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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 original form of the pattern, appearing in ''Pattern Languages of Program Design 3'', has data races, depending on the memory model in use, and it is hard to get right. Some consider it to be an anti-pattern. There are valid forms of the pattern, including the use of the keyword in Java and explicit memory barriers in C++.David Bacon et alThe "Double-Checked Locking is Broken" Declaration The pattern 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 a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Engineering
Software engineering is a branch of both computer science and engineering focused on designing, developing, testing, and maintaining Application software, software applications. It involves applying engineering design process, engineering principles and computer programming expertise to develop software systems that meet user needs. The terms ''programmer'' and ''coder'' overlap ''software engineer'', but they imply only the construction aspect of a typical software engineer workload. A software engineer applies a software development process, which involves defining, Implementation, implementing, Software testing, testing, Project management, managing, and Software maintenance, maintaining software systems, as well as developing the software development process itself. History Beginning in the 1960s, software engineering was recognized as a separate field of engineering. The development of software engineering was seen as a struggle. Problems included software that was over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volatile Variable
In computer programming, a variable is said to be ''volatile'' if its value can be read or modified asynchronously by something other than the current thread of execution. The value of a volatile variable may spontaneously change for reasons such as: sharing values with other threads; sharing values with asynchronous signal handlers; accessing hardware devices via memory-mapped I/O (where you can send and receive messages from peripheral devices by reading from and writing to memory). Support for these use cases varies considerably among the programming languages that have the volatile keyword. Volatility can have implications regarding function calling conventions and how variables are stored, accessed and cached. In C and C++ In C and C++, volatile is a type qualifier, like const, and is a part of a type (e.g. the type of a variable or field). The behavior of the volatile keyword in C and C++ is sometimes given in terms of suppressing optimizations of an optimizing ... [...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 operations are generated, while getting those results as quickly as possible. Computer systems, both software and 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 memory or storage), a certain component's consistency may be violated by another component. The general area of concurrency control provides rules, methods, design methodologies, and theories to maintain the consistency of components operating concurrently while interacting, and thus the consistency and correctness of the whole system. Introducing concurrency control into a system means applying operation constraints ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allen Holub
Allen I. Holub (born 1955) is a computer author who was published in ''Dr. Dobb's Journal'' in the 1980s and then again in the 2010s. He also wrote for ''SD Times''. His 1990 book ''Compiler Design in C'' was praised as an accessible reference. He is also a teacher, consultant, and speaker. Career Allen Holub received double Bachelor of Arts degrees from the University of California, Berkeley, in Computer Science and Medieval European History. In 1982, he became an instructor for the University of California Berkeley Extension, where he has continued teaching periodically to the present day. He started his consulting company "Holub Associates" in 1983, which has also continued to the present day. Holub was the Chan-Norris Distinguished Visiting Professor of Computer Science at Mills College for the 2021-2022 academic year, teaching a computer science elective course among other duties. Writing Holub is a prolific author and has written many books and articles. His "C Chest" ... [...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 Iris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andrei Alexandrescu
Tudor Andrei Cristian 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 (C++), Loki. He also implemented the "move constructors" concept in his MOJO library. He contributed to the ''C/C++ Users Journal'' under the byline "Generic". 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 Netzip, Inc. from April 1999 until February 2000. When the company was acquired by RealNetworks, Inc., he served there as a development man ... [...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 req ... [...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 Lazy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programming Idiom
In computer programming, a programming idiom, code idiom or simply idiom is a code fragment having a semantic role which recurs frequently across software projects. It often expresses a special feature of a recurring construct in one or more programming languages, frameworks or libraries. This definition is rooted in the linguistic definition of "idiom". The idiom can be seen by developers as an action on a programming concept underlying a pattern in code, which is represented in implementation by contiguous or scattered code snippets. 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 language. Knowing the idioms associated with a programming language and how to use them is an important part of gaining fluency in that language. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Test And Test-and-set
In computer architecture, the test-and-set CPU instruction (or instruction sequence) is designed to implement mutual exclusion in multiprocessor environments. Although a correct lock can be implemented with test-and-set, the ''test and test-and-set'' optimization lowers resource contention caused by bus locking, especially cache coherency protocol overhead on contended locks. Given a lock: ''boolean'' locked := false ''// shared lock variable'' the entry protocol is: procedure EnterCritical() and the exit protocol is: procedure ExitCritical() The difference to the simple test-and-set protocol is the additional spin-loop (the ''test'' in ''test and test-and-set'') at the start of the entry protocol, which utilizes ordinary load instructions. The load in this loop executes with less overhead compared to an atomic operation (resp. a load-exclusive instruction). E.g., on a system utilizing the MESI cache coherency protocol, the cache line being loaded is moved to the S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |