time-to-botec

Benchmark sampling in different programming languages
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README.md (4304B)

      1 <!--
      2 
      3 @license Apache-2.0
      4 
      5 Copyright (c) 2020 The Stdlib Authors.
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      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
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     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.
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     19 -->
     20 
     21 # gsum
     22 
     23 > Calculate the sum of strided array elements.
     24 
     25 <section class="intro">
     26 
     27 </section>
     28 
     29 <!-- /.intro -->
     30 
     31 <section class="usage">
     32 
     33 ## Usage
     34 
     35 ```javascript
     36 var gsum = require( '@stdlib/blas/ext/base/gsum' );
     37 ```
     38 
     39 #### gsum( N, x, stride )
     40 
     41 Computes the sum of strided array elements.
     42 
     43 ```javascript
     44 var x = [ 1.0, -2.0, 2.0 ];
     45 var N = x.length;
     46 
     47 var v = gsum( N, x, 1 );
     48 // returns 1.0
     49 ```
     50 
     51 The function has the following parameters:
     52 
     53 -   **N**: number of indexed elements.
     54 -   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
     55 -   **stride**: index increment for `x`.
     56 
     57 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`,
     58 
     59 ```javascript
     60 var floor = require( '@stdlib/math/base/special/floor' );
     61 
     62 var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ];
     63 var N = floor( x.length / 2 );
     64 
     65 var v = gsum( N, x, 2 );
     66 // returns 5.0
     67 ```
     68 
     69 Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
     70 
     71 <!-- eslint-disable stdlib/capitalized-comments -->
     72 
     73 ```javascript
     74 var Float64Array = require( '@stdlib/array/float64' );
     75 var floor = require( '@stdlib/math/base/special/floor' );
     76 
     77 var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
     78 var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
     79 
     80 var N = floor( x0.length / 2 );
     81 
     82 var v = gsum( N, x1, 2 );
     83 // returns 5.0
     84 ```
     85 
     86 #### gsum.ndarray( N, x, stride, offset )
     87 
     88 Computes the sum of strided array elements using alternative indexing semantics.
     89 
     90 ```javascript
     91 var x = [ 1.0, -2.0, 2.0 ];
     92 var N = x.length;
     93 
     94 var v = gsum.ndarray( N, x, 1, 0 );
     95 // returns 1.0
     96 ```
     97 
     98 The function has the following additional parameters:
     99 
    100 -   **offset**: starting index for `x`.
    101 
    102 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
    103 
    104 ```javascript
    105 var floor = require( '@stdlib/math/base/special/floor' );
    106 
    107 var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];
    108 var N = floor( x.length / 2 );
    109 
    110 var v = gsum.ndarray( N, x, 2, 1 );
    111 // returns 5.0
    112 ```
    113 
    114 </section>
    115 
    116 <!-- /.usage -->
    117 
    118 <section class="notes">
    119 
    120 ## Notes
    121 
    122 -   If `N <= 0`, both functions return `0.0`.
    123 -   Depending on the environment, the typed versions ([`dsum`][@stdlib/blas/ext/base/dsum], [`ssum`][@stdlib/blas/ext/base/ssum], etc.) are likely to be significantly more performant.
    124 
    125 </section>
    126 
    127 <!-- /.notes -->
    128 
    129 <section class="examples">
    130 
    131 ## Examples
    132 
    133 <!-- eslint no-undef: "error" -->
    134 
    135 ```javascript
    136 var randu = require( '@stdlib/random/base/randu' );
    137 var round = require( '@stdlib/math/base/special/round' );
    138 var Float64Array = require( '@stdlib/array/float64' );
    139 var gsum = require( '@stdlib/blas/ext/base/gsum' );
    140 
    141 var x;
    142 var i;
    143 
    144 x = new Float64Array( 10 );
    145 for ( i = 0; i < x.length; i++ ) {
    146     x[ i ] = round( randu()*100.0 );
    147 }
    148 console.log( x );
    149 
    150 var v = gsum( x.length, x, 1 );
    151 console.log( v );
    152 ```
    153 
    154 </section>
    155 
    156 <!-- /.examples -->
    157 
    158 <section class="references">
    159 
    160 </section>
    161 
    162 <!-- /.references -->
    163 
    164 <section class="links">
    165 
    166 [mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
    167 
    168 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
    169 
    170 [@stdlib/blas/ext/base/dsum]: https://www.npmjs.com/package/@stdlib/blas/tree/main/ext/base/dsum
    171 
    172 [@stdlib/blas/ext/base/ssum]: https://www.npmjs.com/package/@stdlib/blas/tree/main/ext/base/ssum
    173 
    174 </section>
    175 
    176 <!-- /.links -->