Binary Logarithm

Compute an integer binary logarithm.

Installation

npm install @stdlib/math-base-special-fast-uint32-log2

Usage

var log2Uint32 = require( '@stdlib/math-base-special-fast-uint32-log2' );

log2Uint32( x )

Returns an approximate binary logarithm of an unsigned 32-bit integer x.

var v = log2Uint32( 4 >>> 0 );
// returns 2

v = log2Uint32( 8 >>> 0 );
// returns 3

v = log2Uint32( 9 >>> 0 );
// returns 3

Notes

• This implementation provides a performance boost when an application requires only approximate computations for integer arguments.
• For applications requiring high-precision, this implementation is never suitable.

Examples

var log2Uint32 = require( '@stdlib/math-base-special-fast-uint32-log2' );

var v;
var i;

for ( i = 1; i < 101; i++ ) {
    v = log2Uint32( i >>> 0 );
    console.log( 'log2(%d) ≈ %d', i, v );
}

C APIs

Usage

#include "stdlib/math/base/special/fast/uint32_log2.h"

stdlib_base_fast_uint32_log2( x )

Returns an approximate binary logarithm of an unsigned 32-bit integer x.

#include <stdint.h>

uint32_t out = stdlib_base_fast_uint32_log2( 4 );
// returns 2

out = stdlib_base_fast_uint32_log2( 9 );
// returns 3

The function accepts the following arguments:

• x: [in] uint32_t input value.

uint32_t stdlib_base_fast_uint32_log2( const uint32_t x );

Examples

#include "stdlib/math/base/special/fast/uint32_log2.h"
#include <stdio.h>
#include <stdint.h>

int main( void ) {
    const uint32_t x[] = { 5, 7, 10, 22, 98 };

    uint32_t y;
    int i;
    for ( i = 0; i < 5; i++ ) {
        y = stdlib_base_fast_uint32_log2( x[ i ] );
        printf( "uint32_log2(%u) = %u\n", x[ i ], y );
    }
}

See Also

• @stdlib/math-base/special/log2: binary logarithm (base 2).

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.