sqrt.js (1752B)
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 // VARIABLES // 22 23 // Set the second most significant bit: 00100000000000000000000000000000 => 1<<30 = 1073741824 24 var BIT = 1073741824 >>> 0; // asm type annotation 25 26 27 // MAIN // 28 29 /** 30 * Returns an integer square root. 31 * 32 * @param {uinteger32} x - input value 33 * @returns {uinteger32} integer square root 34 * 35 * @example 36 * var v = sqrt( 9 >>> 0 ); 37 * // returns 3 38 * 39 * @example 40 * var v = sqrt( 2 >>> 0 ); 41 * // returns 1 42 * 43 * @example 44 * var v = sqrt( 3 >>> 0 ); 45 * // returns 1 46 * 47 * @example 48 * var v = sqrt( 0 >>> 0 ); 49 * // returns 0 50 */ 51 function sqrt( x ) { 52 var root; 53 var bit; 54 var sum; 55 var y; 56 57 y = x >>> 0; // asm type annotation 58 59 root = 0 >>> 0; // asm type annotation 60 bit = BIT; 61 62 // `bit` should start as the highest power of `4` less than or equal to `x`: 63 while ( bit > y ) { 64 bit >>>= 2; 65 } 66 // Perform a digit-by-digit/abacus computation... 67 while ( bit !== 0 ) { 68 sum = ( root + bit ) >>> 0; // asm type annotation 69 root >>>= 1; 70 if ( x >= sum ) { 71 x -= sum; 72 root += bit; 73 } 74 bit >>>= 2; 75 } 76 // Note: `x` is the remainder 77 78 return root >>> 0; // asm type annotation 79 } 80 81 82 // EXPORTS // 83 84 module.exports = sqrt;