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PTAS
PTAS or Ptas may refer to: * Polynomial-time approximation scheme, an approximation algorithm in computer science * Pesetas, Spanish currency *PTAS reduction, an approximation-preserving reduction in computational complexity theory *Preferential trading area A preferential trade area (also preferential trade agreement, PTA) is a trading bloc that gives preferential access to certain products from the participating countries. This is done by reducing tariffs but not by abolishing them completely. It ..., another term for a trade bloc See also * PTA (other) {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polynomial-time Approximation Scheme
In computer science (particularly algorithmics), a polynomial-time approximation scheme (PTAS) is a type of approximation algorithm for optimization problems (most often, NP-hard optimization problems). A PTAS is an algorithm which takes an instance of an optimization problem and a parameter and produces a solution that is within a factor of being optimal (or for maximization problems). For example, for the Euclidean traveling salesman problem, a PTAS would produce a tour with length at most , with being the length of the shortest tour. The running time of a PTAS is required to be polynomial in the problem size for every fixed ε, but can be different for different ε. Thus an algorithm running in time or even counts as a PTAS. Variants Deterministic A practical problem with PTAS algorithms is that the exponent of the polynomial could increase dramatically as ε shrinks, for example if the runtime is . One way of addressing this is to define the efficient polynomial-time a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spanish Peseta
The peseta (, ), * ca, pesseta, was the currency of Spain between 1868 and 2002. Along with the French franc, it was also a ''de facto'' currency used in Andorra (which had no national currency with legal tender). Etymology The name of the currency originally comes from ''peceta'', a Catalan diminutive form of the (Catalan) word ''peça'' (lit. ''piece'', i.e. a coin), not from the Spanish ''peso'' (lit. ''weight''). The word ''peseta'' has been known as early as 1737 to colloquially refer to the coin worth 2 ''reales provincial'' or of a peso. Coins denominated in "pesetas" were briefly issued in 1808 in Barcelona under French occupation; see Catalan peseta. Symbol Traditionally, there was never a single symbol or special character for the Spanish peseta. Common abbreviations were "Pta" (plural: "Pts), "Pt", and "Ptas". A common way of representing amounts of pesetas in print was using superior letters: "Pta" and "Pts". Common Spanish models of mechanical typewrit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PTAS Reduction
In computational complexity theory, a PTAS reduction is an approximation-preserving reduction that is often used to perform reductions between solutions to optimization problems. It preserves the property that a problem has a polynomial time approximation scheme (PTAS) and is used to define completeness for certain classes of optimization problems such as APX. Notationally, if there is a PTAS reduction from a problem A to a problem B, we write \text \leq_ \text. With ordinary polynomial-time many-one reductions, if we can describe a reduction from a problem A to a problem B, then any polynomial-time solution for B can be composed with that reduction to obtain a polynomial-time solution for the problem A. Similarly, our goal in defining PTAS reductions is so that given a PTAS reduction from an optimization problem A to a problem B, a PTAS for B can be composed with the reduction to obtain a PTAS for the problem A. Definition Formally, we define a PTAS reduction from A to B using th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preferential Trading Area
A preferential trade area (also preferential trade agreement, PTA) is a trading bloc that gives preferential access to certain products from the participating countries. This is done by reducing tariffs but not by abolishing them completely. It is the first stage of economic integration. These tariff preferences have created numerous departures from the normal trade relations principle, namely that World Trade Organization (WTO) members should apply the same tariff to imports from other WTO members. With the recent multiplication of bilateral PTAs and the emergence of Mega-PTAs (wide regional trade agreements such as the Transatlantic Trade and Investment Partnership (TTIP) or Trans Pacific Partnership (TPP)), a global trade system exclusively managed within the framework of the WTO now seems unrealistic and the interactions between trade systems have to be taken into account. The increased complexity of the international trade system generated by the multiplication of PTAs s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
