agentscape/numbers/RandomGenerator.js

Agentscape is a library for creating agent-based simulations. It provides a simple API for defining agents and their behavior, and for defining the environment in which the agents interact. Agentscape is designed to be flexible and extensible, allowing

import prand from 'pure-rand';
export default class RandomGenerator {
    constructor(seed) {
        this.seed = seed !== null && seed !== void 0 ? seed : Date.now() ^ (Math.random() * 0x100000000);
        this.generator = prand.xoroshiro128plus(seed);
    }
    jump() {
        this.generator = this.generator.jump();
    }
    /**
     * Returns a uniformly distributed random integer between min and max
     */
    uniformInt(min, max) {
        const [value, rng] = prand.uniformIntDistribution(min, max)(this.generator);
        this.generator = rng;
        return value;
    }
    /**
     * Returns an array of uniformly distributed random integers between min and max
     */
    uniformIntArray(min, max, size) {
        const result = [];
        for (let i = 0; i < size; i++) {
            result.push(this.uniformInt(min, max));
        }
        return result;
    }
    /*
    * Returns a uniformly distributed random float between min and max
    */
    uniformFloat(min, max) {
        const [value, rng] = prand.uniformIntDistribution(min * 1000, max * 1000)(this.generator);
        this.generator = rng;
        return value / 1000;
    }
    /**
     * Returns an array of uniformly distributed random floats between min and max.
     */
    uniformFloatArray(min, max, size) {
        const result = [];
        for (let i = 0; i < size; i++) {
            result.push(this.uniformFloat(min, max));
        }
        return result;
    }
    /**
     * Returns a normally distributed random number with mean mu and standard deviation sigma.
     */
    normalFloat(mu, sigma) {
        let u = 0, v = 0;
        while (u === 0)
            u = 1 - this.uniformFloat(0, 1);
        while (v === 0)
            v = this.uniformFloat(0, 1);
        return sigma * Math.sqrt(-2.0 * Math.log(u)) * Math.cos(2.0 * Math.PI * v) + mu;
    }
    /**
     * Returns an array of normally distributed random numbers with mean mu and standard deviation sigma.
     */
    normalFloatArray(mu, sigma, size) {
        const result = [];
        for (let i = 0; i < size; i++) {
            result.push(this.normalFloat(mu, sigma));
        }
        return result;
    }
    /**
     * Returns a Poisson distributed random number with mean lambda.
     */
    poissonInt(lambda) {
        const L = Math.exp(-lambda);
        let k = 0;
        let p = 1;
        do {
            k++;
            p *= this.uniformFloat(0, 1);
        } while (p > L);
        return k - 1;
    }
    /**
     * Returns an array of Poisson distributed random numbers with mean lambda.
     */
    poissonIntArray(lambda, size) {
        const result = [];
        for (let i = 0; i < size; i++) {
            result.push(this.poissonInt(lambda));
        }
        return result;
    }
    /**
     * Picks a single random element from the array.
     * Returns undefined if the array is empty.
     */
    pickRandom(array) {
        if (array.length === 0) {
            return undefined;
        }
        return array[this.uniformInt(0, array.length - 1)];
    }
    /**
     * Picks a random subset of the array without replacement.
     * Returns an empty array if the array is empty.
     */
    pickRandomArray(array, size) {
        if (array.length === 0) {
            return [];
        }
        const result = [];
        const copy = array.slice();
        for (let i = 0; i < size; i++) {
            const index = this.uniformInt(0, copy.length - 1);
            result.push(copy[index]);
            copy.splice(index, 1);
        }
        return result;
    }
    shuffle(array) {
        const result = array.slice();
        for (let i = result.length - 1; i > 0; i--) {
            const j = this.uniformInt(0, i);
            const temp = result[i];
            result[i] = result[j];
            result[j] = temp;
        }
        return result;
    }
}
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