Reciprocal Square Root

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

$$\mathop{\mathrm{rsqrt}}(x)=\frac{1}{\sqrt{x}}$$

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 discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var logEachMap = require( '@stdlib/console/log-each-map' );
var rsqrt = require( '@stdlib/math/base/special/rsqrt' );

var opts = {
    'dtype': 'float64'
};
var x = discreteUniform( 100, 0, 100, opts );

logEachMap( 'rsqrt(%d) = %0.4f', x, rsqrt );

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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( void ) {
    const 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 );
    }
}

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See Also

• @stdlib/math/base/special/sqrt: compute the principal square root of a double-precision floating-point number.