Volunteer computing is a type of distributed computing in which people donate their computers' unused resources to a research-oriented project, and sometimes in exchange for credit points. The fundamental idea behind it is that a modern desktop computer is sufficiently powerful to perform billions of operations a second, but for most users only between 10–15% of its capacity is used. Common tasks such as word processing or web browsing leave the computer mostly idle.
The practice of volunteer computing, which dates back to the mid-1990s, can potentially make substantial processing power available to researchers at minimal cost. Typically, a program running on a volunteer's computer periodically contacts a research application to request jobs and report results. A middleware system usually serves as an intermediary.
History
The first volunteer computing project was the Great Internet Mersenne Prime Search, which started in January 1996. It was followed in 1997 by distributed.net. In 1997 and 1998, several academic research projects developed Java-based systems for volunteer computing; examples include Bayanihan, Popcorn, Superweb, and Charlotte.
The term volunteer computing was coined by Luis F. G. Sarmenta, the developer of Bayanihan. It is also appealing for global efforts on social responsibility, or Corporate Social Responsibility as reported in a Harvard Business Review.
In 1999, the SETI@home and Folding@home projects were launched. These projects received considerable media coverage, and each one attracted several hundred thousand volunteers.
Between 1998 and 2002, several companies were formed with business models involving volunteer computing. Examples include Popular Power, Porivo, Entropia, and United Devices.
In 2002, the Berkeley Open Infrastructure for Network Computing (BOINC) project was founded at University of California, Berkeley Space Sciences Laboratory, funded by the National Science Foundation. BOINC provides a complete middleware system for volunteer computing, including a client, client GUI, application runtime system, server software, and software implementing a project web site. The first project based on BOINC was Predictor@home, based at the Scripps Research Institute, which began operation in 2004. Soon thereafter, SETI@home and climateprediction.net began using BOINC. A number of new BOINC-based projects were created over the next few years, including Rosetta@home, Einstein@home, and AQUA@home. In 2007, IBM World Community Grid switched from the United Devices platform to BOINC.
Middleware
The client software of the early volunteer computing projects consisted of a single program that combined the scientific computation and the distributed computing infrastructure. This monolithic architecture was inflexible. For example, it was difficult to deploy new application versions.
More recently, volunteer computing has moved to middleware systems that provide a distributed computing infrastructure independent from the scientific computation. Examples include: BOINC is the most widely used middleware system. It offers client software for Windows, macOS, Linux, Android, and other Unix variants. XtremWeb is used primarily as a research tool. It is developed by a group based at the University of Paris-South. Xgrid is developed by Apple. Its client and server components run only on macOS. Grid MP is a commercial middleware platform developed by United Devices and was used in volunteer computing projects including grid.org, World Community Grid, Cell Computing, and Hikari Grid.
Most of these systems have the same basic structure: a client program runs on the volunteer's computer. It periodically contacts project-operated servers over the Internet, requesting jobs and reporting the results of completed jobs. This "pull" model is necessary because many volunteer computers are behind firewalls that do not allow incoming connections. The system keeps track of each user's "credit", a numerical measure of how much work that user's computers have done for the project.
Volunteer computing systems must deal with several issues involving volunteered computers: their heterogeneity, their churn (the tendency of individual computers to join and leave the network over time), their sporadic availability, and the need to not interfere with their performance during regular use.