Boids

Boids, developed by Craig Reynolds in 1986, is an artificial life program, simulating the flocking behaviour of birds. His paper on this topic was published in 1987 in the proceedings of the ACM SIGGRAPH conference. The name refers to a "bird-like object", but its pronunciation evokes that of "bird" in a stereotypical New York accent.

As with most artificial life simulations, Boids is an example of emergent behavior; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:
separation: steer to avoid crowding local flockmates
alignment: steer towards the average heading of local flockmates
cohesion: steer to move toward the average position of local flockmates

More complex rules can be added, such as obstacle avoidance and goal seeking.

The movement of Boids can be characterized as either chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.

The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals.

Boids work in a manner similar to cellular automata, since each boid "acts" autonomously and references a neighbourhood, as do cellular automata.

Real-time Transport Protocol

The Real-time Transport Protocol (RTP) defines a standardized packet format for delivering audio and video over the Internet. It was developed by the Audio-Video Transport Working Group of the IETF and first published in 1996 as RFC 1889, and superseded by RFC 3550 in 2003.

RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications and web-based push to talk features. For these it carries media streams controlled by H.323, MGCP, Megaco, SCCP, or Session Initiation Protocol (SIP) signaling protocols, making it one of the technical foundations of the Voice over IP industry.

RTP is usually used in conjunction with the RTP Control Protocol (RTCP). While RTP carries the media streams (e.g., audio and video) or out-of-band signaling (DTMF), RTCP is used to monitor transmission statistics and quality of service (QoS) information. When both protocols are used in conjunction, RTP is usually originated and received on even port numbers, whereas RTCP uses the next higher odd port number.

Electronic money

Electronic money (also known as e-money, electronic cash, electronic currency, digital money, digital cash or digital currency) refers to money or scrip which is exchanged only electronically. Typically, this involves use of computer networks, the internet and digital stored value systems. Electronic Funds Transfer (EFT) and direct deposit are examples of electronic money. Also, it is a collective term for financial cryptography and technologies enabling it.

While electronic money has been an interesting problem for cryptography (see for example the work of David Chaum and Markus Jakobsson), to date, use of digital cash has been relatively low-scale. One rare success has been Hong Kong's Octopus card system, which started as a transit payment system and has grown into a widely used electronic cash system. Singapore also has an electronic money implementation for its public transportation system (commuter trains, bus, etc), which is very similar to Hong Kong's Octopus card and based on the same type of card (FeliCa). There is also one implementation in the Netherlands, known as Chipknip.

Mathematical markup languages

A mathematical markup language is a computer notation for representing mathematical formulae, based on mathematical notation. Specialized markup languages are necessary because computers normally deal with linear text and more limited character sets (although increasing support for Unicode is obsoleting very simple uses). A formally standardized syntax also allows a computer to interpret otherwise ambiguous content, for rendering or even evaluating. For computer-interpretable syntaxes, the most popular are TeX/LaTeX and MathML.



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DecryptingContent-Scrambling System DeCSS

DeCSS is a computer program capable of decrypting content on a DVD-Video disc encrypted using the Content-Scrambling System (CSS).

Origins and history

DeCSS was devised by three people, two of whom remain anonymous. It was released on the Internet mailing list LiViD in October 1999. The one known author of the trio is Norwegian programmer Jon Lech Johansen, whose home was raided in 2000 by Norwegian police. Still a teenager at the time, he was put on trial in a Norwegian court for violating Norwegian Criminal Code section 145[1], and faced a possible jail sentence of two years and large fines, but was acquitted of all charges in early 2003. However, on March 5, 2003, a Norwegian appeals court ruled that Johansen would have to be retried. The court said that arguments filed by the prosecutor and additional evidence merited another trial. On December 22, 2003, the appeals court agreed with the acquittal, and on January 5, 2004, Norway's Økokrim (Economic Crime Unit) decided not to pursue the case further.

The program was first released on October 6, 1999 when Johansen posted an announcement of DeCSS 1.1b, a closed source Windows-only application for DVD ripping, on the livid-dev mailing list. The source code was leaked before the end of the month. The first release of DeCSS was preceded by a few weeks by a program called DoD DVD Speed Ripper from a group called Drink or Die, which didn't include source code and which apparently did not work with all DVDs. Drink or Die reportedly disassembled the object code of the Xing DVD player to obtain a player key. The group that wrote DeCSS, including Johansen, came to call themselves Masters of Reverse Engineering and may have obtained information from Drink or Die.

The CSS decryption source code used in DeCSS was mailed to Derek Fawcus before DeCSS was released. When the DeCSS source code was leaked, Fawcus noticed that DeCSS included his css-auth code in violation of the GNU GPL. When Johansen was made aware of this, he contacted Fawcus to solve the issue and was granted a license to use the code in DeCSS under non-GPL terms.

On January 22, 2004, the DVD CCA dropped the case against Jon Johansen BJ93GJCCMXAR

Simultaneous multithreading

Simultaneous multithreading, often abbreviated as SMT, is a technique for improving the overall efficiency of superscalar CPUs with hardware multithreading. SMT permits multiple independent threads of execution to better utilize the resources provided by modern processor architectures.

Multithreading is similar in concept to preemptive multitasking but is implemented at the thread level of execution in modern superscalar processors.

Simultaneous multithreading (SMT) is one of the two main implementations of multithreading, the other form being temporal multithreading. In temporal multithreading, only one thread of instructions can execute in any given pipeline stage at a time. In simultaneous multithreading, instructions from more than one thread can be executing in any given pipeline stage at a time. This is done without great changes to the basic processor architecture: the main additions needed are the ability to fetch instructions from multiple threads in a cycle, and a larger register file to hold data from multiple threads. The number of concurrent threads can be decided by the chip designers, but practical restrictions on chip complexity have limited the number to two for most SMT implementations.

Because the technique is really an efficiency solution and there is inevitable increased conflict on shared resources, measuring or agreeing on the effectiveness of the solution can be difficult. Some researchers have shown that the extra threads can be used to proactively seed a shared resource like a cache, to improve the performance of another single thread, and claim this shows that SMT is not just an efficiency solution. Others use SMT to provide redundant computation, for some level of error detection and recovery.

However, in most current cases, SMT is about hiding memory latency, efficiency and increased throughput of computations per amount of hardware used.

Quantum dot cellular automaton

Quantum Dot Cellular Automata (sometimes referred to simply as quantum cellular automata, or QCA) — Any device designed to represent data and perform computation, regardless of the physics principles it exploits and materials used to build it, must have two fundamental properties: distinguishability and conditional change of state, the latter implying the former. This means that such a device must have barriers that make it possible to distinguish between states, and that it must have the ability to control these barriers to perform conditional change of state. For example, in a digital electronic system, transistors play the role of such controllable energy barriers, making it extremely practical to perform computing with them.

Cellular automata

A cellular automaton (CA) is an abstract system consisting of a uniform (finite or infinite) grid of cells. Each one of these cells can only be in one of a finite number of states at a discrete time. The state of each cell in this grid is determined by the state of its adjacent cells, also called the cell's "neighborhood." The most popular example of a cellular automaton was presented by John Horton Conway in 1970, which he named "The Game of Life."