@stdlib/blas-ext-base-gfill NPM

gfill

Fill a strided array with a specified scalar constant.

Installation

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

Usage

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

gfill( N, alpha, x, stride )

Fills a strided array x with a specified scalar constant alpha.

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];

gfill( x.length, 5.0, x, 1 );
// x => [ 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 ]

The function has the following parameters:

N: number of indexed elements.
alpha: scalar constant.
x: input array.
stride: index increment.

The N and stride parameters determine which elements in x are accessed at runtime. For example, to fill every other element

var floor = require( '@stdlib/math-base-special-floor' );

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
var N = floor( x.length / 2 );

gfill( N, 5.0, x, 2 );
// x => [ 5.0, 1.0, 5.0, -5.0, 5.0, 0.0, 5.0, -3.0 ]

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

var Float64Array = require( '@stdlib/array-float64' );
var floor = require( '@stdlib/math-base-special-floor' );

// Initial array...
var x0 = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var N = floor( x0.length/2 );

// Fill every other element...
gfill( N, 5.0, x1, 2 );
// x0 => <Float64Array>[ 1.0, 5.0, 3.0, 5.0, 5.0, 5.0 ]

gfill.ndarray( N, alpha, x, stride, offset )

Fills a strided array x with a specified scalar constant alpha using alternative indexing semantics.

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];

gfill.ndarray( x.length, 5.0, x, 1, 0 );
// x => [ 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 ]

The function has the following additional parameters:

offset: starting index.

While 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 of x

var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];

gfill.ndarray( 3, 5.0, x, 1, x.length-3 );
// x => [ 1.0, -2.0, 3.0, 5.0, 5.0, 5.0 ]

Notes

If N <= 0, both functions return x unchanged.
Both functions support array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array-complex64).
Depending on the environment, the typed versions (dfill, sfill, etc.) are likely to be significantly more performant.

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var Float64Array = require( '@stdlib/array-float64' );
var gfill = require( '@stdlib/blas-ext-base-gfill' );

var x = new Float64Array( 10 );
var i;
for ( i = 0; i < x.length; i++ ) {
    x[ i ] = discreteUniform( -100, 100 );
}
console.log( x );

gfill( x.length, 5.0, x, 1 );
console.log( x );

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.