mirror of
https://github.com/pezkuwichain/pezkuwi-common.git
synced 2026-04-22 06:47:57 +00:00
33 lines
1.2 KiB
JavaScript
33 lines
1.2 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.nSqrt = nSqrt;
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const x_bigint_1 = require("@pezkuwi/x-bigint");
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const consts_js_1 = require("./consts.js");
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const toBigInt_js_1 = require("./toBigInt.js");
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/**
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* @name nSqrt
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* @summary Calculates the integer square root of a bigint
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*/
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function nSqrt(value) {
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const n = (0, toBigInt_js_1.nToBigInt)(value);
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if (n < consts_js_1._0n) {
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throw new Error('square root of negative numbers is not supported');
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}
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// https://stackoverflow.com/questions/53683995/javascript-big-integer-square-root/
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// shortcut <= 2^53 - 1 to use the JS utils
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if (n <= consts_js_1._2pow53n) {
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// ~~ is more performant that Math.floor
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return (0, x_bigint_1.BigInt)(~~Math.sqrt(Number(n)));
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}
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// Use sqrt(MAX_SAFE_INTEGER) as starting point. since we already know the
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// output will be larger than this, we expect this to be a safe start
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let x0 = consts_js_1._sqrt2pow53n;
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while (true) {
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const x1 = ((n / x0) + x0) >> consts_js_1._1n;
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if (x0 === x1 || (x0 === (x1 - consts_js_1._1n))) {
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return x0;
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}
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x0 = x1;
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}
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}
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