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A compare-and-swap operation is an atomic version of the following pseudocode, where * denotes access through a pointer: [1]. function cas(p: pointer to int, old: int, new: int) is if *p ≠ old return false *p ← new return true
The following C code examples illustrate two threads that share a global integer i. The first thread uses busy-waiting to check for a change in the value of i : #include <pthread.h> #include <stdatomic.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> /* i is global, so it is visible to all functions.
Strings are immutable; built-in operators and keywords (rather than functions) provide concatenation, comparison, and UTF-8 encoding/decoding. [60] Record types can be defined with the struct keyword. [61] For each type T and each non-negative integer constant n, there is an array type denoted [n]T; arrays of differing lengths are thus of ...
The modified V and P operations are as follows, using square brackets to indicate atomic operations, i.e., operations that appear indivisible to other processes: function V(semaphore S, integer I): [S ← S + I] function P(semaphore S, integer I): repeat: [if S ≥ I: S ← S − I break]
I/O is inherently impure: input operations undermine referential transparency, and output operations create side effects.Nevertheless, there is a sense in which a function can perform input or output and still be pure, if the sequence of operations on the relevant I/O devices is modeled explicitly as both an argument and a result, and I/O operations are taken to fail when the input sequence ...
Integer addition, for example, can be performed as a single machine instruction, and some offer specific instructions to process sequences of characters with a single instruction. [7] But the choice of primitive data type may affect performance, for example it is faster using SIMD operations and data types to operate on an array of floats.
In computer science, the fetch-and-add (FAA) CPU instruction atomically increments the contents of a memory location by a specified value.. That is, fetch-and-add performs the following operation: increment the value at address x by a, where x is a memory location and a is some value, and return the original value at x.
In computer science, a literal is a textual representation (notation) of a value as it is written in source code. [1] [2] Almost all programming languages have notations for atomic values such as integers, floating-point numbers, and strings, and usually for Booleans and characters; some also have notations for elements of enumerated types and compound values such as arrays, records, and objects.