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PR-URL: stdlib-js#2104 Ref: stdlib-js#2039 Co-authored-by: Athan Reines <[email protected]> Reviewed-by: Athan Reines <[email protected]> Signed-off-by: Athan Reines <[email protected]>
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<!-- | ||
@license Apache-2.0 | ||
Copyright (c) 2024 The Stdlib Authors. | ||
Licensed under the Apache License, Version 2.0 (the "License"); | ||
you may not use this file except in compliance with the License. | ||
You may obtain a copy of the License at | ||
http://www.apache.org/licenses/LICENSE-2.0 | ||
Unless required by applicable law or agreed to in writing, software | ||
distributed under the License is distributed on an "AS IS" BASIS, | ||
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
See the License for the specific language governing permissions and | ||
limitations under the License. | ||
--> | ||
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# cscal | ||
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> Scales a single-precision complex floating-point vector by a single-precision complex floating-point constant. | ||
<section class="usage"> | ||
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## Usage | ||
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```javascript | ||
var cscal = require( '@stdlib/blas/base/cscal' ); | ||
``` | ||
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#### cscal( N, ca, cx, strideX ) | ||
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Scales values from `cx` by `ca`. | ||
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```javascript | ||
var Complex64Array = require( '@stdlib/array/complex64' ); | ||
var Complex64 = require( '@stdlib/complex/float32/ctor' ); | ||
var realf = require( '@stdlib/complex/realf' ); | ||
var imagf = require( '@stdlib/complex/imagf' ); | ||
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var cx = new Complex64Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] ); | ||
var ca = new Complex64( 2.0, 0.0 ); | ||
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cscal( 3, ca, cx, 1 ); | ||
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var z = cx.get( 0 ); | ||
// returns <Complex64> | ||
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var re = realf( z ); | ||
// returns 2.0 | ||
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var im = imagf( z ); | ||
// returns 2.0 | ||
``` | ||
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The function has the following parameters: | ||
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- **N**: number of indexed elements. | ||
- **ca**: scalar [`Complex64`][@stdlib/complex/float32/ctor] constant. | ||
- **cx**: input [`Complex64Array`][@stdlib/array/complex64]. | ||
- **strideX**: index increment for `cx`. | ||
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The `N` and stride parameters determine how values from `cx` are scaled by `ca`. For example, to scale every other value in `cx` by `ca`, | ||
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```javascript | ||
var Complex64Array = require( '@stdlib/array/complex64' ); | ||
var Complex64 = require( '@stdlib/complex/float32/ctor' ); | ||
var realf = require( '@stdlib/complex/realf' ); | ||
var imagf = require( '@stdlib/complex/imagf' ); | ||
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var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] ); | ||
var ca = new Complex64( 2.0, 0.0 ); | ||
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cscal( 2, ca, cx, 2 ); | ||
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var z = cx.get( 2 ); | ||
// returns <Complex64> | ||
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var re = realf( z ); | ||
// returns 10.0 | ||
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var im = imagf( z ); | ||
// returns 12.0 | ||
``` | ||
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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 | ||
var Complex64Array = require( '@stdlib/array/complex64' ); | ||
var Complex64 = require( '@stdlib/complex/float32/ctor' ); | ||
var realf = require( '@stdlib/complex/realf' ); | ||
var imagf = require( '@stdlib/complex/imagf' ); | ||
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// Initial array: | ||
var cx0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] ); | ||
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// Define a scalar constant: | ||
var ca = new Complex64( 2.0, 2.0 ); | ||
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// Create an offset view: | ||
var cx1 = new Complex64Array( cx0.buffer, cx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element | ||
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// Scales every other value from `cx1` by `ca`... | ||
cscal( 3, ca, cx1, 1 ); | ||
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var z = cx0.get( 1 ); | ||
// returns <Complex64> | ||
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var re = realf( z ); | ||
// returns -2.0 | ||
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var im = imagf( z ); | ||
// returns 14.0 | ||
``` | ||
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#### cscal.ndarray( N, ca, cx, strideX, offsetX ) | ||
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Scales values from `cx` by `ca` using alternative indexing semantics. | ||
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```javascript | ||
var Complex64Array = require( '@stdlib/array/complex64' ); | ||
var Complex64 = require( '@stdlib/complex/float32/ctor' ); | ||
var realf = require( '@stdlib/complex/realf' ); | ||
var imagf = require( '@stdlib/complex/imagf' ); | ||
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var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ); | ||
var ca = new Complex64( 2.0, 2.0 ); | ||
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cscal.ndarray( 3, ca, cx, 1, 0 ); | ||
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var z = cx.get( 0 ); | ||
// returns <Complex64> | ||
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var re = realf( z ); | ||
// returns -2.0 | ||
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var im = imagf( z ); | ||
// returns 6.0 | ||
``` | ||
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The function has the following additional parameters: | ||
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- **offsetX**: starting index for `cx`. | ||
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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 value in the input strided array starting from the second element, | ||
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```javascript | ||
var Complex64Array = require( '@stdlib/array/complex64' ); | ||
var Complex64 = require( '@stdlib/complex/float32/ctor' ); | ||
var realf = require( '@stdlib/complex/realf' ); | ||
var imagf = require( '@stdlib/complex/imagf' ); | ||
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var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] ); | ||
var ca = new Complex64( 2.0, 2.0 ); | ||
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cscal.ndarray( 2, ca, cx, 2, 1 ); | ||
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var z = cx.get( 3 ); | ||
// returns <Complex64> | ||
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var re = realf( z ); | ||
// returns -2.0 | ||
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var im = imagf( z ); | ||
// returns 30.0 | ||
``` | ||
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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` or `strideX <= 0` , both functions return `cx` unchanged. | ||
- `cscal()` corresponds to the [BLAS][blas] level 1 function [`cscal`][cscal]. | ||
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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 | ||
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ); | ||
var filledarrayBy = require( '@stdlib/array/filled-by' ); | ||
var Complex64 = require( '@stdlib/complex/float32/ctor' ); | ||
var cscal = require( '@stdlib/blas/base/cscal' ); | ||
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function rand() { | ||
return new Complex64( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) ); | ||
} | ||
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var cx = filledarrayBy( 10, 'complex64', rand ); | ||
console.log( cx.toString() ); | ||
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var ca = new Complex64( 2.0, 2.0 ); | ||
console.log( ca.toString() ); | ||
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// Scale elements from `cx` by `ca`: | ||
cscal( cx.length, ca, cx, 1 ); | ||
console.log( cx.get( cx.length-1 ).toString() ); | ||
``` | ||
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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 | ||
#include "stdlib/blas/base/cscal.h" | ||
``` | ||
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#### c_cscal( N, ca, \*CX, strideX ) | ||
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Scales values from `CX` by `ca`. | ||
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```c | ||
#include "stdlib/complex/float32/ctor.h" | ||
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float cx[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f }; | ||
const stdlib_complex64_t ca = stdlib_complex64( 2.0f, 2.0f ); | ||
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c_dscal( 4, ca, (void *)cx, 1 ); | ||
``` | ||
The function accepts the following arguments: | ||
- **N**: `[in] CBLAS_INT` number of indexed elements. | ||
- **ca**: `[in] stdlib_complex64_t` scalar constant. | ||
- **CX**: `[inout] void*` input array. | ||
- **strideX**: `[in] CBLAS_INT` index increment for `CX`. | ||
```c | ||
void c_dscal( const CBLAS_INT N, const stdlib_complex64_t ca, void *CX, const CBLAS_INT strideX ); | ||
``` | ||
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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 | ||
#include "stdlib/blas/base/cscal.h" | ||
#include "stdlib/complex/float32/ctor.h" | ||
#include <stdio.h> | ||
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int main( void ) { | ||
// Create a strided array of interleaved real and imaginary components: | ||
float cx[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f }; | ||
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// Create a complex scalar: | ||
const stdlib_complex64_t ca = stdlib_complex64( 2.0f, 2.0f ); | ||
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// Specify the number of elements: | ||
const int N = 4; | ||
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// Specify stride length: | ||
const int strideX = 1; | ||
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// Scale the elements of the array: | ||
c_cscal( N, ca, (void *)cx, strideX ); | ||
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// Print the result: | ||
for ( int i = 0; i < N; i++ ) { | ||
printf( "cx[ %i ] = %f + %fj\n", i, cx[ i*2 ], cx[ (i*2)+1 ] ); | ||
} | ||
} | ||
``` | ||
</section> | ||
<!-- /.examples --> | ||
</section> | ||
<!-- /.c --> | ||
<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. --> | ||
<section class="related"> | ||
</section> | ||
<!-- /.related --> | ||
<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> | ||
<section class="links"> | ||
[blas]: http://www.netlib.org/blas | ||
[cscal]: http://www.netlib.org/lapack/explore-html/da/df6/group__complex__blas__level1.html | ||
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray | ||
[@stdlib/array/complex64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex64 | ||
[@stdlib/complex/float32/ctor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/complex/float32/ctor | ||
</section> | ||
<!-- /.links --> |
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