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🔗 Video games 🔗 Computer science 🔗 Mathematics

Fast inverse square root, sometimes referred to as Fast InvSqrt() or by the hexadecimal constant 0x5F3759DF, is an algorithm that estimates ​¹⁄_√x, the reciprocal (or multiplicative inverse) of the square root of a 32-bit floating-point number x in IEEE 754 floating-point format. This operation is used in digital signal processing to normalize a vector, i.e., scale it to length 1. For example, computer graphics programs use inverse square roots to compute angles of incidence and reflection for lighting and shading. The algorithm is best known for its implementation in 1999 in the source code of Quake III Arena, a first-person shooter video game that made heavy use of 3D graphics. The algorithm only started appearing on public forums such as Usenet in 2002 or 2003. At the time, it was generally computationally expensive to compute the reciprocal of a floating-point number, especially on a large scale; the fast inverse square root bypassed this step.

The algorithm accepts a 32-bit floating-point number as the input and stores a halved value for later use. Then, treating the bits representing the floating-point number as a 32-bit integer, a logical shift right by one bit is performed and the result subtracted from the number 0x5F3759DF, which is a floating point representation of an approximation of √2¹²⁷. This results in the first approximation of the inverse square root of the input. Treating the bits again as a floating-point number, it runs one iteration of Newton's method, yielding a more precise approximation.

The algorithm was originally attributed to John Carmack, but an investigation showed that the code had deeper roots in both the hardware and software side of computer graphics. Adjustments and alterations passed through both Silicon Graphics and 3dfx Interactive, with Gary Tarolli's implementation for the SGI Indigo as the earliest known use. It is not known how the constant was originally derived, though investigation has shed some light on possible methods.

With subsequent hardware advancements, especially the x86 SSE instruction rsqrtss, this method is not generally applicable to modern computing, though it remains an interesting example both historically and for more limited machines.

🔗 Biography 🔗 Disambiguation

William Adams may refer to:

🔗 Physics

The Einstein–Szilard or Einstein refrigerator is an absorption refrigerator which has no moving parts, operates at constant pressure, and requires only a heat source to operate. It was jointly invented in 1926 by Albert Einstein and his former student Leó Szilárd, who patented it in the U.S. on November 11, 1930 (U.S. Patent 1,781,541). The three working fluids in this design are water, ammonia and butane. The Einstein refrigerator is a development of the original three-fluid patent by the Swedish inventors Baltzar von Platen and Carl Munters.

🔗 Guild of Copy Editors 🔗 Automobiles

The Chrysler Turbine Car is an experimental two-door hardtop coupe powered by a turbine engine and manufactured by Chrysler from 1963–1964. The bodywork was constructed by Italian design studio Carrozzeria Ghia and Chrysler completed the final assembly in Detroit. A total of 55 cars were manufactured: five prototypes and a limited run of 50 cars for a public user program. All have a signature metallic paint named "turbine bronze", roughly the color of root beer. The car was styled by Elwood Engel and the Chrysler studios and featured power brakes, power steering, and a TorqueFlite transmission.

The Chrysler turbine engine program that produced the Turbine Car began during the late 1930s and created prototypes that completed long-distance trips in the 1950s and early 1960s. The A-831 engines that powered the Ghia-designed Turbine Car could operate on many fuels, required less maintenance, and lasted longer than conventional piston engines, although they were much more expensive to produce.

After testing, Chrysler conducted a user program from October 1963 to January 1966 that involved 203 drivers in 133 cities in the United States cumulatively driving more than one million miles (1.6 million km). The program helped the company determine problems with the cars, notably with their complicated starting procedure, relatively unimpressive acceleration, and sub-par fuel economy and noise. The experience also revealed advantages of the turbine engines, including their remarkable durability, smooth operation, and relatively modest maintenance requirements.

After the user program ended in 1966, Chrysler reclaimed the cars and destroyed all but nine; Chrysler kept two cars, six are displayed at museums in the United States, and one is in a private collection. Chrysler's turbine engine program ended in 1979, largely due to the failure of the engines to meet government emissions regulations, relatively poor fuel economy, and as a condition of receiving a government loan in 1979.

🔗 Technology 🔗 Medicine 🔗 Psychology 🔗 Medicine/Psychiatry 🔗 Artificial Intelligence

Chatbot psychosis, also called AI psychosis, is a phenomenon wherein individuals reportedly develop or experience worsening psychosis, such as paranoia and delusions, in connection with their use of chatbots. The term was first suggested in a 2023 editorial by Danish psychiatrist Søren Dinesen Østergaard. It is not a recognized clinical diagnosis.

Journalistic accounts describe individuals who have developed strong beliefs that chatbots are sentient, are channeling spirits, or are revealing conspiracies, sometimes leading to personal crises or criminal acts. Proposed causes include the tendency of chatbots to provide inaccurate information ("hallucinate") and to affirm or validate users' beliefs, or their ability to mimic an intimacy that users do not experience with other humans.

🔗 Biology 🔗 Cognitive science 🔗 Neuroscience

The free energy principle tries to explain how (biological) systems maintain their order (non-equilibrium steady-state) by restricting themselves to a limited number of states. It says that biological systems minimise a free energy function of their internal states, which entail beliefs about hidden states in their environment. The implicit minimisation of variational free energy is formally related to variational Bayesian methods and was originally introduced by Karl Friston as an explanation for embodied perception in neuroscience, where it is also known as active inference.

The free energy principle is that systems—those that are defined by their enclosure in a Markov blanket—try to minimize the difference between their model of the world and their sense and associated perception. This difference can be described as "surprise" and is minimized by continuous correction of the world model of the system. As such, the principle is based on the Bayesian idea of the brain as an “inference engine”. Friston added a second route to minimization: action. By actively changing the world into the expected state, systems can also minimize the free energy of the system. Friston assumes this to be the principle of all biological reaction.. Friston also believes his principle applies to mental disorders as well as to artificial intelligence. AI implementations based on the active inference principle have shown advantages over other methods.

The free energy principle has been criticized for being very difficult to understand, even for experts. Discussions of the principle have also been criticized as invoking metaphysical assumptions far removed from a testable scientific prediction, making the principle unfalsifiable. In a 2018 interview, Friston acknowledged that the free energy principle is not properly falsifiable: "the free energy principle is what it is — a principle. Like Hamilton’s Principle of Stationary Action, it cannot be falsified. It cannot be disproven. In fact, there’s not much you can do with it, unless you ask whether measurable systems conform to the principle."

🔗 United States 🔗 Biography 🔗 Computer science 🔗 Biography/science and academia 🔗 United States/Indiana

John Charles Reynolds (June 1, 1935 – April 28, 2013) was an American computer scientist.

🔗 Philosophy 🔗 Skepticism 🔗 Psychology 🔗 Philosophy/Contemporary philosophy 🔗 Philosophy/Philosophy of mind 🔗 Alternative Views 🔗 Neuroscience

Bicameralism (the condition of being divided into "two-chambers") is a hypothesis in psychology that argues that the human mind once operated in a state in which cognitive functions were divided between one part of the brain which appears to be "speaking", and a second part which listens and obeys—a bicameral mind. The term was coined by Julian Jaynes, who presented the idea in his 1976 book The Origin of Consciousness in the Breakdown of the Bicameral Mind, wherein he made the case that a bicameral mentality was the normal and ubiquitous state of the human mind as recently as 3,000 years ago, near the end of the Mediterranean bronze age.

🔗 Books

The Opium of the Intellectuals (French: L'Opium des intellectuels) is a book written by Raymond Aron and published in 1955. It was first published in an English translation in 1957.

🔗 Video games

MIDI Maze is a networked first-person shooter for the Atari ST developed by Xanth Software F/X and released in 1987 by Hybrid Arts. The game takes place in a maze of untextured walls. The world animates smoothly as the player turns, much like the earlier Wayout, instead of only permitting 90 degree changes of direction. It has been suggested that MIDI Maze, using the built-in MIDI ports of the Atari ST for networking, introduced the concept of deathmatch combat. The game found a wider audience on the Game Boy as Faceball 2000.

The original MIDI Maze team consisted of James Yee as the business manager, Michael Park as the graphic and networking programmer, and George Miller writing the AI and drone logic.