README.md (5091B)
1 <!-- 2 3 @license Apache-2.0 4 5 Copyright (c) 2020 The Stdlib Authors. 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18 19 --> 20 21 # dsnansumpw 22 23 > Calculate the sum of single-precision floating-point strided array elements, ignoring `NaN` values, using pairwise summation with extended accumulation, and returning an extended precision result. 24 25 <section class="intro"> 26 27 </section> 28 29 <!-- /.intro --> 30 31 <section class="usage"> 32 33 ## Usage 34 35 ```javascript 36 var dsnansumpw = require( '@stdlib/blas/ext/base/dsnansumpw' ); 37 ``` 38 39 #### dsnansumpw( N, x, stride ) 40 41 Computes the sum of single-precision floating-point strided array elements, ignoring `NaN` values, using pairwise summation with extended accumulation, and returning an extended precision result. 42 43 ```javascript 44 var Float32Array = require( '@stdlib/array/float32' ); 45 46 var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] ); 47 var N = x.length; 48 49 var v = dsnansumpw( N, x, 1 ); 50 // returns 1.0 51 ``` 52 53 The function has the following parameters: 54 55 - **N**: number of indexed elements. 56 - **x**: input [`Float32Array`][@stdlib/array/float32]. 57 - **stride**: index increment for `x`. 58 59 The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to compute the sum of every other element in `x`, 60 61 ```javascript 62 var Float32Array = require( '@stdlib/array/float32' ); 63 var floor = require( '@stdlib/math/base/special/floor' ); 64 65 var x = new Float32Array( [ 1.0, 2.0, NaN, -7.0, NaN, 3.0, 4.0, 2.0 ] ); 66 var N = floor( x.length / 2 ); 67 68 var v = dsnansumpw( N, x, 2 ); 69 // returns 5.0 70 ``` 71 72 Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. 73 74 <!-- eslint-disable stdlib/capitalized-comments --> 75 76 ```javascript 77 var Float32Array = require( '@stdlib/array/float32' ); 78 var floor = require( '@stdlib/math/base/special/floor' ); 79 80 var x0 = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); 81 var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element 82 83 var N = floor( x0.length / 2 ); 84 85 var v = dsnansumpw( N, x1, 2 ); 86 // returns 5.0 87 ``` 88 89 #### dsnansumpw.ndarray( N, x, stride, offset ) 90 91 Computes the sum of single-precision floating-point strided array elements, ignoring `NaN` values and using pairwise summation with extended accumulation and alternative indexing semantics. 92 93 ```javascript 94 var Float32Array = require( '@stdlib/array/float32' ); 95 96 var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] ); 97 var N = x.length; 98 99 var v = dsnansumpw.ndarray( N, x, 1, 0 ); 100 // returns 1.0 101 ``` 102 103 The function has the following additional parameters: 104 105 - **offset**: starting index for `x`. 106 107 While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the sum of every other value in `x` starting from the second value 108 109 ```javascript 110 var Float32Array = require( '@stdlib/array/float32' ); 111 var floor = require( '@stdlib/math/base/special/floor' ); 112 113 var x = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); 114 var N = floor( x.length / 2 ); 115 116 var v = dsnansumpw.ndarray( N, x, 2, 1 ); 117 // returns 5.0 118 ``` 119 120 </section> 121 122 <!-- /.usage --> 123 124 <section class="notes"> 125 126 ## Notes 127 128 - If `N <= 0`, both functions return `0.0`. 129 - Accumulated intermediate values are stored as double-precision floating-point numbers. 130 131 </section> 132 133 <!-- /.notes --> 134 135 <section class="examples"> 136 137 ## Examples 138 139 <!-- eslint no-undef: "error" --> 140 141 ```javascript 142 var randu = require( '@stdlib/random/base/randu' ); 143 var round = require( '@stdlib/math/base/special/round' ); 144 var Float32Array = require( '@stdlib/array/float32' ); 145 var dsnansumpw = require( '@stdlib/blas/ext/base/dsnansumpw' ); 146 147 var x; 148 var i; 149 150 x = new Float32Array( 10 ); 151 for ( i = 0; i < x.length; i++ ) { 152 if ( randu() < 0.2 ) { 153 x[ i ] = NaN; 154 } else { 155 x[ i ] = round( randu()*100.0 ); 156 } 157 } 158 console.log( x ); 159 160 var v = dsnansumpw( x.length, x, 1 ); 161 console.log( v ); 162 ``` 163 164 </section> 165 166 <!-- /.examples --> 167 168 * * * 169 170 <section class="references"> 171 172 ## References 173 174 - Higham, Nicholas J. 1993. "The Accuracy of Floating Point Summation." _SIAM Journal on Scientific Computing_ 14 (4): 783–99. doi:[10.1137/0914050][@higham:1993a]. 175 176 </section> 177 178 <!-- /.references --> 179 180 <section class="links"> 181 182 [@stdlib/array/float32]: https://www.npmjs.com/package/@stdlib/array-float32 183 184 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray 185 186 [@higham:1993a]: https://doi.org/10.1137/0914050 187 188 </section> 189 190 <!-- /.links -->