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feat: add blas/ext/base/gfind-index
PR-URL: #7727 Ref: #2656 Co-authored-by: Athan Reines <[email protected]> Reviewed-by: Athan Reines <[email protected]>
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‎lib/node_modules/@stdlib/blas/ext/base/gfind-index/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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# gfindIndex
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> Return the index of the first element which passes a test implemented by a predicate function.
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<section class="usage">
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## Usage
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```javascript
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var gfindIndex = require( '@stdlib/blas/ext/base/gfind-index' );
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```
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#### gfindIndex( N, x, strideX, clbk\[, thisArg] )
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Returns the index of the first element which passes a test implemented by a predicate function.
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```javascript
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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var x = [ 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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var idx = gfindIndex( x.length, x, 1, isEven );
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// returns 3
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```
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If no element passes a test implemented by a predicate function, the function returns `-1`.
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```javascript
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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var x = [ 1.0, 3.0, 5.0, 7.0, 9.0 ];
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var idx = gfindIndex( x.length, x, 1, isEven );
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// returns -1
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```
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The function has the following parameters:
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- **N**: number of indexed elements.
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- **x**: input array.
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- **strideX**: stride length.
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- **clbk**: callback function.
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- **thisArg**: execution context (_optional_).
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The callback function is provided the following arguments:
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- **value**: current array element.
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- **aidx**: array index.
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- **sidx**: strided index (`offset + aidx*stride`).
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- **array**: the input array.
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To set the callback execution context, provide a `thisArg`.
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```javascript
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function isEven( v ) {
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this.count += 1;
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return v % 2.0 === 0.0;
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}
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var x = [ 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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var ctx = {
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'count': 0
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};
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var idx = gfindIndex( x.length, x, 1, isEven, ctx );
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// returns 3
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var count = ctx.count;
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// returns 4
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```
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The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to test every other element:
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```javascript
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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var x = [ 1.0, 3.0, -5.0, 0.0, 4.0, -1.0, -3.0 ];
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var idx = gfindIndex( 4, x, 2, isEven );
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// returns 2
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```
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Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
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```javascript
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var Float64Array = require( '@stdlib/array/float64' );
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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// Initial array:
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var x0 = new Float64Array( [ 1.0, 3.0, 4.0, -5.0, 7.0, 6.0 ] );
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// Create an offset view:
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var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
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var idx = gfindIndex( 3, x1, 2, isEven );
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// returns 2
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```
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#### gfindIndex.ndarray( N, x, strideX, offsetX, clbk\[, thisArg] )
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Returns the index of the first element which passes a test implemented by a predicate function using alternative indexing semantics.
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```javascript
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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var x = [ 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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var idx = gfindIndex.ndarray( x.length, x, 1, 0, isEven );
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// returns 3
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```
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The function has the following additional parameters:
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- **offsetX**: starting index.
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While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access only the last three elements:
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```javascript
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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var x = [ 1.0, -2.0, -4.0, 5.0, -7.0, 6.0 ];
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var idx = gfindIndex.ndarray( 3, x, 1, x.length-3, isEven );
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// returns 2
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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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## Notes
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- If `N <= 0`, both functions return `-1`.
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- Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).
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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 discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
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var gfindIndex = require( '@stdlib/blas/ext/base/gfind-index' );
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function isEven( v ) {
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return v % 2.0 === 0.0;
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}
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var x = discreteUniform( 10, -100, 100, {
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'dtype': 'generic'
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});
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console.log( x );
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var idx = gfindIndex( x.length, x, 1, isEven );
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console.log( idx );
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```
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</section>
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<!-- /.examples -->
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<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="references">
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</section>
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<!-- /.references -->
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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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[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
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[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor
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</section>
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<!-- /.links -->

‎lib/node_modules/@stdlib/blas/ext/base/gfind-index/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 isInteger = require( '@stdlib/math/base/assert/is-integer' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var pkg = require( './../package.json' ).name;
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var gfindIndex = require( './../lib' );
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// FUNCTIONS //
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/**
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* Callback function.
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*
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* @param {*} v - array element
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* @returns {boolean} result
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*/
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function clbk( v ) {
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return v > 999.0;
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}
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/**
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* Create a benchmark function.
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*
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* @private
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* @param {PositiveInteger} len - array length
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* @returns {Function} benchmark function
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*/
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function createBenchmark( len ) {
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var x = discreteUniform( len, -100.0, 100.0, {
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'dtype': 'generic'
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});
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return benchmark;
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function benchmark( b ) {
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var idx;
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var i;
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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idx = gfindIndex( x.length, x, 1, clbk );
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if ( !isInteger( idx ) ) {
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b.fail( 'should return an integer' );
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}
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}
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b.toc();
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if ( !isInteger( idx ) ) {
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b.fail( 'should return an integer' );
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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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}
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// MAIN //
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function main() {
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var len;
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var min;
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var max;
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var f;
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var i;
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min = 1; // 10^min
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max = 6; // 10^max
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for ( i = min; i <= max; i++ ) {
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len = pow( 10, i );
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f = createBenchmark( len );
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bench( pkg+':len='+len, f );
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}
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}
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main();

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