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cwxsa

Subtract a scalar constant from each element in a single-precision complex floating-point strided array x and assign the results to elements in a single-precision complex floating-point strided array w.

This BLAS extension implements the operation

$$\mathbf{w} = \mathbf{x} - \alpha$$

This API is complementary to the package @stdlib/blas-ext/base/cxsa, which performs an in-place update.

Installation

npm install @stdlib/blas-ext-base-cwxsa

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var cwxsa = require( '@stdlib/blas-ext-base-cwxsa' );

cwxsa( N, alpha, x, strideX, w, strideW )

Subtracts a scalar constant from each element in a single-precision complex floating-point strided array x and assigns the results to elements in a single-precision complex floating-point strided array w.

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var w = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var alpha = new Complex64( 5.0, 3.0 );

cwxsa( x.length, alpha, x, 1, w, 1 );
// w => <Complex64Array>[ -4.0, -1.0, -2.0, 1.0, 0.0, 3.0, 2.0, 5.0 ]

The function has the following parameters:

• N: number of indexed elements.
• alpha: scalar constant.
• x: input Complex64Array.
• strideX: stride length for x.
• w: output Complex64Array.
• strideW: stride length for w.

The N and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to subtract alpha from every other element in x and assign the results to every other element in w:

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var w = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

var alpha = new Complex64( 5.0, 3.0 );

cwxsa( 2, alpha, x, 2, w, 2 );
// w => <Complex64Array>[ -4.0, -1.0, 0.0, 0.0, 0.0, 3.0, 0.0, 0.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

// Initial arrays...
var x0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var w0 = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Complex64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var w1 = new Complex64Array( w0.buffer, w0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

var alpha = new Complex64( 5.0, 3.0 );

cwxsa( 3, alpha, x1, 1, w1, 1 );
// w0 => <Complex64Array>[ 0.0, 0.0, 0.0, 0.0, -2.0, 1.0, 0.0, 3.0, 2.0, 5.0 ]

cwxsa.ndarray( N, alpha, x, strideX, offsetX, w, strideW, offsetW )

Subtracts a scalar constant from each element in a single-precision complex floating-point strided array x and assigns the results to elements in a single-precision complex floating-point strided array w using alternative indexing semantics.

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var w = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var alpha = new Complex64( 5.0, 3.0 );

cwxsa.ndarray( x.length, alpha, x, 1, 0, w, 1, 0 );
// w => <Complex64Array>[ -4.0, -1.0, -2.0, 1.0, 0.0, 3.0, 2.0, 5.0 ]

The function has the following additional parameters:

• offsetX: starting index for x.
• offsetW: starting index for w.

While 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 subtract alpha from the last three elements of x and assign the results to the last three elements of w:

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var w = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

var alpha = new Complex64( 5.0, 3.0 );

cwxsa.ndarray( 3, alpha, x, 1, x.length-3, w, 1, w.length-3 );
// w => <Complex64Array>[ 0.0, 0.0, 0.0, 0.0, 0.0, 3.0, 2.0, 5.0, 4.0, 7.0 ]

Notes

• If N <= 0, both functions return w unchanged.

Examples

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );
var logEach = require( '@stdlib/console-log-each' );
var cwxsa = require( '@stdlib/blas-ext-base-cwxsa' );

var xbuf = discreteUniform( 20, -100, 100, {
    'dtype': 'float32'
});
var wbuf = discreteUniform( 20, -100, 100, {
    'dtype': 'float32'
});
var x = new Complex64Array( xbuf.buffer );
var w = new Complex64Array( wbuf.buffer );
var alpha = new Complex64( 5.0, 3.0 );

cwxsa( x.length, alpha, x, 1, w, 1 );
logEach( '%s', w );

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C APIs

Usage

#include "stdlib/blas/ext/base/cwxsa.h"

stdlib_strided_cwxsa( N, alpha, *X, strideX, *W, strideW )

Subtracts a scalar constant from each element in a single-precision complex floating-point strided array X and assigns the results to elements in a single-precision complex floating-point strided array W.

#include "stdlib/complex/float32/ctor.h"

const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
float w[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
const stdlib_complex64_t alpha = stdlib_complex64( 5.0f, 3.0f );

stdlib_strided_cwxsa( 4, alpha, (const stdlib_complex64_t *)x, 1, (stdlib_complex64_t *)w, 1 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] stdlib_complex64_t scalar constant.
• X: [in] stdlib_complex64_t* input array.
• strideX: [in] CBLAS_INT stride length for X.
• W: [out] stdlib_complex64_t* output array.
• strideW: [in] CBLAS_INT stride length for W.

void stdlib_strided_cwxsa( const CBLAS_INT N, const stdlib_complex64_t alpha, const stdlib_complex64_t *X, const CBLAS_INT strideX, stdlib_complex64_t *W, const CBLAS_INT strideW );

stdlib_strided_cwxsa_ndarray( N, alpha, *X, strideX, offsetX, *W, strideW, offsetW )

Subtracts a scalar constant from each element in a single-precision complex floating-point strided array X and assigns the results to elements in a single-precision complex floating-point strided array W using alternative indexing semantics.

#include "stdlib/complex/float32/ctor.h"

const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
float w[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
const stdlib_complex64_t alpha = stdlib_complex64( 5.0f, 3.0f );

stdlib_strided_cwxsa_ndarray( 4, alpha, (const stdlib_complex64_t *)x, 1, 0, (stdlib_complex64_t *)w, 1, 0 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] stdlib_complex64_t scalar constant.
• X: [in] stdlib_complex64_t* input array.
• strideX: [in] CBLAS_INT stride length for X.
• offsetX: [in] CBLAS_INT starting index for X.
• W: [out] stdlib_complex64_t* output array.
• strideW: [in] CBLAS_INT stride length for W.
• offsetW: [in] CBLAS_INT starting index for W.

void stdlib_strided_cwxsa_ndarray( const CBLAS_INT N, const stdlib_complex64_t alpha, const stdlib_complex64_t *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, stdlib_complex64_t *W, const CBLAS_INT strideW, const CBLAS_INT offsetW );

Examples

#include "stdlib/blas/ext/base/cwxsa.h"
#include "stdlib/complex/float32/ctor.h"
#include "stdlib/complex/float32/real.h"
#include "stdlib/complex/float32/imag.h"
#include <stdio.h>

int main( void ) {
    // Create strided arrays:
    const stdlib_complex64_t x[] = {
        stdlib_complex64( 1.0f, 2.0f ),
        stdlib_complex64( 3.0f, 4.0f ),
        stdlib_complex64( 5.0f, 6.0f ),
        stdlib_complex64( 7.0f, 8.0f )
    };
    stdlib_complex64_t w[] = {
        stdlib_complex64( 0.0f, 0.0f ),
        stdlib_complex64( 0.0f, 0.0f ),
        stdlib_complex64( 0.0f, 0.0f ),
        stdlib_complex64( 0.0f, 0.0f )
    };

    // Specify the number of indexed elements:
    const int N = 4;

    // Specify strides:
    const int strideX = 1;
    const int strideW = 1;

    // Define a scalar constant:
    stdlib_complex64_t alpha = stdlib_complex64( 5.0f, 3.0f );

    // Subtract a constant from each element in `x` and assign to `w`:
    stdlib_strided_cwxsa( N, alpha, x, strideX, w, strideW );

    // Print the result:
    for ( int i = 0; i < N; i++ ) {
        printf( "w[ %i ] = %f + %fi\n", i, stdlib_complex64_real( w[ i ] ), stdlib_complex64_imag( w[ i ] ) );
    }
}

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Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.