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feat: add blas/base/zdscal
PR-URL: stdlib-js#4738 Ref: stdlib-js#2464 Ref: stdlib-js#2039 Co-authored-by: Athan Reines <[email protected]> Reviewed-by: Athan Reines <[email protected]>
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‎lib/node_modules/@stdlib/blas/base/zdscal/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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# zdscal
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> Scale a double-precision complex floating-point vector by a double-precision floating-point constant.
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<section class="usage">
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## Usage
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```javascript
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var zdscal = require( '@stdlib/blas/base/zdscal' );
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```
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#### zdscal( N, da, zx, strideZX )
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Scales a double-precision complex floating-point vector by a double-precision floating-point constant.
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```javascript
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var Complex128Array = require( '@stdlib/array/complex128' );
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var real = require( '@stdlib/complex/float64/real' );
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var imag = require( '@stdlib/complex/float64/imag' );
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var zx = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );
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zdscal( 3, 2.0, zx, 1 );
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var z = zx.get( 0 );
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// returns <Complex128>
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var re = real( z );
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// returns 2.0
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var im = imag( z );
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// returns 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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- **da**: scalar constant.
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- **zx**: input [`Complex128Array`][@stdlib/array/complex128].
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- **strideZX**: stride length for `zx`.
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The `N` and stride parameters determine which elements in `zx` are scaled by `da`. For example, to scale every other element in `zx` by `da`,
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```javascript
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var Complex128Array = require( '@stdlib/array/complex128' );
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var real = require( '@stdlib/complex/float64/real' );
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var imag = require( '@stdlib/complex/float64/imag' );
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var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
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zdscal( 2, 2.0, zx, 2 );
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var z = zx.get( 2 );
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// returns <Complex128>
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var re = real( z );
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// returns 10.0
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var im = imag( z );
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// returns 12.0
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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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<!-- eslint-disable stdlib/capitalized-comments -->
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```javascript
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var Complex128Array = require( '@stdlib/array/complex128' );
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var real = require( '@stdlib/complex/float64/real' );
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var imag = require( '@stdlib/complex/float64/imag' );
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// Initial array:
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var zx0 = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
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// Create an offset view:
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var zx1 = new Complex128Array( zx0.buffer, zx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
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// Scale every element in `zx1`:
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zdscal( 3, 2.0, zx1, 1 );
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var z = zx0.get( 0 );
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// returns <Complex128>
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var re = real( z );
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// returns 1.0
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var im = imag( z );
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// returns 2.0
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z = zx0.get( 1 );
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// returns <Complex128>
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re = real( z );
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// returns 6.0
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im = imag( z );
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// returns 8.0
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```
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#### zdscal.ndarray( N, da, zx, strideZX, offsetZX )
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Scales a double-precision complex floating-point vector by a double-precision floating-point constant using alternative indexing semantics.
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```javascript
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var Complex128Array = require( '@stdlib/array/complex128' );
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var real = require( '@stdlib/complex/float64/real' );
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var imag = require( '@stdlib/complex/float64/imag' );
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var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
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zdscal.ndarray( 3, 2.0, zx, 1, 0 );
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var z = zx.get( 0 );
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// returns <Complex128>
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var re = real( z );
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// returns 2.0
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var im = imag( z );
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// returns 4.0
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```
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The function has the following additional parameters:
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- **offsetZX**: starting index for `zx`.
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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 scale every other element in the input strided array starting from the second element,
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```javascript
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var Complex128Array = require( '@stdlib/array/complex128' );
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var real = require( '@stdlib/complex/float64/real' );
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var imag = require( '@stdlib/complex/float64/imag' );
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var zx = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
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zdscal.ndarray( 2, 2.0, zx, 2, 1 );
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var z = zx.get( 3 );
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// returns <Complex128>
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var re = real( z );
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// returns 14.0
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var im = imag( z );
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// returns 16.0
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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 `zx` unchanged.
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- `zdscal()` corresponds to the [BLAS][blas] level 1 function [`zdscal`][zdscal].
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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/base/discrete-uniform' );
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var filledarrayBy = require( '@stdlib/array/filled-by' );
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var Complex128 = require( '@stdlib/complex/float64/ctor' );
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var zdscal = require( '@stdlib/blas/base/zdscal' );
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function rand() {
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return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
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}
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var zx = filledarrayBy( 10, 'complex128', rand );
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console.log( zx.toString() );
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zdscal( zx.length, 2.0, zx, 1 );
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console.log( zx.toString() );
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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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[blas]: http://www.netlib.org/blas
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[zdscal]: https://www.netlib.org/lapack/explore-html/d2/de8/group__scal_ga40d50a435a5fcf16cf41fa80d746819f.html#ga40d50a435a5fcf16cf41fa80d746819f
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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/complex128]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex128
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</section>
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<!-- /.links -->

‎lib/node_modules/@stdlib/blas/base/zdscal/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 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 Complex128Array = require( '@stdlib/array/complex128' );
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var pkg = require( './../package.json' ).name;
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var zdscal = require( './../lib/zdscal.js' );
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// VARIABLES //
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var options = {
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'dtype': 'float64'
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};
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// FUNCTIONS //
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/**
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* Creates 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 zxbuf;
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var zx;
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zxbuf = uniform( len*2, -100.0, 100.0, options );
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zx = new Complex128Array( zxbuf.buffer );
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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 i;
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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zdscal( zx.length, 2.0, zx, 1 );
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if ( isnan( zxbuf[ i%(len*2) ] ) ) {
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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( zxbuf[ i%(len*2) ] ) ) {
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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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/**
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* Main execution sequence.
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*
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* @private
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*/
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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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