Binary Logarithm

Compute an integer binary logarithm.

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 );
    }
}