npm package: @stdlib/math-base-special-fast-uint32-log2
Description: Compute an integer binary logarithm (base two).
Author: The Stdlib Authors
Latest version: 0.3.1

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# Binary Logarithm

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Compute an integer [binary logarithm][binary-logarithm].

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

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

</section>

<section class="usage">

## Usage

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

#### log2Uint32( x )

Returns an **approximate** [binary logarithm][binary-logarithm] of an unsigned 32-bit integer `x`.

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

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

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

</section>

<!-- /.usage -->

<section class="notes">

## 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.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
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 );
}
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

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

#### stdlib_base_fast_uint32_log2( x )

Returns an **approximate** [binary logarithm][binary-logarithm] of an unsigned 32-bit integer `x`.

```c
#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.

```c
uint32_t stdlib_base_fast_uint32_log2( const uint32_t x );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#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 );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math-base/special/log2`][@stdlib/math/base/special/log2]</span><span class="delimiter">: </span><span class="description">binary logarithm (base 2).</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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[binary-logarithm]: https://en.wikipedia.org/wiki/Binary_logarithm

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