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Parallel Efficiency
In computer architecture, speedup is a number that measures the relative performance of two systems processing the same problem. More technically, it is the improvement in speed of execution of a task executed on two similar architectures with different resources. The notion of speedup was established by Amdahl's law, which was particularly focused on parallel processing. However, speedup can be used more generally to show the effect on performance after any resource enhancement. Definitions Speedup can be defined for two different types of quantities: '' latency'' and ''throughput''. ''Latency'' of an architecture is the reciprocal of the execution speed of a task: : L = \frac = \frac, where * ''v'' is the execution speed of the task; * ''T'' is the execution time of the task; * ''W'' is the execution workload of the task. ''Throughput'' of an architecture is the execution rate of a task: : Q = \rho vA = \frac = \frac, where * ''ρ'' is the execution density (e.g., the number ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Architecture
In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, the description may include the instruction set architecture design, microarchitecture design, logic design, and implementation. History The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace, describing the analytical engine. When building the computer Z1 in 1936, Konrad Zuse described in two patent applications for his future projects that machine instructions could be stored in the same storage used for data, i.e., the stored-program concept. Two other early and important examples are: * John von Neumann's 1945 paper, First Draft of a Report on the EDVAC, which described an organization of logical elements; and *Alan Turing's more detailed ''Proposed Electronic Calculator'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instructions Per Cycle
In computer architecture, instructions per cycle (IPC), commonly called instructions per clock is one aspect of a processor's performance: the average number of instructions executed for each clock cycle. It is the multiplicative inverse of cycles per instruction. John L. Hennessy, David A. Patterson.Computer architecture: a quantitative approach. 2007. Explanation While early generations of CPUs carried out all the steps to execute an instruction sequentially, modern CPUs can do many things in parallel. As it is impossible to just keep doubling the speed of the clock, instruction pipelining and superscalar processor design have evolved so CPUs can use a variety of execution units in parallel - looking ahead through the incoming instructions in order to optimise them. This leads to the ''instructions per cycle completed'' being much higher than 1 and is responsible for much of the speed improvements in subsequent CPU generations. Calculation of IPC The calculation of IPC is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallel Slowdown
Parallel slowdown is a phenomenon in parallel computing where parallelization of a parallel algorithm beyond a certain point causes the program to run slower (take more time to run to completion). Parallel slowdown is typically the result of a communications bottleneck. As more processor nodes are added, each processing node spends progressively more time doing communication than useful processing. At some point, the communications overhead created by adding another processing node surpasses the increased processing power that node provides, and parallel slowdown occurs. Parallel slowdown occurs when the algorithm requires significant communication, particularly of intermediate results. Some problems, known as embarrassingly parallel problems, do not require such communication, and thus are not affected by slowdown. References {{reflist See also *Mythical man month ''The Mythical Man-Month: Essays on Software Engineering'' is a book on software engineering and proje ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karp–Flatt Metric
The Karp–Flatt metric is a measure of parallelization of code in parallel processor systems. This metric exists in addition to Amdahl's law and Gustafson's law as an indication of the extent to which a particular computer code is parallelized. It was proposed by Alan H. Karp and Horace P. Flatt in 1990. Description Given a parallel computation exhibiting speedup \psi on p processors, where p > 1, the experimentally determined serial fraction e is defined to be the Karp–Flatt Metric viz: :e = \frac The lower the value of e, the better the parallelization. Justification There are many ways to measure the performance of a parallel algorithm running on a parallel processor. The Karp–Flatt metric defines a metric which reveals aspects of the performance that are not easily discerned from other metrics. A pseudo-"derivation" of sorts follows from Amdahl's Law, which can be written as: :T(p) = T_s + \frac Where: *T(p) is the total time taken for code execution in a p-processor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brooks's Law
Brooks' law is an observation about software project management according to which adding manpower to software project that is behind schedule delays it even longer.Frederick P. Brooks, Jr. ''The Mythical Man-Month''. 1995 975 Addison-Wesley. It was coined by Fred Brooks in his 1975 book ''The Mythical Man-Month''. According to Brooks, under certain conditions, an incremental person when added to a project makes it take more, not less time. Explanations According to Brooks himself, the law is an "outrageous oversimplification", but it captures the general rule. Brooks points to the main factors that explain why it works this way: # It takes some time for the people added to a project to become productive. Brooks calls this the "ramp up" time. Software projects are complex engineering endeavors, and new workers on the project must first become educated about the work that has preceded them; this education requires diverting resources already working on the project, temporarily dim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backtracking
Backtracking is a class of algorithms for finding solutions to some computational problems, notably constraint satisfaction problems, that incrementally builds candidates to the solutions, and abandons a candidate ("backtracks") as soon as it determines that the candidate cannot possibly be completed to a valid solution. The classic textbook example of the use of backtracking is the eight queens puzzle, that asks for all arrangements of eight chess queens on a standard chessboard so that no queen attacks any other. In the common backtracking approach, the partial candidates are arrangements of ''k'' queens in the first ''k'' rows of the board, all in different rows and columns. Any partial solution that contains two mutually attacking queens can be abandoned. Backtracking can be applied only for problems which admit the concept of a "partial candidate solution" and a relatively quick test of whether it can possibly be completed to a valid solution. It is useless, for example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BLAST
Blast or The Blast may refer to: * Explosion, a rapid increase in volume and release of energy in an extreme manner *Detonation, an exothermic front accelerating through a medium that eventually drives a shock front Film * ''Blast'' (1997 film), starring Andrew Divoff * ''Blast'' (2000 film), starring Liesel Matthews * ''Blast'' (2004 film), an action comedy film * ''Blast!'' (1972 film) or ''The Final Comedown'', an American drama * ''BLAST!'' (2008 film), a documentary about the BLAST telescope * '' A Blast'', a 2014 film directed by Syllas Tzoumerkas Magazines * ''Blast'' (magazine), a 1914–15 literary magazine of the Vorticist movement * ''Blast'' (U.S. magazine), a 1933–34 American short-story magazine * ''The Blast'' (magazine), a 1916–17 American anarchist periodical Music * Blast (American band), a hardcore punk band * Blast (Russian band), an indie band * ''Blast'' (album), by Holly Johnson, 1989 * ''The Blast'' (album), by Yuvan Shankar Raja, 1999 * " ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Working Set
Working set is a concept in computer science which defines the amount of memory that a process requires in a given time interval. Definition Peter Denning (1968) defines "the working set of information W(t, \tau) of a process at time t to be the collection of information referenced by the process during the process time interval (t - \tau, t)". Typically the units of information in question are considered to be memory pages. This is suggested to be an approximation of the set of pages that the process will access in the future (say during the next \tau time units), and more specifically is suggested to be an indication of what pages ought to be kept in main memory to allow most progress to be made in the execution of that process. Rationale The effect of the choice of what pages to be kept in main memory (as distinct from being ''paged out'' to auxiliary storage) is important: if too many pages of a process are kept in main memory, then fewer other processes can be ready at any ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Hierarchy
In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controlling technologies. Memory hierarchy affects performance in computer architectural design, algorithm predictions, and lower level programming constructs involving locality of reference. Designing for high performance requires considering the restrictions of the memory hierarchy, i.e. the size and capabilities of each component. Each of the various components can be viewed as part of a hierarchy of memories (m1, m2, ..., mn) in which each member mi is typically smaller and faster than the next highest member mi+1 of the hierarchy. To limit waiting by higher levels, a lower level will respond by filling a buffer and then signaling for activating the transfer. There are four major storage levels. * ''Internal'' – Processor registers and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CPU Cache
A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, which stores copies of the data from frequently used main memory locations. Most CPUs have a hierarchy of multiple cache levels (L1, L2, often L3, and rarely even L4), with different instruction-specific and data-specific caches at level 1. The cache memory is typically implemented with static random-access memory (SRAM), in modern CPUs by far the largest part of them by chip area, but SRAM is not always used for all levels (of I- or D-cache), or even any level, sometimes some latter or all levels are implemented with eDRAM. Other types of caches exist (that are not counted towards the "cache size" of the most important caches mentioned above), such as the translation lookaside buffer (TLB) which is part of the memory management unit (MMU) w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallel Computing
Parallel computing is a type of computation in which many calculations or 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, instruction-level, 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 increases must largely come from increasing the number of processors (or cores) on a die, rather than m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scalability
Scalability is the property of a system to handle a growing amount of work by adding resources to the system. In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a package delivery system is scalable because more packages can be delivered by adding more delivery vehicles. However, if all packages had to first pass through a single warehouse for sorting, the system would not be as scalable, because one warehouse can handle only a limited number of packages. In computing, scalability is a characteristic of computers, networks, algorithms, networking protocols, programs and applications. An example is a search engine, which must support increasing numbers of users, and the number of topics it indexes. Webscale is a computer architectural approach that brings the capabilities of large-scale cloud computing companies into enterprise data centers. In mathematics, scalability mostly refers to closure u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
