsumors( N, alpha, x, stride )

Adds a constant to each single-precision floating-point strided array element and computes the sum using ordinary recursive summation.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );
var N = x.length;

var v = sapxsumors( N, 5.0, x, 1 );
// returns 16.0

The function has the following parameters:

  • N: number of indexed elements.
  • x: input Float32Array.
  • stride: index increment for x.

The N and stride parameters determine which elements in x are accessed at runtime. For example, to access every other element in x,

var Float32Array = require( '@stdlib/array-float32' );
var floor = require( '@stdlib/math-base-special-floor' );

var x = new Float32Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var N = floor( x.length / 2 );

var v = sapxsumors( N, 5.0, x, 2 );
// returns 25.0

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float32Array = require( '@stdlib/array-float32' );
var floor = require( '@stdlib/math-base-special-floor' );

var x0 = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var N = floor( x0.length / 2 );

var v = sapxsumors( N, 5.0, x1, 2 );
// returns 25.0

sapxsumors.ndarray( N, alpha, x, stride, offset )

Adds a constant to each single-precision floating-point strided array element and computes the sum using ordinary recursive summation and alternative indexing semantics.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );
var N = x.length;

var v = sapxsumors.ndarray( N, 5.0, x, 1, 0 );
// returns 16.0

The function has the following additional parameters:

  • offset: starting index for x.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access every other value in x starting from the second value

var Float32Array = require( '@stdlib/array-float32' );
var floor = require( '@stdlib/math-base-special-floor' );

var x = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var N = floor( x.length / 2 );

var v = sapxsumors.ndarray( N, 5.0, x, 2, 1 );
// returns 25.0

Notes

  • If N <= 0, both functions return 0.0.
  • Ordinary recursive summation (i.e., a "simple" sum) is performant, but can incur significant numerical error. If performance is paramount and error tolerated, using ordinary recursive summation is acceptable; in all other cases, exercise due caution.

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var Float32Array = require( '@stdlib/array-float32' );
var sapxsumors = require( '@stdlib/blas-ext-base-sapxsumors' );

var x;
var i;

x = new Float32Array( 10 );
for ( i = 0; i < x.length; i++ ) {
    x[ i ] = round( randu()*100.0 );
}
console.log( x );

var v = sapxsumors( x.length, 5.0, x, 1 );
console.log( v );

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

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License

See LICENSE.

Copyright

Copyright © 2016-2021. The Stdlib Authors.