All files / base/dwapx/lib ndarray.js

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/**
* @license Apache-2.0
*
* Copyright (c) 2026 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.
*/
 
'use strict';
 
// MODULES //
 
var dcopy = require( '@stdlib/blas/base/dcopy' ).ndarray;
 
 
// VARIABLES //
 
var M = 5;
 
 
// MAIN //
 
/**
* Adds a scalar constant to each element in a double-precision floating-point strided array `x` and assigns the results to elements in a double-precision floating-point strided array `w` using alternative indexing semantics.
*
* @param {PositiveInteger} N - number of indexed elements
* @param {number} alpha - scalar constant
* @param {Float64Array} x - input array
* @param {integer} strideX - `x` stride length
* @param {NonNegativeInteger} offsetX - starting `x` index
* @param {Float64Array} w - output array
* @param {integer} strideW - `w` stride length
* @param {NonNegativeInteger} offsetW - starting `w` index
* @returns {Float64Array} output array
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
* var w = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );
*
* dwapx( x.length, 5.0, x, 1, 0, w, 1, 0 );
* // w => <Float64Array>[ 6.0, 7.0, 8.0, 9.0, 10.0 ]
*/
function dwapx( N, alpha, x, strideX, offsetX, w, strideW, offsetW ) {
	var ix;
	var iw;
	var m;
	var i;

	if ( N <= 0 ) {
		return w;
	}
	// Fast path: when alpha = 0.0, delegate to dcopy (w = x)
	if ( alpha === 0.0 ) {
		return dcopy( N, x, strideX, offsetX, w, strideW, offsetW );
	}
	ix = offsetX;
	iw = offsetW;

	// Use loop unrolling if both strides are equal to `1`...
	if ( strideX === 1 && strideW === 1 ) {
		m = N % M;

		// If we have a remainder, run a clean-up loop...
		if ( m > 0 ) {
			for ( i = 0; i < m; i++ ) {
				w[ iw ] = x[ ix ] + alpha;
				ix += strideX;
				iw += strideW;
			}
		}
		if ( N < M ) {
			return w;
		}
		for ( i = m; i < N; i += M ) {
			w[ iw ] = x[ ix ] + alpha;
			w[ iw+1 ] = x[ ix+1 ] + alpha;
			w[ iw+2 ] = x[ ix+2 ] + alpha;
			w[ iw+3 ] = x[ ix+3 ] + alpha;
			w[ iw+4 ] = x[ ix+4 ] + alpha;
			ix += M;
			iw += M;
		}
		return w;
	}
	for ( i = 0; i < N; i++ ) {
		w[ iw ] = x[ ix ] + alpha;
		ix += strideX;
		iw += strideW;
	}
	return w;
}
 
 
// EXPORTS //
 
module.exports = dwapx;