time-to-botec

Benchmark sampling in different programming languages
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sscal.js (1876B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2019 The Stdlib Authors.
      5 *
      6 * Licensed under the Apache License, Version 2.0 (the "License");
      7 * you may not use this file except in compliance with the License.
      8 * You may obtain a copy of the License at
      9 *
     10 *    http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing, software
     13 * distributed under the License is distributed on an "AS IS" BASIS,
     14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15 * See the License for the specific language governing permissions and
     16 * limitations under the License.
     17 */
     18 
     19 'use strict';
     20 
     21 // VARIABLES //
     22 
     23 var M = 5;
     24 
     25 
     26 // MAIN //
     27 
     28 /**
     29 * Multiplies a vector `x` by a scalar `alpha`.
     30 *
     31 * @param {PositiveInteger} N - number of indexed elements
     32 * @param {number} alpha - scalar
     33 * @param {Float32Array} x - input array
     34 * @param {PositiveInteger} stride - index increment
     35 * @returns {Float32Array} input array
     36 *
     37 * @example
     38 * var Float32Array = require( '@stdlib/array/float32' );
     39 *
     40 * var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
     41 *
     42 * sscal( x.length, 5.0, x, 1 );
     43 * // x => <Float32Array>[ -10.0, 5.0, 15.0, -25.0, 20.0, 0.0, -5.0, -15.0 ]
     44 */
     45 function sscal( N, alpha, x, stride ) {
     46 	var i;
     47 	var m;
     48 
     49 	if ( N <= 0 || stride <= 0|| alpha === 1.0 ) {
     50 		return x;
     51 	}
     52 	// Use loop unrolling if the stride is equal to `1`...
     53 	if ( stride === 1 ) {
     54 		m = N % M;
     55 
     56 		// If we have a remainder, run a clean-up loop...
     57 		if ( m > 0 ) {
     58 			for ( i = 0; i < m; i++ ) {
     59 				x[ i ] *= alpha;
     60 			}
     61 		}
     62 		if ( N < M ) {
     63 			return x;
     64 		}
     65 		for ( i = m; i < N; i += M ) {
     66 			x[ i ] *= alpha;
     67 			x[ i+1 ] *= alpha;
     68 			x[ i+2 ] *= alpha;
     69 			x[ i+3 ] *= alpha;
     70 			x[ i+4 ] *= alpha;
     71 		}
     72 		return x;
     73 	}
     74 	N *= stride;
     75 	for ( i = 0; i < N; i += stride ) {
     76 		x[ i ] *= alpha;
     77 	}
     78 	return x;
     79 }
     80 
     81 
     82 // EXPORTS //
     83 
     84 module.exports = sscal;