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feat: add blas/ext/base/gmskrev
PR-URL: #10925 Co-authored-by: Athan Reines <kgryte@gmail.com> Reviewed-by: Athan Reines <kgryte@gmail.com> Signed-off-by: Athan Reines <kgryte@gmail.com> Closes: stdlib-js/metr-issue-tracker#195
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‎lib/node_modules/@stdlib/blas/ext/base/gmskrev/README.md‎

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<!--
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@license Apache-2.0
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Copyright (c) 2026 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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# gmskrev
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> Reverse a strided array in-place according to a mask.
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<section class="usage">
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## Usage
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```javascript
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var gmskrev = require( '@stdlib/blas/ext/base/gmskrev' );
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```
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#### gmskrev( N, x, strideX, mask, strideMask )
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Reverses a strided array in-place according to a mask.
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```javascript
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var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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var mask = [ 0, 0, 0, 1, 0, 0, 0, 0 ];
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gmskrev( x.length, x, 1, mask, 1 );
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// x => [ -3.0, -1.0, 0.0, -5.0, 4.0, 3.0, 1.0, -2.0 ]
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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 for `x`.
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- **mask**: mask array. If a `mask` array element is `0`, the corresponding element in `x` is considered valid and **included** in the reversal. If a `mask` array element is `1`, the corresponding element in `x` is considered invalid/missing and **excluded** from the reversal.
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- **strideMask**: stride length for `mask`.
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The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to reverse every other element:
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```javascript
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var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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var mask = [ 0, 0, 0, 0 ];
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gmskrev( 4, x, 2, mask, 1 );
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// x => [ -1.0, 1.0, 4.0, -5.0, 3.0, 0.0, -2.0, -3.0 ]
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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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var Uint8Array = require( '@stdlib/array/uint8' );
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// Initial arrays...
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var x0 = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
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var m0 = new Uint8Array( [ 0, 0, 0, 0, 0, 0 ] );
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// Create offset views...
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var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
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var m1 = new Uint8Array( m0.buffer, m0.BYTES_PER_ELEMENT*1 );
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// Reverse every other element...
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gmskrev( 3, x1, 2, m1, 1 );
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// x0 => <Float64Array>[ 1.0, -6.0, 3.0, -4.0, 5.0, -2.0 ]
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```
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#### gmskrev.ndarray( N, x, strideX, offsetX, mask, strideMask, offsetMask )
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Reverses a strided array in-place according to a mask and using alternative indexing semantics.
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```javascript
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var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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var mask = [ 0, 0, 0, 1, 0, 0, 0, 0 ];
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gmskrev.ndarray( x.length, x, 1, 0, mask, 1, 0 );
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// x => [ -3.0, -1.0, 0.0, -5.0, 4.0, 3.0, 1.0, -2.0 ]
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```
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The function has the following additional parameters:
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- **offsetX**: starting index for `x`.
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- **offsetMask**: starting index for `mask`.
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While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to access only the last three elements:
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```javascript
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var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];
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var mask = [ 0, 0, 0, 0, 0, 0 ];
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gmskrev.ndarray( 3, x, 1, x.length-3, mask, 1, 3 );
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// x => [ 1.0, -2.0, 3.0, -6.0, 5.0, -4.0 ]
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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 `x` unchanged.
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- Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/complex64`][@stdlib/array/complex64]).
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- Where possible, one should "reverse" a strided array by negating its stride, which is an `O(1)` operation, in contrast to performing an in-place reversal, which is `O(N)`. However, in certain circumstances, this is not tenable, particularly when interfacing with libraries which assume and/or expect a specific memory layout (e.g., strided array elements arranged in memory in ascending order). In general, when working with strided arrays, only perform an in-place reversal when strictly necessary.
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- Depending on the environment, the typed versions ([`dmskrev`][@stdlib/blas/ext/base/dmskrev], [`smskrev`][@stdlib/blas/ext/base/smskrev], etc.) are likely to be significantly more performant.
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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 Uint8Array = require( '@stdlib/array/uint8' );
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var gmskrev = require( '@stdlib/blas/ext/base/gmskrev' );
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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 mask = new Uint8Array( [ 0, 0, 0, 1, 0, 0, 1, 0, 0, 0 ] );
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console.log( mask );
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gmskrev( x.length, x, 1, mask, 1 );
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console.log( x );
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```
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</section>
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<!-- /.examples -->
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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/complex64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex64
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[@stdlib/blas/ext/base/dmskrev]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/ext/base/dmskrev
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[@stdlib/blas/ext/base/smskrev]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/ext/base/smskrev
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<!-- <related-links> -->
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<!-- </related-links> -->
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</section>
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<!-- /.links -->

‎lib/node_modules/@stdlib/blas/ext/base/gmskrev/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) 2026 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 uniform = require( '@stdlib/random/array/uniform' );
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var isnan = require( '@stdlib/math/base/assert/is-nan' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var zeros = require( '@stdlib/array/zeros' );
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var format = require( '@stdlib/string/format' );
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var pkg = require( './../package.json' ).name;
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var gmskrev = require( './../lib/main.js' );
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// FUNCTIONS //
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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 mask = zeros( len, 'uint8' );
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var x = uniform( 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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/**
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* Benchmark function.
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*
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* @private
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* @param {Benchmark} b - benchmark instance
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*/
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function benchmark( b ) {
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var y;
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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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y = gmskrev( x.length, x, 1, mask, 1 );
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if ( isnan( y[ i%x.length ] ) ) {
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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 ( isnan( y[ i%x.length ] ) ) {
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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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}
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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( format( '%s:len=%d', pkg, len ), f );
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}
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}
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main();

‎lib/node_modules/@stdlib/blas/ext/base/gmskrev/benchmark/benchmark.ndarray.js‎

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2026 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 uniform = require( '@stdlib/random/array/uniform' );
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var isnan = require( '@stdlib/math/base/assert/is-nan' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var zeros = require( '@stdlib/array/zeros' );
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var format = require( '@stdlib/string/format' );
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var pkg = require( './../package.json' ).name;
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var gmskrev = require( './../lib/ndarray.js' );
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// FUNCTIONS //
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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 mask = zeros( len, 'uint8' );
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var x = uniform( 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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/**
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* Benchmark function.
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*
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* @private
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* @param {Benchmark} b - benchmark instance
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*/
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function benchmark( b ) {
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var y;
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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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y = gmskrev( x.length, x, 1, 0, mask, 1, 0 );
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if ( isnan( y[ i%x.length ] ) ) {
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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 ( isnan( y[ i%x.length ] ) ) {
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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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}
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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( format( '%s:ndarray:len=%d', pkg, len ), f );
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}
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}
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main();

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