W1

W1 could refer to:

W1, a postcode district in the W postcode area of London

British NVC community W1 (Salix cinerea - Galium palustre woodland), one of the woodland communities of the British National Vegetation Classification

W-1 tool steel, a water-hardening steel

one of four manuscripts containing the Magnus Liber, or Magnus liber organi, a compilation of medieval music. The term is derived from the Wolfenbüttel library which holds the manuscript (Herzog August Bibliothek).

GN W-1, an electric locomotive built for the Great Northern Railway

LNER Class W1, an experimental locomotive designed by Sir Nigel Gresley for the London and North Eastern Railway

second step of the W0-W6 scale for the classification of meteorites by weathering

Wrestle-1, a Japanese professional wrestling promotion

Windows 1.0

The computational complexity class W[1] in parameterized complexity

Parameterized complexity

In computer science, parameterized complexity is a branch of computational complexity theory that focuses on classifying computational problems according to their inherent difficulty with respect to multiple parameters of the input or output. The complexity of a problem is then measured as a function in those parameters. This allows the classification of NP-hard problems on a finer scale than in the classical setting, where the complexity of a problem is only measured by the number of bits in the input. The first systematic work on parameterized complexity was done by Downey & Fellows (1999).

Under the assumption that P ≠ NP, there exist many natural problems that require superpolynomial running time when complexity is measured in terms of the input size only, but that are computable in a time that is polynomial in the input size and exponential or worse in a parameter $k$ . Hence, if $k$ is fixed at a small value and the growth of the function over $k$ is relatively small then such problems can still be considered "tractable" despite their traditional classification as "intractable".