ulpdiff

Compute the number of representable double-precision floating-point values that separate two double-precision floating-point numbers along the real number line.

Installation

npm install @stdlib/number-float64-base-ulp-difference

Usage

var ulpdiff = require( '@stdlib/number-float64-base-ulp-difference' );

ulpdiff( x, y )

Computes the number of representable double-precision floating-point values that separate two double-precision floating-point numbers along the real number line.

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 floating-point numbers differ by 1 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

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, 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 © 2016-2026. The Stdlib Authors.