time-to-botec

Benchmark sampling in different programming languages
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snansumpw.js (2266B)

      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 float64ToFloat32 = require( '@stdlib/number/float64/base/to-float32' );
     24 var isnanf = require( '@stdlib/math/base/assert/is-nanf' );
     25 var sum = require( './ndarray.js' );
     26 
     27 
     28 // MAIN //
     29 
     30 /**
     31 * Computes the sum of single-precision floating-point strided array elements, ignoring `NaN` values and using pairwise summation.
     32 *
     33 * ## Method
     34 *
     35 * -   This implementation uses pairwise summation, which accrues rounding error `O(log2 N)` instead of `O(N)`. The recursion depth is also `O(log2 N)`.
     36 *
     37 * ## References
     38 *
     39 * -   Higham, Nicholas J. 1993. "The Accuracy of Floating Point Summation." _SIAM Journal on Scientific Computing_ 14 (4): 783–99. doi:[10.1137/0914050](https://doi.org/10.1137/0914050).
     40 *
     41 * @param {PositiveInteger} N - number of indexed elements
     42 * @param {Float32Array} x - input array
     43 * @param {integer} stride - stride length
     44 * @returns {number} sum
     45 *
     46 * @example
     47 * var Float32Array = require( '@stdlib/array/float32' );
     48 *
     49 * var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );
     50 * var N = x.length;
     51 *
     52 * var v = snansumpw( N, x, 1 );
     53 * // returns 1.0
     54 */
     55 function snansumpw( N, x, stride ) {
     56 	var ix;
     57 	var s;
     58 	var i;
     59 
     60 	if ( N <= 0 ) {
     61 		return 0.0;
     62 	}
     63 	if ( N === 1 || stride === 0 ) {
     64 		if ( isnanf( x[ 0 ] ) ) {
     65 			return 0.0;
     66 		}
     67 		return x[ 0 ];
     68 	}
     69 	if ( stride < 0 ) {
     70 		ix = (1-N) * stride;
     71 	} else {
     72 		ix = 0;
     73 	}
     74 	if ( N < 8 ) {
     75 		// Use simple summation...
     76 		s = 0.0;
     77 		for ( i = 0; i < N; i++ ) {
     78 			if ( isnanf( x[ ix ] ) === false ) {
     79 				s = float64ToFloat32( s + x[ ix ] );
     80 			}
     81 			ix += stride;
     82 		}
     83 		return s;
     84 	}
     85 	return sum( N, x, stride, ix );
     86 }
     87 
     88 
     89 // EXPORTS //
     90 
     91 module.exports = snansumpw;