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Coroutine
Coroutines are computer program components that allow execution to be suspended and resumed, generalizing subroutines for cooperative multitasking. Coroutines are well-suited for implementing familiar program components such as cooperative tasks, exceptions, event loops, iterators, infinite lists and pipes. They have been described as "functions whose execution you can pause". Melvin Conway coined the term ''coroutine'' in 1958 when he applied it to the construction of an assembly program. The first published explanation of the coroutine appeared later, in 1963. Definition and types There is no single precise definition of coroutine. In 1980 Christopher D. Marlin summarized two widely-acknowledged fundamental characteristics of a coroutine: # the values of data local to a coroutine persist between successive calls; # the execution of a coroutine is suspended as control leaves it, only to carry on where it left off when control re-enters the coroutine at some later s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Yield (multithreading)
In computer science, yield is an action that occurs in a computer program during multithreading, of forcing a processor to relinquish control of the current running thread, and sending it to the end of the running queue, of the same scheduling priority. Examples Different programming languages implement yielding in various ways. *pthread_yield() in the language C, a low level implementation, provided by POSIX Threads *std::this_thread::yield() in the language C++, introduced in C++11. * The ''Yield method'' is provided in various object-oriented programming languages with multithreading support, such as C# and Java. OOP languages generally provide class abstractions for thread objects. *yield in Kotlin *sched_yield() in the C standard library, which causes the calling thread to relinquish the CPU. In coroutines Coroutines are a fine-grained concurrency primitive, which may be required to yield explicitly. They may enable specifying another function to take control. Cor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Continuation
In computer science, a continuation is an abstract representation of the control state of a computer program. A continuation implements ( reifies) the program control state, i.e. the continuation is a data structure that represents the computational process at a given point in the process's execution; the created data structure can be accessed by the programming language, instead of being hidden in the runtime environment. Continuations are useful for encoding other control mechanisms in programming languages such as exceptions, generators, coroutines, and so on. The "current continuation" or "continuation of the computation step" is the continuation that, from the perspective of running code, would be derived from the current point in a program's execution. The term ''continuations'' can also be used to refer to first-class continuations, which are constructs that give a programming language the ability to save the execution state at any point and return to that point at a l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Subroutine
In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times. Callable units provide a powerful programming tool. The primary purpose is to allow for the decomposition of a large and/or complicated problem into chunks that have relatively low cognitive load and to assign the chunks meaningful names (unless they are anonymous). Judicious application can reduce the cost of developing and maintaining software, while increasing its quality and reliability. Callable units are present at multiple levels of abstraction in the programming environment. For example, a programmer may write a function in source code that is compiled to machine code that implements similar semantics. There is a callable unit in the source code and an associated one in the machine code, but they are different kinds of callable units with different impl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Pipeline (software)
In software engineering, a pipeline consists of a chain of processing elements ( processes, threads, coroutines, functions, ''etc.''), arranged so that the output of each element is the input of the next. The concept is analogous to a physical pipeline. Usually some amount of buffering is provided between consecutive elements. The information that flows in these pipelines is often a stream of records, bytes, or bits, and the elements of a pipeline may be called filters. This is also called the pipe(s) and filters design pattern which is monolithic. Its advantages are simplicity and low cost while its disadvantages are lack of elasticity, fault tolerance and scalability. Connecting elements into a pipeline is analogous to function composition. Narrowly speaking, a pipeline is linear and one-directional, though sometimes the term is applied to more general flows. For example, a primarily one-directional pipeline may have some communication in the other direction, known as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Tail Call
In computer science, a tail call is a subroutine call performed as the final action of a procedure. If the target of a tail is the same subroutine, the subroutine is said to be tail recursive, which is a special case of direct recursion. Tail recursion (or tail-end recursion) is particularly useful, and is often easy to optimize in implementations. Tail calls can be implemented without adding a new stack frame to the call stack. Most of the frame of the current procedure is no longer needed, and can be replaced by the frame of the tail call, modified as appropriate (similar to overlay for processes, but for function calls). The program can then jump to the called subroutine. Producing such code instead of a standard call sequence is called tail-call elimination or tail-call optimization. Tail-call elimination allows procedure calls in tail position to be implemented as efficiently as goto statements, thus allowing efficient structured programming. In the words of Guy L. Steele, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Mutual Recursion
In mathematics and computer science, mutual recursion is a form of recursion where two mathematical or computational objects, such as functions or datatypes, are defined in terms of each other. Mutual recursion is very common in functional programming and in some problem domains, such as recursive descent parsers, where the datatypes are naturally mutually recursive. Examples Datatypes The most important basic example of a datatype that can be defined by mutual recursion is a tree, which can be defined mutually recursively in terms of a forest (a list of trees). Symbolically: f: [1 ..., t[k t: v f A forest ''f'' consists of a list of trees, while a tree ''t'' consists of a pair of a value ''v'' and a forest ''f'' (its children). This definition is elegant and easy to work with abstractly (such as when proving theorems about properties of trees), as it expresses a tree in simple terms: a list of one type, and a pair of two types. Further, it matches many algorithms on trees, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Trampoline (computing)
In computer programming, the word trampoline has a number of meanings, and is generally associated with jump instructions (i.e. moving to different code paths). Low-level programming Trampolines (sometimes referred to as indirect jump vectors) are memory locations holding addresses pointing to interrupt service routines, I/O routines, etc. Execution jumps into the trampoline and then immediately jumps out, or bounces, hence the term ''trampoline''. They have many uses: * Trampoline can be used to overcome the limitations imposed by a central processing unit (CPU) architecture that expects to always find vectors in fixed locations. * When an operating system is booted on a symmetric multiprocessing (SMP) machine, only one processor, the bootstrap processor, will be active. After the operating system has configured itself, it will instruct the other processors to jump to a piece of trampoline code that will initialize the processors and wait for the operating system to start s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Critical Sections
In concurrent programming, concurrent accesses to shared resources can lead to unexpected or erroneous behavior. Thus, the parts of the program where the shared resource is accessed need to be protected in ways that avoid the concurrent access. One way to do so is known as a critical section or critical region. This protected section cannot be entered by more than one process or thread at a time; others are suspended until the first leaves the critical section. Typically, the critical section accesses a shared resource, such as a data structure, peripheral device, or network connection, that would not operate correctly in the context of multiple concurrent accesses. Need for critical sections Different code or processes may consist of the same variable or other resources that must be read or written but whose results depend on the order in which the actions occur. For example, if a variable is to be read by process A, and process B must write to the variable at the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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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] |
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Mutex
In computer science, a lock or mutex (from mutual exclusion) is a synchronization primitive that prevents state from being modified or accessed by multiple threads of execution at once. Locks enforce mutual exclusion concurrency control policies, and with a variety of possible methods there exist multiple unique implementations for different applications. Types Generally, locks are ''advisory locks'', where each thread cooperates by acquiring the lock before accessing the corresponding data. Some systems also implement ''mandatory locks'', where attempting unauthorized access to a locked resource will force an exception in the entity attempting to make the access. The simplest type of lock is a binary semaphore. It provides exclusive access to the locked data. Other schemes also provide shared access for reading data. Other widely implemented access modes are exclusive, intend-to-exclude and intend-to-upgrade. Another way to classify locks is by what happens when the lock stra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Blocking (computing)
In computing, a process that is blocked is waiting for some event, such as a resource becoming available or the completion of an I/O operation. Once the event occurs for which the process is waiting ("is blocked on"), the process is advanced from blocked state to an imminent one, such as runnable. In a multitasking computer system, individual tasks, or threads of execution, must share the resources of the system. Shared resources include: the CPU, network and network interfaces, memory and disk. When one task is using a resource, it is generally not possible, or desirable, for another task to access it. The techniques of mutual exclusion are used to prevent this concurrent use. When the other task is blocked, it is unable to execute until the first task has finished using the shared resource. Programming languages and scheduling algorithms are designed to minimize the over-all effect of blocking. A process that blocks may prevent local work-tasks from progressing. In thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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System Calls
In computing, a system call (syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, accessing a hard disk drive or accessing the device's camera), creation and execution of new processes, and communication with integral kernel services such as process scheduling. System calls provide an essential interface between a process and the operating system. In most systems, system calls can only be made from userspace processes, while in some systems, OS/360 and successors for example, privileged system code also issues system calls. For embedded systems, system calls typically do not change the privilege mode of the CPU. Privileges The architecture of most modern processors, with the exception of some embedded systems, involves a security model. For example, the '' rings'' model specifies multiple privilege levels under which software may be ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |