P-class sloop
The P class, nominally described as "patrol boats", was in effect a class of coastal sloops. Twenty-four ships to this design were ordered in May 1915 (numbered P.11 to P.34) and another thirty between February and June 1916 (numbered P.35 to P.64) under the Emergency War Programme for the Royal Navy in the First World War, although ten of the latter group were in December 1916 altered on the stocks before launch for use as decoy Q-ships and were renumbered as PC-class sloops. None were named, although in 1925 P.38 was given the name Spey.
These vessels were designed to replace destroyers in coastal operations, but had twin screws, a very low freeboard, ram bows of hardened steel, a sharply cutaway funnel and a small turning circle. Clearly seen as the linear descendants of the late 19th century steam torpedo boats and coastal destroyers, many were actually fitted with the 14 in torpedo tubes removed from old torpedo boats.
With the survival of a builder's diary by William Bartram, full details of the sea trials of P.23 on 21 June 1916 exist. She worked up to 21.8 knots (40.4 km/h). Bartram's commissioned a model from Sunderland model maker C Crawford & Sons and this model, in the collections of Sunderland Museum and Heritage Service, is stored in the model store of Tyne & Wear Archives & Museums Service at the Discovery Museum.
P class
P class or Class P may refer to:
Computing
Ships and yachts
Railway locomotives
- NZR P class (1876), of 1876
- NZR P class (1885), of 1885
P (complexity)
In computational complexity theory, P, also known as PTIME or DTIME(nO(1)), is one of the most fundamental complexity classes. It contains all decision problems that can be solved by a deterministic Turing machine using a polynomial amount of computation time, or polynomial time.
Cobham's thesis holds that P is the class of computational problems that are "efficiently solvable" or "tractable"; in practice, some problems not known to be in P have practical solutions, and some that are in P do not, but this is a useful rule of thumb.
Definition
A language L is in P if and only if there exists a deterministic Turing machine M, such that
P can also be viewed as a uniform family of boolean circuits. A language L is in P if and only if there exists a polynomial-time uniform family of boolean circuits 
, such that
, 
takes n bits as input and outputs 1 bit
NZR P class (1885)
The P class was a class of steam locomotives built to haul freight trains on the national rail network of New Zealand. The class consisted of ten individual locomotives ordered from the British company of Nasmyth, Wilson and Company in 1885, but miscommunications about the weight limitations imposed on the locomotives meant they did not start work until 1887. This debacle came at a time when the New Zealand Railways Department (NZR) was suffering from a lack of motive power to work on its rapidly expanding network and was part of what prompted a shift towards American and home-grown manufacturers.
The classification of this class as "P" was the first example of the re-use of a classification that had previously been used for an earlier class. The members of the P class of 1876 had been sold to private companies or the Public Works Department, leaving the classification unused. The Railways Department chose to assign it to this class, setting a pattern that was followed with other classes in years to come, with the most prominent example being the A class of 1906 re-using the classification of the A class of 1873.
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