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🔗 Computing 🔗 Computer science

In computational complexity and optimization the no free lunch theorem is a result that states that for certain types of mathematical problems, the computational cost of finding a solution, averaged over all problems in the class, is the same for any solution method. The name alludes to the saying "no such thing as a free lunch", that is, no method offers a "short cut". This is under the assumption that the search space is a probability density function. It does not apply to the case where the search space has underlying structure (e.g., is a differentiable function) that can be exploited more efficiently (e.g., Newton's method in optimization) than random search or even has closed-form solutions (e.g., the extrema of a quadratic polynomial) that can be determined without search at all. For such probabilistic assumptions, the outputs of all procedures solving a particular type of problem are statistically identical. A colourful way of describing such a circumstance, introduced by David Wolpert and William G. Macready in connection with the problems of search and optimization, is to say that there is no free lunch. Wolpert had previously derived no free lunch theorems for machine learning (statistical inference). Before Wolpert's article was published, Cullen Schaffer independently proved a restricted version of one of Wolpert's theorems and used it to critique the current state of machine learning research on the problem of induction.

In the "no free lunch" metaphor, each "restaurant" (problem-solving procedure) has a "menu" associating each "lunch plate" (problem) with a "price" (the performance of the procedure in solving the problem). The menus of restaurants are identical except in one regard – the prices are shuffled from one restaurant to the next. For an omnivore who is as likely to order each plate as any other, the average cost of lunch does not depend on the choice of restaurant. But a vegan who goes to lunch regularly with a carnivore who seeks economy might pay a high average cost for lunch. To methodically reduce the average cost, one must use advance knowledge of a) what one will order and b) what the order will cost at various restaurants. That is, improvement of performance in problem-solving hinges on using prior information to match procedures to problems.

In formal terms, there is no free lunch when the probability distribution on problem instances is such that all problem solvers have identically distributed results. In the case of search, a problem instance in this context is a particular objective function, and a result is a sequence of values obtained in evaluation of candidate solutions in the domain of the function. For typical interpretations of results, search is an optimization process. There is no free lunch in search if and only if the distribution on objective functions is invariant under permutation of the space of candidate solutions. This condition does not hold precisely in practice, but an "(almost) no free lunch" theorem suggests that it holds approximately.

🔗 Metalworking 🔗 Measurement

A thousandth of an inch is a derived unit of length in a system of units using inches. Equal to 1⁄1000 of an inch, a thousandth is commonly called a thou (used for both singular and plural) or particularly in North America a mil (plural mils).

The words are shortened forms of the English and Latin words for "thousand" (mille in Latin). In international engineering contexts, confusion can arise because mil is a formal unit name in North America but mil or mill is also a common colloquial clipped form of millimetre. The units are considerably different: a millimetre is approximately 39 mils.

🔗 Companies 🔗 History 🔗 Architecture 🔗 Buddhism 🔗 Japan 🔗 Japan/History 🔗 Japan/Business and economy

Kongō Gumi Co., Ltd. (株式会社金剛組, Kabushiki Gaisha Kongō Gumi) is a Japanese construction company which was the world's oldest continuously ongoing independent company, operating for over 1,400 years. In January 2006, it became a subsidiary of Takamatsu.

🔗 Mathematics

The gömböc (Hungarian: [ˈɡømbøt͡s]) is a convex three-dimensional homogeneous body that when resting on a flat surface has just one stable and one unstable point of equilibrium. Its existence was conjectured by the Russian mathematician Vladimir Arnold in 1995 and proven in 2006 by the Hungarian scientists Gábor Domokos and Péter Várkonyi. The gömböc shape is not unique; it has countless varieties, most of which are very close to a sphere and all with a very strict shape tolerance (about 0.1 mm per 100 mm).

The most famous solution, capitalized as Gömböc to distinguish it from the generic gömböc, has a sharpened top, as shown in the photo. Its shape helped to explain the body structure of some tortoises in relation to their ability to return to equilibrium position after being placed upside down. Copies of the gömböc have been donated to institutions and museums, and the largest one was presented at the World Expo 2010 in Shanghai in China. In December 2017, a 4.5 m gömböc statue was installed in the Corvin Quarter in Budapest.

🔗 Fungi 🔗 Physiology

Radiotrophic fungi are fungi which appear to perform radiosynthesis, that is, to use the pigment melanin to convert gamma radiation into chemical energy for growth. This proposed mechanism may be similar to anabolic pathways for the synthesis of reduced organic carbon (e.g., carbohydrates) in phototrophic organisms, which convert photons from visible light with pigments such as chlorophyll whose energy is then used in photolysis of water to generate usable chemical energy (as ATP) in photophosphorylation or photosynthesis. However, whether melanin-containing fungi employ a similar multi-step pathway as photosynthesis, or some chemosynthesis pathways, is unknown.

🔗 Military history 🔗 Military history/African military history 🔗 Ethiopia 🔗 Military history/British military history

The British Expedition to Abyssinia was a rescue mission and punitive expedition carried out in 1868 by the armed forces of the British Empire against the Ethiopian Empire. Emperor Tewodros II of Ethiopia, then often referred to by the anglicized name Theodore, imprisoned several missionaries and two representatives of the British government in an attempt to get the attention of the British government, which had decided against his requests for military assistance. The punitive expedition launched by the British in response required the transportation of a sizable military force hundreds of miles across mountainous terrain lacking any road system. The formidable obstacles to the action were overcome by the commander of the expedition, General Sir Robert Napier, who was victorious in every battle with the troops of Tewodros, captured the Ethiopian capital and rescued all the hostages. The expedition was widely hailed on its return for achieving all its objectives.

Harold G. Marcus described the action as "one of the most expensive affairs of honour in history."

🔗 Time 🔗 Geology

Before Present (BP) years is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred in the past. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale, reflecting the origin of practical radiocarbon dating in the 1950s. The abbreviation "BP" has been interpreted retrospectively as "Before Physics"; that refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, making dating after that time likely to be unreliable.

In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP is explicitly Radio Carbon Years Before Present.

🔗 Trains

In rail transportation, a rolling highway or rolling road is a form of combined transport involving the conveying of road trucks by rail, referred to as Ro-La trains. The concept is a form of piggyback transportation.

The technical challenges to implement rolling highways vary from region to region. In North America, the loading gauge is often high enough to accommodate double stack containers, so the height of a semi-trailer on a flatcar is no issue. However, in Europe, except for purpose built lines such as the Channel Tunnel or the Gotthard Base Tunnel, the loading gauge height is much smaller, and it is necessary to transport the trailers with the tires about 30 cm (11.81 in) above the rails, so the trailers cannot be simply parked on the surface of a flat car above the wagon wheels or bogies. Making the wagon wheels smaller limits the maximum speed, so many designs allow the trailer to be transported with its wheels lower than the rail wagon wheels. An early approach in France was the Kangourou wagon with modified trailers. This technology did not survive, due to the market resistance to modified trailers. Today, three designs for these special wagons are in commercial service, "Modalohr", "CargoBeamer" and "Niederflurwagen" .

During a rolling-highway journey, if the drivers accompany the trailer, they are accommodated in a passenger car or a sleeping car. At both ends of the rail link there are purpose-built terminals that allow the train to be easily loaded and unloaded.

🔗 International relations 🔗 Food and drink

Culinary diplomacy, gastrodiplomacy or food diplomacy is a type of cultural diplomacy, which itself is a subset of public diplomacy. Its basic premise is that "the easiest way to win hearts and minds is through the stomach". Official government-sponsored culinary diplomacy programs have been established in Taiwan, Thailand, South Korea, Malaysia, Peru, the United States, Cambodia, Japan, Scandinavia, Australia and Uzbekistan.