Your first model

Open the simulator#

Go to starter.mysolvers.com. There is no sign-up and nothing to install. You land on an empty canvas with a toolbar down the left edge — across the top on a phone — and playback controls at the bottom. Scroll, or pinch on a touch screen, to zoom.

Build the model#

1. Open the Queueing Systems button in the toolbar. It unfolds into the four components you can place: Generator, Queue, Delay and Server.
2. Pick Generator and click on the canvas to drop it. Do the same for a Queue to its right and a Server to the right of that. Each gets a numbered name — Server 1, Server 2 — so several of a kind stay apart.
3. Drag from the connection handle on the right-hand side of the generator and drop anywhere on the queue, then do the same from the queue to the server. Entities will travel along those arrows.
4. Switch back to the Selection tool and click a component. A small toolbar appears above it with that component's settings, plus buttons to rename, copy or delete it; double-clicking the name renames it too. Select several components and you can copy or delete them together — a copy keeps the connections between them.

If something is left unconnected the simulator will not start: it highlights the offending component and explains what is missing. The wiring rules are short — a generator needs somewhere to send entities, a queue, a server and a delay each need a source, and a server can only pull from a queue.

Run it#

Press play at the bottom of the screen. The clock in the top right corner starts counting simulated time, and entities begin moving through the model.

Dots travel along every connection as entities cross it — green for those delivered, red for those a full queue refused — so you can see where the traffic goes and where it is lost without opening a single chart.

Each component shows a row of chart toggles above it. Turn on the queue's length chart and the server's state chart first — between them they tell you almost everything about a simple model. Next to the clock, the whole model's figures are always on show: entities completed and dropped, the share lost, and the mean, median, 95th percentile and maximum of the cycle time — how long entities took to travel through the system end to end.

Every live figure and chart is read over a sliding window of simulated time. The Chart window control in the top left corner sets it to the last 10 seconds, 30 seconds or minute: a short window reacts quickly to a change, a long one smooths out the noise.

The speed control next to play runs the simulation from a quarter of real time up to sixteen times faster, so a long-running effect does not need a long wait. Restart replays the model from an empty state; stop returns you to editing.

Tune it while it runs#

Settings can be changed without stopping the simulation, which is the fastest way to build intuition for a system. With the model running, select the generator and raise its arrival rate above the server's service rate. Within seconds the queue fills, the server stops idling, red dots appear in front of the queue, and the generator starts recording dropped entities.

Then raise the queue's capacity and watch what changes — and what does not. A bigger buffer absorbs bursts and cuts the drops, but it cannot make a server faster than it is: the cycle time simply climbs. That trade-off between waiting and losing work is the heart of capacity planning, and it is visible here in a couple of clicks.

Save your work#

Your model is stored in the browser as you edit it and restored the next time you open the simulator, so closing the tab is safe. The browser keeps one model at a time, so opening or changing a library model replaces the one you had. To keep a copy, or to move a model to another machine, use Save to file in the toolbar and Open file to bring it back. Models saved by an older version of the simulator still load, with a warning that they predate the current format.

Where to go next#

A live run shows how a model behaves; it does not tell you how sure you can be of a number. For that, press Batch run beside play: the model runs many times at full speed and every result comes back with a confidence interval. The batch runs page walks through it.

If you would rather start from something ready-made, the Model Library button in the toolbar opens the classic queues — M/M/1, M/M/c and M/M/1/K — prepared and ready to run. They are also listed in the model library.