@teamteanpm2024/tempora-dolorem-inventore
v2.0.5
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dsumpw
Calculate the sum of double-precision floating-point strided array elements using pairwise summation.
Installation
npm install @teamteanpm2024/tempora-dolorem-inventore
Alternatively,
- To load the package in a website via a
script
tag without installation and bundlers, use the ES Module available on theesm
branch (see README). - If you are using Deno, visit the
deno
branch (see README for usage intructions). - For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the
umd
branch (see README).
The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
Usage
var dsumpw = require( '@teamteanpm2024/tempora-dolorem-inventore' );
dsumpw( N, x, stride )
Computes the sum of double-precision floating-point strided array elements using pairwise summation.
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, -2.0, 2.0 ] );
var N = x.length;
var v = dsumpw( N, x, 1 );
// returns 1.0
The function has the following parameters:
- N: number of indexed elements.
- x: input
Float64Array
. - stride: index increment for
x
.
The N
and stride parameters determine which elements in the strided array are accessed at runtime. For example, to compute the sum of every other element in x
,
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var v = dsumpw( 4, x, 2 );
// returns 5.0
Note that indexing is relative to the first index. To introduce an offset, use typed array
views.
var Float64Array = require( '@stdlib/array-float64' );
var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var v = dsumpw( 4, x1, 2 );
// returns 5.0
dsumpw.ndarray( N, x, stride, offset )
Computes the sum of double-precision floating-point strided array elements using pairwise summation and alternative indexing semantics.
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, -2.0, 2.0 ] );
var N = x.length;
var v = dsumpw.ndarray( N, x, 1, 0 );
// returns 1.0
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 calculate the sum of every other value in x
starting from the second value
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var v = dsumpw.ndarray( 4, x, 2, 1 );
// returns 5.0
Notes
- If
N <= 0
, both functions return0.0
. - In general, pairwise summation is more numerically stable than ordinary recursive summation (i.e., "simple" summation), with slightly worse performance. While not the most numerically stable summation technique (e.g., compensated summation techniques such as the Kahan–Babuška-Neumaier algorithm are generally more numerically stable), pairwise summation strikes a reasonable balance between numerical stability and performance. If either numerical stability or performance is more desirable for your use case, consider alternative summation techniques.
Examples
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory;
var filledarrayBy = require( '@stdlib/array-filled-by' );
var dsumpw = require( '@teamteanpm2024/tempora-dolorem-inventore' );
var x = filledarrayBy( 10, 'float64', discreteUniform( 0, 100 ) );
console.log( x );
var v = dsumpw( x.length, x, 1 );
console.log( v );
References
- Higham, Nicholas J. 1993. "The Accuracy of Floating Point Summation." SIAM Journal on Scientific Computing 14 (4): 783–99. doi:10.1137/0914050.
See Also
@stdlib/blas-ext/base/dnansumpw
: calculate the sum of double-precision floating-point strided array elements, ignoring NaN values and using pairwise summation.@stdlib/blas-ext/base/dsum
: calculate the sum of double-precision floating-point strided array elements.@stdlib/blas-ext/base/dsumkbn2
: calculate the sum of double-precision floating-point strided array elements using a second-order iterative Kahan–Babuška algorithm.@stdlib/blas-ext/base/dsumors
: calculate the sum of double-precision floating-point strided array elements using ordinary recursive summation.@stdlib/blas-ext/base/gsumpw
: calculate the sum of strided array elements using pairwise summation.@stdlib/blas-ext/base/ssumpw
: calculate the sum of single-precision floating-point strided array elements using pairwise summation.
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.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.