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Double-checked Locking
In software engineering, double-checked locking (also known as "double-checked locking optimization") is a software design pattern used to reduce the overhead of acquiring a lock by testing the locking criterion (the "lock hint") before acquiring the lock. Locking occurs only if the locking criterion check indicates that locking is required. The pattern, when implemented in some language/hardware combinations, can be unsafe. At times, it can be considered an anti-pattern.David Bacon et alThe "Double-Checked Locking is Broken" Declaration It is typically used to reduce locking overhead when implementing "lazy initialization" in a multi-threaded environment, especially as part of the Singleton pattern. Lazy initialization avoids initializing a value until the first time it is accessed. Usage in C++11 For the singleton pattern, double-checked locking is not needed: Singleton& GetInstance() C++11 and beyond also provide a built-in double-checked locking pattern in the form of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Engineering
Software engineering is a systematic engineering approach to software development. A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' programmer'' is sometimes used as a synonym, but may also lack connotations of engineering education or skills. Engineering techniques are used to inform the software development process which involves the definition, implementation, assessment, measurement, management, change, and improvement of the software life cycle process itself. It heavily uses software configuration management which is about systematically controlling changes to the configuration, and maintaining the integrity and traceability of the configuration and code throughout the system life cycle. Modern processes use software versioning. History Beginning in the 1960s, software engineering was seen as its own type of engineering. Additionally, the development of soft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volatile Variable
In computer programming, particularly in the C, C++, C#, and Java programming languages, the volatile keyword indicates that a value may change between different accesses, even if it does not appear to be modified. This keyword prevents an optimizing compiler from optimizing away subsequent reads or writes and thus incorrectly reusing a stale value or omitting writes. Volatile values primarily arise in hardware access (memory-mapped I/O), where reading from or writing to memory is used to communicate with peripheral devices, and in threading, where a different thread may have modified a value. Despite being a common keyword, the behavior of volatile differs significantly between programming languages, and is easily misunderstood. In C and C++, it is a type qualifier, like const, and is a property of the '' type''. Furthermore, in C and C++ it does ''not'' work in most threading scenarios, and that use is discouraged. In Java and C#, it is a property of a variable and indicates t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concurrency Control
In information technology and computer science, especially in the fields of computer programming, operating systems, multiprocessors, and databases, concurrency control ensures that correct results for Concurrent computing, concurrent operations are generated, while getting those results as quickly as possible. Computer systems, both software and computer hardware, hardware, consist of modules, or components. Each component is designed to operate correctly, i.e., to obey or to meet certain consistency rules. When components that operate concurrently interact by messaging or by sharing accessed data (in Computer memory, memory or Computer data storage, storage), a certain component's consistency may be violated by another component. The general area of concurrency control provides rules, methods, design methodologies, and Scientific theory, theories to maintain the consistency of components operating concurrently while interacting, and thus the consistency and correctness of the who ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allen Holub
Allen, Allen's or Allens may refer to: Buildings * Allen Arena, an indoor arena at Lipscomb University in Nashville, Tennessee * Allen Center, a skyscraper complex in downtown Houston, Texas * Allen Fieldhouse, an indoor sports arena on the University of Kansas campus in Lawrence * Allen House (other) * Allen Power Plant (other) Businesses *Allen (brand), an American tool company *Allen's, an Australian brand of confectionery *Allens (law firm), an Australian law firm formerly known as Allens Arthur Robinson *Allen's (restaurant), a former hamburger joint and nightclub in Athens, Georgia, United States *Allen & Company LLC, a small, privately held investment bank *Allens of Mayfair, a butcher shop in London from 1830 to 2015 *Allens Boots, a retail store in Austin, Texas * Allens, Inc., a brand of canned vegetables based in Arkansas, US, now owned by Del Monte Foods * Allen's department store, a.k.a. Allen's, George Allen, Inc., Philadelphia, USA People * Allen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brian Goetz
Brian (sometimes spelled Bryan in English) is a male given name of Irish and Breton origin, as well as a surname of Occitan origin. It is common in the English-speaking world. It is possible that the name is derived from an Old Celtic word meaning "high" or "noble". For example, the element ''bre'' means "hill"; which could be transferred to mean "eminence" or "exalted one". The name is quite popular in Ireland, on account of Brian Boru, a 10th-century High King of Ireland. The name was also quite popular in East Anglia during the Middle Ages. This is because the name was introduced to England by Bretons following the Norman Conquest. Bretons also settled in Ireland along with the Normans in the 12th century, and 'their' name was mingled with the 'Irish' version. Also, in the north-west of England, the 'Irish' name was introduced by Scandinavian settlers from Ireland. Within the Gaelic speaking areas of Scotland, the name was at first only used by professional families of Irish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andrei Alexandrescu
Andrei Alexandrescu (born 1969) is a Romanian-American C++ and D language programmer and author. He is particularly known for his pioneering work on policy-based design implemented via template metaprogramming. These ideas are articulated in his book ''Modern C++ Design'' and were first implemented in his programming library, Loki. He also implemented the " move constructors" concept in his MOJO library. He contributed to the ''C/C++ Users Journal'' under the byline "Generic". Alexandrescu worked as a research scientist at Facebook, before departing the company in August 2015 in order to focus on developing the D programming language. He became an American citizen in August 2014. Education and career Alexandrescu received a B.S. degree in Electrical Engineering from Polytechnic University of Bucharest (''Universitatea Politehnica din București'') in July 1994. His first article was published in the ''C/C++ Users Journal'' in September 1998. He was a program manager for Ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scott Meyers
Scott Douglas Meyers (born April 9, 1959) is an American author and software consultant, specializing in the C++ computer programming language. He is known for his ''Effective C++'' book series. During his career, he was a frequent speaker at conferences and trade shows. Biography He holds a Ph.D. in computer science from Brown University and an M.S. in computer science from Stanford University. He conceived and, with Herb Sutter, Andrei Alexandrescu, Dan Saks, and Steve Dewhurst, co-organized and presented the boutique (limited-attendance) conference, ''The C++ Seminar'', which took place three times in 2001-2002. He also conceived and, with Sutter and Alexandrescu, co-organized and presented another boutique conference, ''C++ and Beyond'' annually in 2010-2014. Meyers has expressed opposition to asking programmers to solve design or programming problems during job interviews:"I hate anything that asks me to design on the spot. That's asking to demonstrate a skill rarely requir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initialization-on-demand Holder Idiom
In software engineering, the initialization-on-demand holder (design pattern) idiom is a lazy-loaded singleton. In all versions of Java, the idiom enables a safe, highly concurrent lazy initialization of static fields with good performance. public class Something The implementation of the idiom relies on the initialization phase of execution within the Java Virtual Machine (JVM) as specified by the Java Language Specification (JLS). When the class Something is loaded by the JVM, the class goes through initialization. Since the class does not have any static variables to initialize, the initialization completes trivially. The static class definition LazyHolder within it is ''not'' initialized until the JVM determines that LazyHolder must be executed. The static class LazyHolder is only executed when the static method getInstance is invoked on the class Something, and the first time this happens the JVM will load and initialize the LazyHolder class. The initialization of the LazyH ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programming Idiom
In computer programming, a programming idiom or code idiom is a group of code fragments sharing an equivalent semantic role, which recurs frequently across software projects often expressing a special feature of a recurring construct in one or more programming languages or libraries. Developers recognize programming idioms by associating and giving meaning (semantic role) to one or more syntactical expressions within code snippets (code fragments). The idiom can be seen as a concept underlying a pattern in code, which is represented in implementation by contiguous or scattered code fragments. These fragments are available in several programming languages, frameworks or even libraries. Generally speaking, a programming idiom's semantic role is a natural language expression of a simple task, algorithm, or data structure that is not a built-in feature in the programming language being used, or, conversely, the use of an unusual or notable feature that ''is'' built into a programming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Test And Test-and-set
In computer science, the test-and-set CPU instruction is used to implement mutual exclusion in multiprocessor environments. Although a correct lock can be implemented with test-and-set, it can lead to resource contention in busy lock (caused by bus locking and cache invalidation when test-and-set operation needs to access memory atomically). To lower the overhead a more elaborate locking protocol test and test-and-set is used. Given a lock: ''boolean'' locked := false ''// shared lock variable'' Entry protocol is: procedure EnterCritical() Exit protocol is: procedure ExitCritical() The entry protocol uses normal memory reads to wait for the lock to become free. Test-and-set is only used to try to get the lock when normal memory read says it's free. Thus the expensive atomic memory operations happen less often than in a simple spin around test-and-set. If the programming language used supports short-circuit evaluation, the entry protocol could be implemented as: proced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |