Editing Software design pattern (section)

=== [[Concurrency patterns]] ===
{| class="wikitable"
|-
! Name
! Description
! In ''[[Pattern-Oriented Software Architecture|POSA2]]''<ref name="POSA2">{{cite book
 | first1 = Douglas C.
 | last1 = Schmidt
| first2 = Michael | last2 = Stal | first3 = Hans | last3 = Rohnert | first4 = Frank | last4 = Buschmann
 | date = 2000
 | title = Pattern-Oriented Software Architecture, Volume 2: Patterns for Concurrent and Networked Objects
 | publisher = John Wiley & Sons
 | isbn = 978-0-471-60695-6
}}</ref>
! Other
|-
| [[Active Object]]
| Decouples method execution from method invocation that reside in their own thread of control. The goal is to introduce concurrency, by using [[asynchronous method invocation]] and a [[scheduling (computing)|scheduler]] for handling requests.
| {{yes}}
| {{n/a}}
|-
| [[Balking pattern|Balking]]
| Only execute an action on an object when the object is in a particular state.
| {{no}}
| {{n/a}}
|-
| [[Binding properties pattern|Binding properties]]
| Combining multiple observers to force properties in different objects to be synchronized or coordinated in some way.<ref>[http://c2.com/cgi/wiki?BindingProperties Binding Properties<!-- Bot generated title -->]</ref>
| {{no}}
| {{n/a}}
|-
| [[Compute kernel]]
| The same calculation many times in parallel, differing by integer parameters used with non-branching pointer math into shared arrays, such as [[GPU]]-optimized [[Matrix multiplication]] or [[Convolutional neural network]].
| {{no}}
| {{n/a}}
|-
| [[Double-checked locking]]
| Reduce the overhead of acquiring a lock by first testing the locking criterion (the 'lock hint') in an unsafe manner; only if that succeeds does the actual locking logic proceed.
Can be unsafe when implemented in some language/hardware combinations. It can therefore sometimes be considered an [[anti-pattern]].
| {{yes}}
| {{n/a}}
|-
| [[Event-Based Asynchronous Pattern|Event-based asynchronous]]
| Addresses problems with the asynchronous pattern that occur in multithreaded programs.<ref name="PC#2008">{{cite book|title = Professional C# 2008| first1 = Christian | last1 = Nagel | first2 = Bill | last2 = Evjen | first3 = Jay | last3 = Glynn | first4 = Karli | last4 = Watson | first5 = Morgan | last5 = Skinner|pages = 570–571|publisher = Wiley|year = 2008|isbn = 978-0-470-19137-8|chapter = Event-based Asynchronous Pattern}}</ref>
| {{no}}
| {{n/a}}
|-
| [[Guarded suspension]]
| Manages operations that require both a lock to be acquired and a precondition to be satisfied before the operation can be executed.
| {{no}}
| {{n/a}}
|-
| [[Join-pattern|Join]]
| Join-pattern provides a way to write concurrent, parallel and distributed programs by message passing. Compared to the use of threads and locks, this is a high-level programming model.
| {{no}}
| {{n/a}}
|-
| [[Lock (computer science)|Lock]]
| One thread puts a "lock" on a resource, preventing other threads from accessing or modifying it.<ref>[http://c2.com/cgi/wiki?LockPattern Lock Pattern<!-- Bot generated title -->]</ref>
| {{no}}
| {{yes|PoEAA<ref name = "PoEAA"/>}}
|-
| [[Messaging pattern|Messaging design pattern (MDP)]]
| Allows the interchange of information (i.e. messages) between components and applications.
| {{no}}
| {{n/a}}
|-
| [[Monitor (synchronization)|Monitor object]]
| An object whose methods are subject to [[mutual exclusion]], thus preventing multiple objects from erroneously trying to use it at the same time.
| {{yes}}
| {{n/a}}
|-
| [[Reactor pattern|Reactor]]
| A reactor object provides an asynchronous interface to resources that must be handled synchronously.
| {{yes}}
| {{n/a}}
|-
| [[Read-write lock]]
| Allows concurrent read access to an object, but requires exclusive access for write operations. An underlying semaphore might be used for writing, and a [[Copy-on-write]] mechanism may or may not be used.
| {{no}}
| {{n/a}}
|-
| [[Scheduler pattern|Scheduler]]
| Explicitly control when threads may execute single-threaded code.
| {{no}}
| {{n/a}}
|-
| Service handler pattern
| For each request, a server spawns a dedicated client handler to handle a request.<ref>{{cite journal |last1=Francalanza |first1=Adrian |last2=Tabone |first2=Gerard |title=ElixirST: A session-based type system for Elixir modules |journal=Journal of Logical and Algebraic Methods in Programming |date=October 2023 |volume=135 |doi=10.1016/j.jlamp.2023.100891|s2cid=251442539 }}</ref> Also referred to as ''thread-per-session''.<ref>{{cite journal |last1=Schmidt |first1=Douglas C. |last2=Vinoski |first2=Steve |title=Object Interconnections: Comparing Alternative Programming Techniques for Multi-threaded CORBA Servers (Column 7) |date=July–August 1996 |journal=SIGS C++ Report |url=https://www.dre.vanderbilt.edu/~schmidt/PDF/C++-report-col7.pdf |s2cid=2654843}}</ref>
| {{no}}
| {{n/a}}
|-
| [[Thread pool]]
| A number of threads are created to perform a number of tasks, which are usually organized in a queue. Typically, there are many more tasks than threads. Can be considered a special case of the [[object pool]] pattern.
| {{no}}
| {{n/a}}
|-
| [[Thread-specific storage]]
| Static or "global" memory local to a thread.
| {{yes}}
| {{n/a}}
|-
| Safe Concurrency with Exclusive Ownership
| Avoiding the need for runtime concurrent mechanisms, because exclusive ownership can be proven. This is a notable capability of the Rust language, but compile-time checking isn't the only means, a programmer will often manually design such patterns into code - omitting the use of locking mechanism because the programmer assesses that a given variable is never going to be concurrently accessed.
| {{no}}
| {{n/a}}
|-
| CPU atomic operation
| x86 and other CPU architectures support a range of atomic instructions that guarantee memory safety for modifying and accessing primitive values (integers). For example, two threads may both increment a counter safely. These capabilities can also be used to implement the mechanisms for other concurrency patterns as above. The [[C Sharp (programming language)|C#]] language uses the [https://docs.microsoft.com/en-us/dotnet/api/system.threading.interlocked?view=net-5.0 Interlocked] class for these capabilities.
| {{no}}
| {{n/a}}
|}