83 lines
1.7 KiB
JavaScript
83 lines
1.7 KiB
JavaScript
/**
|
|
* @license Apache-2.0
|
|
*
|
|
* Copyright (c) 2020 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';
|
|
|
|
// VARIABLES //
|
|
|
|
var M = 5;
|
|
|
|
|
|
// MAIN //
|
|
|
|
/**
|
|
* Multiplies `x` by a scalar `alpha`.
|
|
*
|
|
* @param {PositiveInteger} N - number of indexed elements
|
|
* @param {number} alpha - scalar
|
|
* @param {NumericArray} x - input array
|
|
* @param {PositiveInteger} stride - index increment
|
|
* @returns {NumericArray} input array
|
|
*
|
|
* @example
|
|
* var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
|
|
*
|
|
* gscal( x.length, 5.0, x, 1 );
|
|
* // x => [ -10.0, 5.0, 15.0, -25.0, 20.0, 0.0, -5.0, -15.0 ]
|
|
*/
|
|
function gscal( N, alpha, x, stride ) {
|
|
var m;
|
|
var i;
|
|
|
|
if ( N <= 0 || stride <= 0|| alpha === 1.0 ) {
|
|
return x;
|
|
}
|
|
// Use loop unrolling if the stride is equal to `1`...
|
|
if ( stride === 1 ) {
|
|
m = N % M;
|
|
|
|
// If we have a remainder, run a clean-up loop...
|
|
if ( m > 0 ) {
|
|
for ( i = 0; i < m; i += 1 ) {
|
|
x[ i ] *= alpha;
|
|
}
|
|
}
|
|
if ( N < M ) {
|
|
return x;
|
|
}
|
|
for ( i = m; i < N; i += M ) {
|
|
x[ i ] *= alpha;
|
|
x[ i+1 ] *= alpha;
|
|
x[ i+2 ] *= alpha;
|
|
x[ i+3 ] *= alpha;
|
|
x[ i+4 ] *= alpha;
|
|
}
|
|
return x;
|
|
}
|
|
N *= stride;
|
|
for ( i = 0; i < N; i += stride ) {
|
|
x[ i ] *= alpha;
|
|
}
|
|
return x;
|
|
}
|
|
|
|
|
|
// EXPORTS //
|
|
|
|
module.exports = gscal;
|