|
Contraction Hierarchies
In computer science, the method of contraction hierarchies is a speed-up technique for finding the shortest path in a graph. The most intuitive applications are car-navigation systems: a user wants to drive from A to B using the quickest possible route. The metric optimized here is the travel time. Intersections are represented by vertices, the road sections connecting them by edges. The edge weights represent the time it takes to drive along this segment of the road. A path from A to B is a sequence of edges (road sections); the shortest path is the one with the minimal sum of edge weights among all possible paths. The shortest path in a graph can be computed using Dijkstra's algorithm but, given that road networks consist of tens of millions of vertices, this is impractical. Contraction hierarchies is a speed-up method optimized to exploit properties of graphs representing road networks. The speed-up is achieved by creating shortcuts in a preprocessing phase which are then used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computational Complexity Theory
In theoretical computer science and mathematics, computational complexity theory focuses on classifying computational problems according to their resource usage, and explores the relationships between these classifications. A computational problem is a task solved by a computer. A computation problem is solvable by mechanical application of mathematical steps, such as an algorithm. A problem is regarded as inherently difficult if its solution requires significant resources, whatever the algorithm used. The theory formalizes this intuition, by introducing mathematical models of computation to study these problems and quantifying their computational complexity, i.e., the amount of resources needed to solve them, such as time and storage. Other measures of complexity are also used, such as the amount of communication (used in communication complexity), the number of logic gate, gates in a circuit (used in circuit complexity) and the number of processors (used in parallel computing). O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Highway Dimension
The highway dimension is a graph parameter modelling transportation networks, such as road networks or public transportation networks. It was first formally defined by Abraham et al. based on the observation by Bast et al. that any road network has a sparse set of "transit nodes", such that driving from a point A to a sufficiently far away point B along the shortest route will always pass through one of these transit nodes. It has also been proposed that the highway dimension captures the properties of public transportation networks well, given that longer routes using busses, trains, or airplanes will typically be serviced by larger transit hubs (stations and airports). This relates to the spoke–hub distribution paradigm in transport topology optimization. Definitions Several definitions of the highway dimension exist, although the one based on approximate shortest paths given below is the most general one. Each definition of the highway dimension uses a hitting set of a cer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Vehicle
An electric vehicle (EV) is a motor vehicle whose propulsion is powered fully or mostly by electricity. EVs encompass a wide range of transportation modes, including road vehicle, road and rail vehicles, electric boats and Submersible, submersibles, electric aircraft and electrically powered spacecraft propulsion, electric spacecraft. Early electric vehicles first came into existence in the late 19th century, when the Second Industrial Revolution brought forth electrification and mass utilization of DC motor, DC and AC motor, AC electric motors. Using electricity was among the preferred methods for motor vehicle propulsion as it provided a level of quietness, comfort and ease of operation that could not be achieved by the gasoline engine cars of the time, but range anxiety due to the limited energy storage offered by history of the battery, contemporary battery technologies hindered any mass adoption of private electric vehicles throughout the 20th century. Internal combustion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache (computing)
In computing, a cache ( ) is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A cache hit occurs when the requested data can be found in a cache, while a cache miss occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing a result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs. To be cost-effective, caches must be relatively small. Nevertheless, caches are effective in many areas of computing because typical Application software, computer applications access data with a high degree of locality of reference. Such access patterns exhibit temporal locality, where data is requested that has been recently requested, and spatial locality, where data is requested that is stored near dat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallel Computing
Parallel computing is a type of computing, computation in which many calculations or Process (computing), processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different forms of parallel computing: Bit-level parallelism, bit-level, Instruction-level parallelism, instruction-level, Data parallelism, data, and task parallelism. Parallelism has long been employed in high-performance computing, but has gained broader interest due to the physical constraints preventing frequency scaling.S.V. Adve ''et al.'' (November 2008)"Parallel Computing Research at Illinois: The UPCRC Agenda" (PDF). Parallel@Illinois, University of Illinois at Urbana-Champaign. "The main techniques for these performance benefits—increased clock frequency and smarter but increasingly complex architectures—are now hitting the so-called power wall. The computer industry has accepted that future performance inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geographical Distance
Geographical distance or geodetic distance is the distance measured along the surface of the Earth, or the shortest arch length. The formulae in this article calculate distances between points which are defined by geographical coordinates in terms of latitude and longitude. This distance is an element in solving the Geodesy#Geodetic problems, second (inverse) geodetic problem. Introduction Calculating the distance between geographical coordinates is based on some level of abstraction; it does not provide an ''exact'' distance, which is unattainable if one attempted to account for every irregularity in the surface of the Earth. Common abstractions for the surface between two geographic points are: *Flat surface; *Spherical surface; *Ellipsoidal surface. All abstractions above ignore changes in elevation. Calculation of distances which account for changes in elevation relative to the idealized surface are not discussed in this article. Classification of Formulae based on Appr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Route Prediction
Route or routes may refer to: * Air route, route structure or airway * GPS route, a series of one or more GPS waypoints * Route (gridiron football), a path run by a wide receiver * Route (command), a program used to configure the routing table * Route, County Antrim, an area in Northern Ireland * Routes, Seine-Maritime, a commune in Seine-Maritime, France * ''Routes'', a 2003 video game by Leaf See also * Acronyms and abbreviations in avionics * Path (other) * Rout, a disorderly retreat of military units from the field of battle * Route number or road number * Router (other) * Router (woodworking) * Routing (other) * The Route (other) * Routing table * Scenic route, a thoroughfare designated as scenic based on the scenery through which it passes * Trade route A trade route is a logistical network identified as a series of pathways and stoppages used for the commercial transport of cargo. The term can also be used to refer to trade over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Simulation
Traffic simulation or the simulation of transportation systems is the computer simulation, mathematical modeling of transportation systems (e.g., freeway junctions, arterial routes, roundabouts, downtown grid systems, etc.) through the application of computer software to better help plan, design, and operate transportation systems. Simulation of transportation systems started in the 1950s, and is an important area of discipline in traffic engineering (transportation), traffic engineering and transportation planning today. Various national and local transportation agencies, academic institutions and consulting firms use simulation to aid in their management of transportation networks. Simulation in transportation is important because it can study models too complicated for analytical or numerical treatment, can be used for experimental studies, can study detailed relations that might be lost in analytical or numerical treatment and can produce attractive visual demonstrations of prese ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Positioning System
The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephone or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls, and maintains the GPS system, it is freely accessible to anyone with a GPS receiver. Overview The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was launched in 1978 an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Search Space Of CH
Searching may refer to: Music * " Searchin", a 1957 song originally performed by The Coasters * "Searching" (China Black song), a 1991 song by China Black * "Searchin" (CeCe Peniston song), a 1993 song by CeCe Peniston * " Searchin' (I Gotta Find a Man)", a 1983 dance song by Hazell Dean * "Searching" (INXS song), a 1997 song by INXS * "Searching" (Pete Rock & CL Smooth song), a 1995 song from the Pete Rock & CL Smooth album ''The Main Ingredient'' * ''Searching'', a 2013 album by Jay Diggins * "Searching", a 1980 single by Change * "Searching", a 2004 song by Joe Satriani from his album '' Is There Love in Space?'' * "Searchin", a 1981 song on the Blackfoot album ''Marauder'' * "Searching", a 1976 song by Lynyrd Skynyrd from the album '' Gimme Back My Bullets'' * "Searching", a 1976 song by Roy Ayers from the album '' Vibrations'' * "Searchin", a 2003 song by Brant Bjork from the album '' Keep Your Cool'' * "Searchin", a 1996 song by Eminem from his album '' Infinite'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nested Dissection
In numerical analysis, nested dissection is a divide and conquer heuristic for the solution of sparse symmetric systems of linear equations based on graph partitioning. Nested dissection was introduced by ; the name was suggested by Garrett Birkhoff. Nested dissection consists of the following steps: *Form an undirected graph in which the vertices represent rows and columns of the system of linear equations, and an edge represents a nonzero entry in the sparse matrix representing the system. * Recursively partition the graph into subgraphs using separators, small subsets of vertices the removal of which allows the graph to be partitioned into subgraphs with at most a constant fraction of the number of vertices. *Perform Cholesky decomposition (a variant of Gaussian elimination for symmetric matrices), ordering the elimination of the variables by the recursive structure of the partition: each of the two subgraphs formed by removing the separator is eliminated first, and then the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
