All files / gaxpb/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 arraylike2object = require( '@stdlib/array/base/arraylike2object' );
var gapx = require( '@stdlib/blas/ext/base/gapx' ).ndarray;
var gscal = require( '@stdlib/blas/base/gscal' ).ndarray;
var accessors = require( './accessors.js' );
 
 
// VARIABLES //
 
var M = 5;
 
 
// MAIN //
 
/**
* Multiplies each element in a strided array by a scalar constant and adds a scalar constant to each result.
*
* @param {PositiveInteger} N - number of indexed elements
* @param {number} alpha - first scalar constant
* @param {number} beta - second scalar constant
* @param {NumericArray} x - input array
* @param {integer} strideX - stride length
* @param {NonNegativeInteger} offsetX - starting index
* @returns {NumericArray} input array
*
* @example
* var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];
*
* gaxpb( 3, 5.0, 3.0, x, 1, x.length-3 );
* // x => [ 1.0, -2.0, 3.0, -17.0, 28.0, -27.0 ]
*/
function gaxpb( N, alpha, beta, x, strideX, offsetX ) {
	var ix;
	var m;
	var o;
	var i;

	if ( N <= 0 ) {
		return x;
	}
	// Fast path: when alpha = 1.0, delegate to gapx (x = x + beta)
	if ( alpha === 1.0 ) {
		return gapx( N, beta, x, strideX, offsetX );
	}
	// Fast path: when beta = 0.0, delegate to gscal (x = alpha * x)
	if ( beta === 0.0 ) {
		return gscal( N, alpha, x, strideX, offsetX );
	}
	o = arraylike2object( x );
	if ( o.accessorProtocol ) {
		return accessors( N, alpha, beta, o, strideX, offsetX );
	}
	ix = offsetX;

	// Use loop unrolling if the stride is equal to `1`...
	if ( strideX === 1 ) {
		m = N % M;

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