time-to-botec

Benchmark sampling in different programming languages
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cinv.js (2117B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2018 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 abs = require( './../../../../base/special/abs' );
     24 var max = require( './../../../../base/special/max' );
     25 var FLOAT64_BIGGEST = require( '@stdlib/constants/float64/max' );
     26 var FLOAT64_SMALLEST = require( '@stdlib/constants/float64/smallest-normal' );
     27 var EPS = require( '@stdlib/constants/float64/eps' );
     28 
     29 
     30 // VARIABLES //
     31 
     32 var LARGE_THRESHOLD = FLOAT64_BIGGEST * 0.5;
     33 var SMALL_THRESHOLD = FLOAT64_SMALLEST * ( 2.0 / EPS );
     34 var RECIP_EPS_SQR = 2.0 / ( EPS * EPS );
     35 
     36 
     37 // MAIN //
     38 
     39 /**
     40 * Computes the inverse of a complex number.
     41 *
     42 * @private
     43 * @param {(Array|TypedArray|Object)} out - output array
     44 * @param {number} re - real component
     45 * @param {number} im - imaginary component
     46 * @returns {(Array|TypedArray|Object)} output array
     47 *
     48 * @example
     49 * var out = new Array( 2 );
     50 *
     51 * var v = cinv( out, 2.0, 4.0 );
     52 * // returns [ 0.1, -0.2 ]
     53 *
     54 * var bool = ( v === out );
     55 * // returns true
     56 */
     57 function cinv( out, re, im ) {
     58 	var ab;
     59 	var s;
     60 	var r;
     61 	var t;
     62 
     63 	ab = max( abs(re), abs(im) );
     64 	s = 1.0;
     65 	if ( ab >= LARGE_THRESHOLD ) {
     66 		re *= 0.5;
     67 		im *= 0.5;
     68 		s *= 0.5;
     69 	} else if ( ab <= SMALL_THRESHOLD ) {
     70 		re *= RECIP_EPS_SQR;
     71 		im *= RECIP_EPS_SQR;
     72 		s *= RECIP_EPS_SQR;
     73 	}
     74 	if ( abs( im ) <= abs( re ) ) {
     75 		r = im / re;
     76 		t = 1.0 / ( re + (im*r) );
     77 		out[ 0 ] = t;
     78 		out[ 1 ] = -r * t;
     79 	} else {
     80 		r = re / im;
     81 		t = 1.0 / ( im + (re*r) );
     82 		out[ 0 ] = r * t;
     83 		out[ 1 ] = -t;
     84 	}
     85 	out[ 0 ] *= s;
     86 	out[ 1 ] *= s;
     87 	return out;
     88 }
     89 
     90 
     91 // EXPORTS //
     92 
     93 module.exports = cinv;