time-to-botec

Benchmark sampling in different programming languages
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README.md (3185B)

      1 <!--
      2 
      3 @license Apache-2.0
      4 
      5 Copyright (c) 2018 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
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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 # Normalize
     22 
     23 > Return a normal number `y` and exponent `exp` satisfying `x = y * 2^exp`.
     24 
     25 <section class="usage">
     26 
     27 ## Usage
     28 
     29 ```javascript
     30 var normalize = require( '@stdlib/number/float64/base/normalize' );
     31 ```
     32 
     33 #### normalize( \[out,] x )
     34 
     35 Returns a normal number `y` and exponent `exp` satisfying `x = y * 2^exp`.
     36 
     37 ```javascript
     38 var out = normalize( 3.14e-319 );
     39 // returns [ 1.4141234400356668e-303, -52 ]
     40 ```
     41 
     42 By default, the function returns `y` and `exp` as a two-element `array`.
     43 
     44 ```javascript
     45 var pow = require( '@stdlib/math/base/special/pow' );
     46 
     47 var out = normalize( 3.14e-319 );
     48 // returns [ 1.4141234400356668e-303, -52 ]
     49 
     50 var y = out[ 0 ];
     51 var exp = out[ 1 ];
     52 
     53 var bool = ( y*pow(2.0, exp) === 3.14e-319 );
     54 // returns true
     55 ```
     56 
     57 To avoid unnecessary memory allocation, the function supports providing an output (destination) object.
     58 
     59 ```javascript
     60 var Float64Array = require( '@stdlib/array/float64' );
     61 
     62 var out = new Float64Array( 2 );
     63 
     64 var v = normalize( out, 3.14e-319 );
     65 // returns <Float64Array>[ 1.4141234400356668e-303, -52 ]
     66 
     67 var bool = ( v === out );
     68 // returns true
     69 ```
     70 
     71 The function expects a finite, non-zero `numeric` value `x`. If `x == 0`,
     72 
     73 ```javascript
     74 var out = normalize( 0.0 );
     75 // returns [ 0.0, 0 ];
     76 ```
     77 
     78 If `x` is either positive or negative `infinity` or `NaN`,
     79 
     80 ```javascript
     81 var PINF = require( '@stdlib/constants/float64/pinf' );
     82 var NINF = require( '@stdlib/constants/float64/ninf' );
     83 
     84 var out = normalize( PINF );
     85 // returns [ Infinity, 0 ]
     86 
     87 out = normalize( NINF );
     88 // returns [ -Infinity, 0 ]
     89 
     90 out = normalize( NaN );
     91 // returns [ NaN, 0 ]
     92 ```
     93 
     94 </section>
     95 
     96 <!-- /.usage -->
     97 
     98 <section class="examples">
     99 
    100 ## Examples
    101 
    102 <!-- eslint no-undef: "error" -->
    103 
    104 ```javascript
    105 var randu = require( '@stdlib/random/base/randu' );
    106 var round = require( '@stdlib/math/base/special/round' );
    107 var pow = require( '@stdlib/math/base/special/pow' );
    108 var normalize = require( '@stdlib/number/float64/base/normalize' );
    109 
    110 var frac;
    111 var exp;
    112 var x;
    113 var v;
    114 var i;
    115 
    116 // Generate denormalized numbers and then normalize them...
    117 for ( i = 0; i < 100; i++ ) {
    118     // Generate a random fraction:
    119     frac = randu() * 10.0;
    120 
    121     // Generate an exponent on the interval (-308,-324):
    122     exp = -309 - round( randu()*14.0 );
    123 
    124     // Create a subnormal number (~2.23e-308, ~4.94e-324):
    125     x = frac * pow( 10.0, exp );
    126 
    127     // Determine a `y` and an `exp` to "normalize" the subnormal:
    128     v = normalize( x );
    129 
    130     console.log( '%d = %d * 2^%d = %d', x, v[0], v[1], v[0]*pow(2.0, v[1]) );
    131 }
    132 ```
    133 
    134 </section>
    135 
    136 <!-- /.examples -->
    137 
    138 <section class="links">
    139 
    140 </section>
    141 
    142 <!-- /.links -->