time-to-botec

Benchmark sampling in different programming languages
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dnannsumkbn2.js (3016B)

      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 isnan = require( '@stdlib/math/base/assert/is-nan' );
     24 var abs = require( '@stdlib/math/base/special/abs' );
     25 
     26 
     27 // MAIN //
     28 
     29 /**
     30 * Computes the sum of double-precision floating-point strided array elements, ignoring `NaN` values and using a second-order iterative Kahan–Babuška algorithm.
     31 *
     32 * ## Method
     33 *
     34 * -   This implementation uses a second-order iterative Kahan–Babuška algorithm, as described by Klein (2005).
     35 *
     36 * ## References
     37 *
     38 * -   Klein, Andreas. 2005. "A Generalized Kahan-Babuška-Summation-Algorithm." _Computing_ 76 (3): 279–93. doi:[10.1007/s00607-005-0139-x](https://doi.org/10.1007/s00607-005-0139-x).
     39 *
     40 * @param {PositiveInteger} N - number of indexed elements
     41 * @param {Float64Array} x - input array
     42 * @param {integer} strideX - `x` stride length
     43 * @param {Float64Array} out - output array
     44 * @param {integer} strideOut - `out` stride length
     45 * @returns {Float64Array} output array
     46 *
     47 * @example
     48 * var Float64Array = require( '@stdlib/array/float64' );
     49 *
     50 * var x = new Float64Array( [ 1.0, -2.0, NaN, 2.0 ] );
     51 * var out = new Float64Array( 2 );
     52 *
     53 * var v = dnannsumkbn2( x.length, x, 1, out, 1 );
     54 * // returns <Float64Array>[ 1.0, 3 ]
     55 */
     56 function dnannsumkbn2( N, x, strideX, out, strideOut ) {
     57 	var sum;
     58 	var ccs;
     59 	var cs;
     60 	var cc;
     61 	var ix;
     62 	var io;
     63 	var v;
     64 	var t;
     65 	var c;
     66 	var n;
     67 	var i;
     68 
     69 	if ( strideX < 0 ) {
     70 		ix = (1-N) * strideX;
     71 	} else {
     72 		ix = 0;
     73 	}
     74 	if ( strideOut < 0 ) {
     75 		io = -strideOut;
     76 	} else {
     77 		io = 0;
     78 	}
     79 	sum = 0.0;
     80 	if ( N <= 0 ) {
     81 		out[ io ] = sum;
     82 		out[ io+strideOut ] = 0;
     83 		return out;
     84 	}
     85 	if ( N === 1 || strideX === 0 ) {
     86 		if ( isnan( x[ ix ] ) ) {
     87 			out[ io ] = sum;
     88 			out[ io+strideOut ] = 0;
     89 			return out;
     90 		}
     91 		out[ io ] = x[ ix ];
     92 		out[ io+strideOut ] = 1;
     93 		return out;
     94 	}
     95 	ccs = 0.0; // second order correction term for lost low order bits
     96 	cs = 0.0; // first order correction term for lost low order bits
     97 	n = 0;
     98 	for ( i = 0; i < N; i++ ) {
     99 		v = x[ ix ];
    100 		if ( isnan( v ) === false ) {
    101 			t = sum + v;
    102 			if ( abs( sum ) >= abs( v ) ) {
    103 				c = (sum-t) + v;
    104 			} else {
    105 				c = (v-t) + sum;
    106 			}
    107 			sum = t;
    108 			t = cs + c;
    109 			if ( abs( cs ) >= abs( c ) ) {
    110 				cc = (cs-t) + c;
    111 			} else {
    112 				cc = (c-t) + cs;
    113 			}
    114 			cs = t;
    115 			ccs += cc;
    116 			n += 1;
    117 		}
    118 		ix += strideX;
    119 	}
    120 	out[ io ] = sum + cs + ccs;
    121 	out[ io+strideOut ] = n;
    122 	return out;
    123 }
    124 
    125 
    126 // EXPORTS //
    127 
    128 module.exports = dnannsumkbn2;