SimScript

A Discrete Event Simulation Library in TypeScript.

SimScript uses JavaScript's async/await features to make simulations easy to write and understand.

SimScript simulations are built using these classes:

Simulation

Simulations create resources (queues) and entities which execute an async script method that describes the actions each entity should perform.

Queues

Queues represent resources that can be seized and released by entities. Queues keep track of their utilization and may constrain the flow of entities through the simulation.

Entities

Entities represent active elements that execute scripts. Scripts are async methods that contain instructions for entities. Typical actions include entering and leaving queues, going through delays, and sending or waiting for signals.

Animations

Animations use HTML or SVG elements to render entities waiting in queues or in transit between queues.

Animations are useful for presentations and also for debugging simulations.

Styles

SimScript includes a CSS file with some simple formatting for the tables and histograms you can create with the Simulation.getStatsTable and Tally.getHistogram methods.

To include that CSS in your projects, add this line to the main ts file in your project:

import "simscript/dist/simscript.css";

Example

This is the classic Barbershop simulation written in SimScript:

// https://try-mts.com/gpss-introduction-and-barber-shop-simulation/
export class BarberShop extends Simulation {
    qJoe = new Queue('Joe', 1);
    qWait = new Queue('Wait Area');

    // generate entities with inter-arrival times of 18 min for 8 hours * 7 days
    onStarting() {
        super.onStarting();
        this.timeEnd = 60 * 8 * 7; // simulation times are in minutes
        this.generateEntities(Customer, new Uniform(18 - 6, 18 + 6));
    }
}
class Customer extends Entity {
    service = new Uniform(15 - 3, 15 + 3);
    async script() {
        const shop = this.simulation as BarberShop;
        await this.enterQueue(shop.qWait); // enter the line
        await this.enterQueue(shop.qJoe); // seize Joe the barber
        this.leaveQueue(shop.qWait); // leave the line
        await this.delay(this.service.sample()); // get a haircut
        this.leaveQueue(shop.qJoe); // free Joe        
    }
}

Samples

The links below show some samples of SimScript simulations:

• Barbershop Classic GPSS simulation example: customers arrive at a barbershop, wait until the barber is available, get serviced, and leave.

• M/M/C Classic M/M/C queueing system. Entities arrive, are served by one of C servers, and leave.

• RandomVar Demonstrates some of the random variables implemented in SimScript.

• Crosswalk Uses the waitSignal and sendSignal methods to simulate a crosswalk.

• Animated Crosswalk Uses the Animation class to show an animated version of the Crosswalk simulation.