A stand alone nodejs app and software module for creating numerical experiments with robots trading in a single market.
The induced supply and demand is configurable, as are the types and speeds of trading robots populating the market.
This code can run either in a browser or on NodeJS and would normally be a "middle" portion of a code stack. Visualizations and friendly user-interfaces are the responsibility of other code, or you, the user.
Programmer's Documentation on ESDoc
The ESDoc site for single-market-robot-simulator contains documentation prepared from source code of this module.
installation not necessary -- use Docker
No installation is necessary if you have Docker (highly recommended for Windows and Mac usage). Skip to the "Usage" section.
To run as a nodejs command-line program, clone this repository and run
npm install -D or
npm i -D from the cloned directory to install all of the dependencies, including the testing and development dependencies
git clone https://github.com/DrPaulBrewer/single-market-robot-simulator cd ./single-market-robot-simulator npm install -D
If, instead, you want to use it as a library in another module to be released on npm, simply use
npm i -S as usual:
npm i single-robot-market-simulator -S
To use this as part of a web site, you will probably want to look at something like browserify, jspm, or webpack to server as a wrapper and help with bundling and integration.
To use this as a library on the browser with
jspm, you should set an override option on install forcing dependency
This was done in the robot-trading-webapp example prototype web app that uses a very early version of this code (1.0.0) from May, 2017. The "robot-trading-webapp" prototype is no longer under active development and does not receive updates or bug fixes. You may still try it but I do not recommend it for producing new research data.
It can also be used with
webpack. I do not recall if any
special settings are required.
Paid App Under Development
An afforable paid web app is in development that is much nicer, includes visualization and an editor, has time-saving features, and integrates with Google Cloud and Google Drive.
Configuration is a matter of preparing a
sim.json file BEFORE usage.
Configuration in the stand alone app occurs in a .json file called
config.json is currently read by
main() by default in stand-alone app mode but this may change to
sim.json in v6.0.0 to better agree with other contexts (, and the Docker stand-alones) where the file
sim.json is used,
When used as a software module, the configuration object
config read from the configuration file or other location is passed to the constructor
A partial (but still valid) machine and human readable format for
config.json is given in
configSchema.json as a JSON Schema.
A more human-readable version for most of the allowed fields can be found in the programmer's documentation for the public constructor config params for
Configurable supply and demand
The values and costs to be distributed among the trading robots are configured in the properties
sellerCosts, each an array that is distributed round-robin style to the buyer robots and seller robots respectively. Each of these values and costs will be distributed exactly once at the beginning of each period of the market.
To be clear, if the
numberOfBuyers exceeds the length of
buyerValues, then some buyers will not receive a unit value. Those buyers will exist but do nothing. If the length of
buyerValues exceeds the
numberOfBuyers then some buyers will receive more than one unit value, which is OK and even expected. By "round-robin" I mean that an element
buyerValues will be assigned to buyer
j mod numberOfBuyers . This form of specification is not convenient for every imaginable use, but it is convenient for setting a particular aggregate supply and demand and keeping it constant while tinkering with the number of buyers, sellers or other parameters.
The descending sorted
buyerValues can be used to form a step function that is the aggregate demand function for the market.
Similarly the ascending sorted
sellerCosts can be used to form a step function that is the aggregate supply function for the market.
Robot Trading agents
The types of buyers and sellers are set in configration properties
sellerAgentType and the buyers and sellers configured round-robin from these types.
For example, if there is only one type of buyer, then all buyers are that type. If there are two types of buyers configured then the buyers will alternate between these types, with half the buyers will be the first type, and half the buyers will be the second type if the number of buyers is even. If the number of buyers is odd then there will be an extra buyer of the first type. Perhaps a good practice is to have the buyerAgentType and sellerAgentType arrays have an entry for each buyer and seller, but for convenience in simple cases the round robin is used.
The module market-agents is imported to provide the robot trading agents.
The algorithms provided are intentionally fairly simple when compared to Neural Networks and some other approaches to machine learning. Several of the algorithms chosen have been the topics of papers in the economics literature.
Among the choices are:
- The Zero Intelligence trader of Gode and Sunder that bids/asks randomly for non-zero profit.
- a Sniper similar to Kaplan's Sniper algorithm but explicitly liquidity-reducing. For now, I still call it "KaplanSniperAgent" because of its historical roots. See .
- a "truthful" or identity-function algorithm that always bids the unit value or asks the unit cost.
- a bisection algorithm that bids or asks halfway between the current bid/current ask if profitable to do so, and initially bids/asks an extreme value when no bid/ask is present
- a "oneupmanship" algorithm that increases the bid or decreases the ask by 1 unit if profitable to do so
- others, and a base class for writing your own algorithm
Stand Alone App
when run from Docker
It is possible to run the software on Docker without having a Linux system (otherwise recommended), and without installing nodejs and npm (otherwise required). Docker downloads a Linux container containing everything needed and runs it on any computer.
Create a work directory containing a
sim.json file with the simulation configuration. This follows the format given above
config.json only the filename is changed.
The most recent Docker container is for version 5.6.0. To run that, use this docker command:
docker run -it \ -v /path/to/your/work/directory:/work \ drpaulbrewer/single-market-robot-simulator:5.6.0
To run the simulator code as it existed for the research project  (version 4.3.0), use this Docker command:
docker run -it \ -v /path/to/your/work/directory:/work \ drpaulbrewer/single-market-robot-simulator:4.3.0
when installed from GitHub
If installed from github onto a suitable system (preferably Linux, though it may run on Windows 10 or Mac -- and with nodejs and npm previously installed) it can be used as a stand alone nodejs app.
node build/index.js from the installation directory will run the simulation, reading the
config.json file and outputting various log files.
You can name a file like
/my-files/research/project123/sim.json but the simulator will then fetch that file but continue to run and output market data files into the current directory, and not necessarily in the directory where that
sim.json file is located. Instead, consider copying the
sim.json file to a new directory,
cd to that new directory, and run
node /path/to/single-market-robot-simulator/build/index.js sim.json
where you should replace
/path/to/ with the actual directory path where the simulator is installed.
A number of .csv comma-separated-value files are produced containing the market data.
Output files include:
These logs have header rows and are compatible with Excel and other spreadsheets and most analysis software.
There are no output progress messages unless
quiet: false is in the
sim.json properties. There is a file called
period that can be used as a progress indicator. It contains only a single number -- the current period number.
Usage as a software module
Depending on whether you are using ES6 or CJS modules, importing looks like this:
import * as SMRS from 'single-market-robot-simulator'; // ES6 const SMRS = require("single-market-robot-simulator"); // CJS
and returns an object
Simulation and a few other miscellaneous items. Ideally, this code
On the browser, standard browser security policies require different procedures for writing out files. Therefore, the data logs cannot be immediately written out to .csv files (as with the stand alone app) but are maintained in memory for use with other systems, such as browser-based plotting software. It is the responsibility of other software (e.g.
single-market-robot-simulator-savezip) to write the logs to browser-side
.csv files or elsewhere and/or to provide for visualizations.
Simulations can be run in either synchronous or asynchronous mode. Asynchronous mode is useful for running on the browser so that the event loop and user interface do not freeze while waiting for simulation results.
Example source code for a web-based simulator based on
single-market-robot-simulator may be found at
and the resulting simulator web app is at
However, those are very early prototypes (v1, May 2017), are not actively updated, and should not be relied upon for new research. I have a paid version of this market simulator in development. You should also prefer the docker and stand-alone versions to the early web prototype.
from the local git-cloned and npm-installed copy of this repository will run the tests.
You may also be interested in the tests for
market-example-contingent or other dependencies, which are available from those modules' directories.
You can also click on the build or coverage badges to view public test reports.
Copyright 2016- Paul Brewer, Economic and Financial Technology Consulting LLC
The software is available under the industry standard open souce MIT License.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 Allocative Efficiency of Markets with Zero-Intelligence Traders: Market as a Partial Substitute for Individual Rationality Dhananjay K. Gode and Shyam Sunder, Journal of Political Economy, Vol. 101, No. 1 (Feb., 1993), pp. 119-137
 This sniper robot was used for an academic research project and its history detailed in Appendix 1 of the resulting publication:
Paul Brewer and Anmol Ratan (2019), "Profitability, Efficiency, and Inequality in Double Auction Markets with Snipers." Accepted at Journal of Economic Behavior and Organization, forthcoming.
Before asking the author for help
I hope you enjoy the free software
and the thrill of researching and solving problems
I will appreciate a social "hello" from researchers, students, and others attempting to use the free version of this software.
But I also reserve the right to ignore email. Don't take it personally, or as a snub. 24-hr on call unlimited free support is not included with this free software, or any free software for that matter
I have written this section to help with that issue.
First, if you are a student, I wouldn't dream of taking your homework problem or class project problem away from you -- even if, in a moment of weakness or desperation the day before the deadline you were having trouble completing it at the last minute. You can do it! I believe in you! And, it is a learning experience.
Technology can be frustrating, and having a conversation about frustration that also involves lacking useful notes and being ill-prepared, is often mutually frustrating and tends to be a waste of time. If that seems arrogant, imagine I am talking about myself.
I lack useful notes on what happens if the software is run on unsuitable machines. Or what happens when problems of unclear documentation or insufficient prior experience combine with other issues between the keyboard and the chair.
And I am ill-prepared to continue working for free on things I actually care about, and much less enthusiastic about becoming someone's private arbitrage gain. If this simulation software helps with your group's goals and is saving money by providing a head-start on research or teaching projects -- please consider becoming a financial sponsor.
I wrote above that I might lack notes or be ill-prepared.
Keep in mind that you might also lack useful notes or be ill-prepared (i.e. it doesn't work but you don't know why and you didn't write anything down about the error messages or exactly what you did; or your question is about how to construct a simulation without reading the documentation or studying any examples).
Before asking me a question, please try these things first:
- consider that your problem might be solved faster by
- asking a local computer-savvy colleague to sit down with you and review what is happening.
- explaining the question out loud to an unfamiliar (or even a fictional) person can help you solve your own problem. Also known as Rubber duck debugging.
- upgrading your computer or using a better or different computer. More cores, 8 GB or more ram, and an SSD are all a plus. The simulator software is single-threaded. But Docker on Windows or Mac installs its own Linux -- so on Docker you'll benefit from at least 2 cores. Typically a full-sized desktop has more heat dissipation and can be higher performance than a laptop or mini cube.
- optionally spending less than $50 on the paid version of this software when available at https://econ1.net -- which will be used over the web (no installation), be compatible with the free Docker usage method above, has a web-based editor, can run in the cloud, and stores the results in your Google Drive.
- be sure you really have a short, solvable question
- open-ended discussions are not short, solvable
- not short if it takes several pages to ask or answer
- constructive criticism is ok but I'll be the judge of its constructive-ness. Keep it civil and remember that you haven't paid anything for this software, it was not a custom project for you, and my goals may have nothing to do with your specific needs.
- be prepared to answer: "What have you tried?"
- if suspecting a bug, prepare and test a short, complete, verifiable list of steps to reproduce it and include that with your question
- don't be be a help vampire. While it seems natural to ask preliminary questions instead of "wasting time" reading, learning, or trying things yourself -- the strategy of pushing your preparatory work (reading, learning, trying things yourself) off on others is generally seen as counterproductive.
- others can often answer your general computer or programming question faster and better than I can. Post a public question to a popular, relevant forum. The sites below are popular and include peer-review of questions and answers. The same rules apply -- do your homework before asking: