time-to-botec

Benchmark sampling in different programming languages
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ndarray.js (2148B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2020 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 // MODULES //
     22 
     23 var floor = require( '@stdlib/math/base/special/floor' );
     24 
     25 
     26 // VARIABLES //
     27 
     28 var M = 3;
     29 
     30 
     31 // MAIN //
     32 
     33 /**
     34 * Reverses a strided array in-place.
     35 *
     36 * @param {PositiveInteger} N - number of indexed elements
     37 * @param {NumericArray} x - input array
     38 * @param {integer} stride - index increment
     39 * @param {NonNegativeInteger} offset - starting index
     40 * @returns {NumericArray} input array
     41 *
     42 * @example
     43 * var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];
     44 *
     45 * grev( 3, x, 1, x.length-3 );
     46 * // x => [ 1.0, -2.0, 3.0, -6.0, 5.0, -4.0 ]
     47 */
     48 function grev( N, x, stride, offset ) {
     49 	var tmp;
     50 	var ix;
     51 	var iy;
     52 	var m;
     53 	var n;
     54 	var i;
     55 
     56 	if ( N <= 0 ) {
     57 		return x;
     58 	}
     59 	n = floor( N/2 );
     60 	ix = offset;
     61 
     62 	// Use loop unrolling if the stride is equal to `1`...
     63 	if ( stride === 1 ) {
     64 		m = n % M;
     65 		iy = ix + N - 1;
     66 
     67 		// If we have a remainder, run a clean-up loop...
     68 		if ( m > 0 ) {
     69 			for ( i = 0; i < m; i++ ) {
     70 				tmp = x[ ix ];
     71 				x[ ix ] = x[ iy ];
     72 				x[ iy ] = tmp;
     73 				ix += stride;
     74 				iy -= stride;
     75 			}
     76 		}
     77 		if ( n < M ) {
     78 			return x;
     79 		}
     80 		for ( i = m; i < n; i += M ) {
     81 			tmp = x[ ix ];
     82 			x[ ix ] = x[ iy ];
     83 			x[ iy ] = tmp;
     84 
     85 			tmp = x[ ix+1 ];
     86 			x[ ix+1 ] = x[ iy-1 ];
     87 			x[ iy-1 ] = tmp;
     88 
     89 			tmp = x[ ix+2 ];
     90 			x[ ix+2 ] = x[ iy-2 ];
     91 			x[ iy-2 ] = tmp;
     92 
     93 			ix += M;
     94 			iy -= M;
     95 		}
     96 		return x;
     97 	}
     98 	iy = ix + ((N-1)*stride);
     99 	for ( i = 0; i < n; i++ ) {
    100 		tmp = x[ ix ];
    101 		x[ ix ] = x[ iy ];
    102 		x[ iy ] = tmp;
    103 		ix += stride;
    104 		iy -= stride;
    105 	}
    106 	return x;
    107 }
    108 
    109 
    110 // EXPORTS //
    111 
    112 module.exports = grev;