https://github.com/stdlib-js/number-float64-base-ulp-difference
Compute the number of representable double-precision floating-point values that separate two double-precision floating-point numbers along the real number line.
https://github.com/stdlib-js/number-float64-base-ulp-difference
abs diff difference dist distance double error float64 javascript math mathematics node node-js nodejs numbers relative stdlib ulp
Last synced: 11 days ago
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Compute the number of representable double-precision floating-point values that separate two double-precision floating-point numbers along the real number line.
- Host: GitHub
- URL: https://github.com/stdlib-js/number-float64-base-ulp-difference
- Owner: stdlib-js
- License: apache-2.0
- Created: 2025-06-22T07:26:02.000Z (11 months ago)
- Default Branch: main
- Last Pushed: 2026-04-30T03:29:26.000Z (13 days ago)
- Last Synced: 2026-04-30T05:13:32.301Z (13 days ago)
- Topics: abs, diff, difference, dist, distance, double, error, float64, javascript, math, mathematics, node, node-js, nodejs, numbers, relative, stdlib, ulp
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 666 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
- Notice: NOTICE
Awesome Lists containing this project
README
About stdlib...
We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
# ulpdiff
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Compute the number of representable [double-precision][double-precision] floating-point values that separate two [double-precision][double-precision] floating-point numbers along the real number line.
## Installation
```bash
npm install @stdlib/number-float64-base-ulp-difference
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
The [branches.md][branches-url] 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
```javascript
var ulpdiff = require( '@stdlib/number-float64-base-ulp-difference' );
```
#### ulpdiff( x, y )
Computes the number of representable [double-precision][double-precision] floating-point values that separate two [double-precision][double-precision] floating-point numbers along the real number line.
```javascript
var EPS = require( '@stdlib/constants-float64-eps' );
var d = ulpdiff( 1.0, 1.0+EPS );
// returns 1.0
d = ulpdiff( 1.0+EPS, 1.0 );
// returns 1.0
d = ulpdiff( 1.0, 1.0+EPS+EPS );
// returns 2.0
d = ulpdiff( 1.0, NaN );
// returns NaN
d = ulpdiff( NaN, 1.0 );
// returns NaN
d = ulpdiff( NaN, NaN );
// returns NaN
```
## Notes
- Adjacent [double-precision][double-precision] floating-point numbers differ by `1` [ulp][ulp] (unit in the last place).
- Signed zeros differ only in the sign bit but are considered numerically equal, and thus their ULP difference is `0`.
## Examples
```javascript
var EPS = require( '@stdlib/constants-float64-eps' );
var SMALLEST_SUBNORMAL = require( '@stdlib/constants-float64-smallest-subnormal' );
var ulpdiff = require( '@stdlib/number-float64-base-ulp-difference' );
var d = ulpdiff( 1.0, 1.0+EPS );
console.log( d );
// => 1.0
d = ulpdiff( 5.8364e-319, 5.8367e-319 );
console.log( d );
// => 6.0
d = ulpdiff( 0.0, SMALLEST_SUBNORMAL );
console.log( d );
// => 1.0
d = ulpdiff( 0.0, -0.0 );
console.log( d );
// => 0.0
d = ulpdiff( SMALLEST_SUBNORMAL, -SMALLEST_SUBNORMAL );
console.log( d );
// => 2.0
```
* * *
## Notice
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
#### Community
[![Chat][chat-image]][chat-url]
---
## License
See [LICENSE][stdlib-license].
## Copyright
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/number-float64-base-ulp-difference.svg
[npm-url]: https://npmjs.org/package/@stdlib/number-float64-base-ulp-difference
[test-image]: https://github.com/stdlib-js/number-float64-base-ulp-difference/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/number-float64-base-ulp-difference/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/number-float64-base-ulp-difference/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/number-float64-base-ulp-difference?branch=main
[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg
[chat-url]: https://stdlib.zulipchat.com
[stdlib]: https://github.com/stdlib-js/stdlib
[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors
[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/number-float64-base-ulp-difference/tree/deno
[deno-readme]: https://github.com/stdlib-js/number-float64-base-ulp-difference/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/number-float64-base-ulp-difference/tree/umd
[umd-readme]: https://github.com/stdlib-js/number-float64-base-ulp-difference/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/number-float64-base-ulp-difference/tree/esm
[esm-readme]: https://github.com/stdlib-js/number-float64-base-ulp-difference/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/number-float64-base-ulp-difference/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/number-float64-base-ulp-difference/main/LICENSE
[double-precision]: https://en.wikipedia.org/wiki/Double-precision_floating-point_format
[ulp]: https://en.wikipedia.org/wiki/Unit_in_the_last_place