Wave-formed ripple Wave-formed ripple In sedimentology, wave-formed ripples or wave-formed ripple marks are a feature of sediments (sandstones, limestones, siltstones) and dunes. These ripple marks are often characterised (and thus distinguished from current ripples) by symmetric cross sections and long relatively straight crests, which may commonly bifurcate. Commonly, these crests can be truncated by subsequent flows. Their wavelength (periodicity) depends on the sediment grain size, water depth and water-particle orbits in the waves. On tidal flats the pattern of wave-formed ripples may be complicated, as a product of changing depth and wind and tidal runoff directions. Symmetrical ripples are commonly found in
Distance oracle auxiliary data structure. A simple data structure that achieves this goal is a "matrix" which specifies, for each pair of nodes, the distance between them. This structure allows us to answer queries in constant time formula_2, but requires formula_3 extra space. It can be initialized in time formula_4 using an all-pairs shortest paths algorithm, such as the Floyd–Warshall algorithm. A DO lies between these two extremes. It uses less than formula_3 space in order to answer queries in less than formula_1 time. Most DOs have to compromise on accuracy, i.e. they don't return the accurate distance but rather a constant-factor