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feat: add math/base/special/fibonacci-indexf
PR-URL: #6320 Ref: #649 Co-authored-by: Athan Reines <[email protected]> Reviewed-by: Athan Reines <[email protected]> Co-authored-by: stdlib-bot <[email protected]>
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Diff for: ‎lib/node_modules/@stdlib/math/base/special/fibonacci-indexf/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2025 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Fibonacci Number Index
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> Compute the [Fibonacci number][fibonacci-number] index of a single-precision floating-point number.
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<section class="intro">
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The [Fibonacci number][fibonacci-number] index is given by
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<!-- <equation class="equation" label="eq:fibonacci_number_indexf" align="center" raw="n = \left \lfloor{\log_\varphi \biggl(F \cdot \sqrt{5} + \tfrac{1}{2}\biggr)}\right \rfloor" alt="Formula to compute the Fibonacci number index."> -->
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```math
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n = \left \lfloor{\log_\varphi \biggl(F \cdot \sqrt{5} + \tfrac{1}{2}\biggr)}\right \rfloor
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```
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<!-- </equation> -->
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where `φ` is the [golden ratio][golden-ratio] and `F > 1`.
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</section>
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<!-- /.intro -->
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<section class="usage">
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## Usage
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```javascript
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var fibonacciIndexf = require( '@stdlib/math/base/special/fibonacci-indexf' );
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```
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#### fibonacciIndexf( F )
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Computes the [Fibonacci number][fibonacci-number] index of a single-precision floating-point number.
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```javascript
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var n = fibonacciIndexf( 2 );
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// returns 3
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n = fibonacciIndexf( 3 );
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// returns 4
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n = fibonacciIndexf( 5 );
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// returns 5
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```
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If provided either a non-integer or `F_n <= 1`, the function returns `NaN`.
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```javascript
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var n = fibonacciIndexf( -1 );
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// returns NaN
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n = fibonacciIndexf( 3.14 );
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// returns NaN
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```
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If provided `NaN`, the function returns `NaN`.
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```javascript
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var n = fibonacciIndexf( NaN );
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// returns NaN
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var fibonacciIndexf = require( '@stdlib/math/base/special/fibonacci-indexf' );
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var F1;
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var F2;
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var FN;
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var n;
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var i;
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F1 = 1;
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F2 = 1;
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for ( i = 3; i < 37; i++ ) {
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FN = F1 + F2;
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F1 = F2;
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F2 = FN;
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n = fibonacciIndexf( FN );
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console.log( 'n(%d) = %d', FN, n );
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}
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```
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</section>
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<!-- /.examples -->
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<!-- C interface documentation. -->
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* * *
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<section class="c">
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## C APIs
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- C usage documentation. -->
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<section class="usage">
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### Usage
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```c
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#include "stdlib/math/base/special/fibonacci_indexf.h"
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```
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#### stdlib_base_fibonacci_indexf( F )
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Computes the [Fibonacci number][fibonacci-number] index of a single-precision floating-point number.
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```c
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float out = stdlib_base_fibonacci_indexf( 2.0f );
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// returns 3.0f
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out = stdlib_base_fibonacci_indexf( 3.0f );
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// returns 4.0f
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```
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The function accepts the following arguments:
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- **F**: `[in] float` input value.
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```c
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float stdlib_base_fibonacci_indexf( const float F );
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```
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</section>
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<!-- /.usage -->
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<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- C API usage examples. -->
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<section class="examples">
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### Examples
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```c
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#include "stdlib/math/base/special/fibonacci_indexf.h"
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#include <stdio.h>
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int main( void ) {
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const float x[] = { 2.0f, 3.0f, 5.0f, 8.0f };
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float y;
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int i;
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for ( i = 0; i < 4; i++ ) {
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y = stdlib_base_fibonacci_indexf( x[ i ] );
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printf( "fibonacci_indexf(%f) = %f\n", x[ i ], y );
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}
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}
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.c -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[fibonacci-number]: https://en.wikipedia.org/wiki/Fibonacci_number
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[golden-ratio]: https://en.wikipedia.org/wiki/Golden_ratio
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<!-- <related-links> -->
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<!-- </related-links> -->
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</section>
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<!-- /.links -->

Diff for: ‎lib/node_modules/@stdlib/math/base/special/fibonacci-indexf/benchmark/benchmark.js

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
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var zeros = require( '@stdlib/array/base/zeros' );
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var isnanf = require( '@stdlib/math/base/assert/is-nanf' );
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var fibonacci = require( '@stdlib/math/base/special/fibonacci' );
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var pkg = require( './../package.json' ).name;
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var fibonacciIndexf = require( './../lib' );
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// MAIN //
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bench( pkg, function benchmark( b ) {
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var FN;
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var x;
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var y;
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var i;
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FN = zeros( 37 );
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for ( i = 3; i < 37; i++ ) {
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FN[ i ] = fibonacci( i );
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}
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x = discreteUniform( 100, 3, 36 );
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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y = fibonacciIndexf( FN[ x[ i%x.length ] ] );
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if ( isnanf( y ) ) {
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b.fail( 'should not return NaN' );
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}
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}
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b.toc();
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if ( isnanf( y ) ) {
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b.fail( 'should not return NaN' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});

Diff for: ‎lib/node_modules/@stdlib/math/base/special/fibonacci-indexf/benchmark/benchmark.native.js

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var resolve = require( 'path' ).resolve;
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var bench = require( '@stdlib/bench' );
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var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
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var zeros = require( '@stdlib/array/base/zeros' );
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var isnanf = require( '@stdlib/math/base/assert/is-nanf' );
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var fibonacci = require( '@stdlib/math/base/special/fibonacci' );
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var tryRequire = require( '@stdlib/utils/try-require' );
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var pkg = require( './../package.json' ).name;
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// VARIABLES //
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var fibonacciIndexf = tryRequire( resolve( __dirname, './../lib/native.js' ) );
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var opts = {
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'skip': ( fibonacciIndexf instanceof Error )
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};
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// MAIN //
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bench( pkg+'::native', opts, function benchmark( b ) {
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var FN;
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var x;
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var y;
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var i;
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FN = zeros( 37 );
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for ( i = 3; i < 37; i++ ) {
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FN[ i ] = fibonacci( i );
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}
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x = discreteUniform( 100, 3, 36 );
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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y = fibonacciIndexf( FN[ x[ i%x.length ] ] );
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if ( isnanf( y ) ) {
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b.fail( 'should not return NaN' );
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}
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}
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b.toc();
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if ( isnanf( y ) ) {
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b.fail( 'should not return NaN' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});

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