Start Here

The Harmony Online Textbook

A Comprehensive Introduction to Concurrent Programming
Download the PDF Version

Installing Harmony

A Quick Start Guide

Language Reference

Language features and syntax

Library Reference

Built in modules and libraries

What's New in Harmony?

Changelog & Patch Notes


Requires Python 3.6+

HarmonyLang for VSCode

  • Syntax Highlighting
  • Intelligent Code Completion
  • In-editor Visualizer
  • Automatic Compiler Installation


Try out Harmony

Dining Philosophers

Formulated in 1965 by Edsger Dijkstra as a student exam exercise, presented in terms of computers competing for access to tape drive peripherals.

Peterson's Algorithm

An algorithm for mutual exclusion that allows two or more processes to share a single-use resource without conflict, using only shared memory for communication.

Hoare Monitor

A synchronization construct that allows threads to have both mutual exclusion and the ability to wait (block) for a certain condition to become false.

Reader/Writer Problem

One of the most common problems in concurrency, we want to prevent more than one thread modifying the shared resource simultaneously and allow for two or more readers to access the shared resource at the same time.


It would make for quite a poor banking experience to allow dollars to simply go missing or be created from thin air, however that's exactly what might happen with poorly designed concurrent programs.

Split Binary Semaphores

A technique originally discovered, but not recommended by, Tony Hoare. It uses a set of binary semaphores the sum of which never exceeds 1


What is Harmony?

Concurrent programming is hard to get right. A deadlock might occur only once in a million executions, caused by the most esoteric of circumstances. Harmony makes finding those bugs easy.

  • Checks every possible interleaving of processes
  • Detects non-compilance with invariants
  • Provides the shortest path to a failing execution

Learning programming in Harmony should be straightforward to those familiar with Python or similar languages. In addition to our online documentation, we provide a textbook in PDF form with many programming examples including Peterson's Algorithm, reader/writer locks, and split binary semaphores.

Read more


Our Primary Contributors

Robbert van Renesse

Creator and Advisor to the Harmony Project

Anthony Yang

Compilers & Data Output

William Ma

Compilers & Visualization

Kevin Sun

Design & Documentation

Renyu Li

Graphical User Interface

Past Team Members

Shi Chong Zhao


Contact Us


433 Gates Hall, Ithaca, NY 14853


+1 (607) 255-1021