@stdlib/math-base-special-rsqrt

Compute the reciprocal square root of a double-precision floating-point number.

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README

Reciprocal Square Root

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Compute the reciprocal of the principal square root of a double-precision floating-point number.

The reciprocal of the principal square root is defined as

Reciprocal square root

Installation

npm install @stdlib/math-base-special-rsqrt

Usage

var rsqrt = require( '@stdlib/math-base-special-rsqrt' );

rsqrt( x )

Computes the reciprocal (inverse) square root of a double-precision floating-point number.

var v = rsqrt( 1.0 );
// returns 1.0

v = rsqrt( 4.0 );
// returns 0.5

v = rsqrt( 100.0 );
// returns 0.1

v = rsqrt( 0.0 );
// returns Infinity

v = rsqrt( NaN );
// returns NaN

v = rsqrt( Infinity );
// returns 0.0

For negative numbers, the reciprocal square root is not defined.

var v = rsqrt( -4.0 );
// returns NaN

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var rsqrt = require( '@stdlib/math-base-special-rsqrt' );

var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = round( randu() * 100.0 );
    console.log( 'rsqrt(%d) = %d', x, rsqrt( x ) );
}

C APIs

Usage

#include "stdlib/math/base/special/rsqrt.h"

stdlib_base_rsqrt( x )

Computes the reciprocal (inverse) square root of a double-precision floating-point number.

double y = stdlib_base_rsqrt( 4.0 );
// returns 0.5

The function accepts the following arguments:

  • x: [in] double input value.
double stdlib_base_rsqrt( const double x );

Examples

#include "stdlib/math/base/special/rsqrt.h"
#include <stdio.h>

int main() {
    double x[] = { 3.14, 9.0, 0.0, 0.0/0.0 };

    double y;
    int i;
    for ( i = 0; i < 4; i++ ) {
        y = stdlib_base_rsqrt( x[ i ] );
        printf( "rsqrt(%lf) = %lf\n", x[ i ], y );
    }
}

See Also

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 © 2016-2022. The Stdlib Authors.