GApop is a genetic algorithm external for Pd and MAX/MSP, written in C .
Pure Data (or Pd) is a graphical programming language developed by Miller Puckette in the 1990s for the creation of interactive computer music and multimedia works. Though Puckette is the primary author of the software, Pd is an open source project and has a large developer base working on new extensions to the program. It is released under a license similar to the BSD license.
Pd is very similar in scope and design to Puckette's original Max program (developed while he was at IRCAM), and is to some degree interoperable with Max/MSP, the commercial successor to the Max language. Both Pd and Max are arguably examples of Dataflow programming languages. In such languages, functions or "objects" are linked or "patched" together in a graphical environment which models the flow of the control and audio. Unlike the original version of Max, however, Pd was always designed to do control-rate and audio processing on the host CPU, rather than offloading the synthesis and signal processing to a DSP board (such as the Ariel ISPW which was used for Max/FTS). Pd code forms the basis of David Zicarelli's MSP extensions to the Max language to do software audio processing.
Like Max, Pd has a modular code base of externals or objects which are used as building blocks for programs written in the software. This makes the program arbitrarily extensible through a public API, and encourages developers to add their own control and audio routines, either in the C programming language or, with the help of other externals, in Python, Ruby, Scheme and many other languages as well. However, Pd is a programming language in its own right. Modular, reusable units of code written natively in Pd, called "patches" or "abstractions", are used as standalone programs and freely shared among the Pd user community, and no other programming skill is required to use Pd effectively.
With the addition of the Graphics Environment for Multimedia (GEM) external, and externals designed to work with it (like Pure Data Packet / PiDiP for Linux, framestein for Windows, GridFlow for n-dimensional matrix processing that integrates pure data with the Ruby programming language, etc.), it is possible to create and manipulate video, OpenGL graphics, images, etc. in realtime with seemingly endless possiblilities for interactivity with audio, external sensors, etc.
Additionally, Pd is natively designed to enable live collaboration across networks or the internet, allowing musicians connected via LAN or even in disparate parts of the globe to create music together in real time.