40 lines
1.0 KiB
JavaScript
40 lines
1.0 KiB
JavaScript
export default class Random {
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// Xorshift+ 64-bit random generator https://en.wikipedia.org/wiki/Xorshift
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constructor() {
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this.s = new Uint32Array(4);
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}
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reset() {
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// Arbitrary random seed with roughly balanced 1s / 0s
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// (taken from running Math.random a few times)
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this.s[0] = 0x177E9C74;
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this.s[1] = 0xAE6FFDCE;
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this.s[2] = 0x3CF4F32B;
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this.s[3] = 0x46449F88;
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}
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nextFloat() {
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/* eslint-disable no-bitwise */ // Bit-ops are part of the algorithm
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/* eslint-disable prefer-destructuring */ // Clearer this way
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const range = 0x100000000;
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let x0 = this.s[0];
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let x1 = this.s[1];
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const y0 = this.s[2];
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const y1 = this.s[3];
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this.s[0] = y0;
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this.s[1] = y1;
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x0 ^= (x0 << 23) | (x1 >>> 9);
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x1 ^= (x1 << 23);
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this.s[2] = x0 ^ y0 ^ (x0 >>> 17) ^ (y0 >>> 26);
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this.s[3] = (
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x1 ^ y1 ^
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((x0 << 15) | (x1 >>> 17)) ^
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((y0 << 6) | (y1 >>> 26))
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);
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return (((this.s[3] + y1) >>> 0) % range) / range;
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/* eslint-enable no-bitwise */
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/* eslint-enable prefer-destructuring */
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}
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}
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