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| /** | ||
| * @license Apache-2.0 | ||
| * | ||
| * Copyright (c) 2025 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. | ||
| */ | ||
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| 'use strict'; | ||
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| // MODULES // | ||
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| var isnan = require( '@stdlib/math/base/assert/is-nan' ); | ||
| var abs = require( '@stdlib/math/base/special/abs' ); | ||
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| // MAIN // | ||
|
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| /** | ||
| * Computes the sum of strided array elements, ignoring `NaN` values and using an improved Kahan–Babuška algorithm. | ||
| * | ||
| * ## Method | ||
| * | ||
| * - This implementation uses an "improved Kahan–Babuška algorithm", as described by Neumaier (1974). | ||
| * | ||
| * ## References | ||
| * | ||
| * - Neumaier, Arnold. 1974. "Rounding Error Analysis of Some Methods for Summing Finite Sums." _Zeitschrift Für Angewandte Mathematik Und Mechanik_ 54 (1): 39–51. doi:[10.1002/zamm.19740540106](https://doi.org/10.1002/zamm.19740540106). | ||
| * | ||
| * @private | ||
| * @param {PositiveInteger} N - number of indexed elements | ||
| * @param {Object} x - input array object | ||
| * @param {Collection} x.data - input array data | ||
| * @param {Array<Function>} x.accessors - array element accessors | ||
| * @param {integer} strideX - stride length for `x` | ||
| * @param {NonNegativeInteger} offsetX - starting index for `x` | ||
| * @param {Object} out - output array object | ||
| * @param {Collection} out.data - output array data | ||
| * @param {Array<Function>} out.accessors - array element accessors | ||
| * @param {integer} strideOut - stride length for `out` | ||
| * @param {NonNegativeInteger} offsetOut - starting index for `out` | ||
| * @returns {Object} output array object | ||
| * | ||
| * @example | ||
| * var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' ); | ||
| * var arraylike2object = require( '@stdlib/array/base/arraylike2object' ); | ||
| * | ||
| * var x = toAccessorArray( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0, NaN, NaN ] ); | ||
| * var out = toAccessorArray( [ 0.0, 0 ] ); | ||
| * | ||
| * var v = gnannsumkbn( 5, arraylike2object( x ), 2, 1, arraylike2object( out ), 1, 0 ); | ||
| * // returns {...} | ||
| */ | ||
| function gnannsumkbn( N, x, strideX, offsetX, out, strideOut, offsetOut ) { | ||
| var obuf; | ||
| var xbuf; | ||
| var xget; | ||
| var oset; | ||
| var sum; | ||
| var ix; | ||
| var v; | ||
| var t; | ||
| var c; | ||
| var n; | ||
| var i; | ||
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| // Cache reference to array data: | ||
| xbuf = x.data; | ||
| obuf = out.data; | ||
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| // Cache reference to the element accessors: | ||
| xget = x.accessors[ 0 ]; | ||
| oset = out.accessors[ 1 ]; | ||
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| sum = 0.0; | ||
| ix = offsetX; | ||
| if ( strideX === 0 ) { | ||
| v = xget( xbuf, ix ); | ||
| if ( isnan( v ) ) { | ||
| oset( obuf, offsetOut, sum ); | ||
| oset( obuf, offsetOut+strideOut, 0 ); | ||
| return out; | ||
| } | ||
| oset( obuf, offsetOut, v * N ); | ||
| oset( obuf, offsetOut+strideOut, N ); | ||
| return out; | ||
| } | ||
| c = 0.0; | ||
| n = 0; | ||
| for ( i = 0; i < N; i++ ) { | ||
| v = xget( xbuf, ix ); | ||
| if ( isnan( v ) === false ) { | ||
| t = sum + v; | ||
| if ( abs( sum ) >= abs( v ) ) { | ||
| c += (sum-t) + v; | ||
| } else { | ||
| c += (v-t) + sum; | ||
| } | ||
| sum = t; | ||
| n += 1; | ||
| } | ||
| ix += strideX; | ||
| } | ||
| oset( obuf, offsetOut, sum + c ); | ||
| oset( obuf, offsetOut+strideOut, n ); | ||
| return out; | ||
| } | ||
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| // EXPORTS // | ||
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| module.exports = gnannsumkbn; |
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