Task parallelism¶

Category: Parallelism · Status: stub · Lessons: chapter 07, Parallelism

One line: Different tasks, possibly doing different things, running at the same time on different cores.

How it connects¶

flowchart LR
  n_data_parallelism["Data parallelism"]
  n_fork_join["Fork-join"]
  n_parallelism["Parallelism"]
  n_task_parallelism["Task parallelism"]
  n_data_parallelism ---|vs| n_task_parallelism
  n_fork_join -->|is a| n_task_parallelism
  n_task_parallelism -->|is a| n_parallelism
  classDef center stroke-width:3px
  class n_task_parallelism center
  classDef outside stroke-dasharray: 4 3
  class n_data_parallelism,n_fork_join,n_parallelism outside

Is a kind of: Parallelism
Kinds: Fork-join
Often confused with: Data parallelism

In each language¶


Rust	Rayon's `join` ↗ runs two closures, potentially in parallel
Go	`go` statements, with a `sync.WaitGroup` ↗ to wait for them
C++	`std::async` ↗ with `std::launch::async`
Java	`ForkJoinTask` ↗ `fork` and `join`; `StructuredTaskScope` ↗ is still a preview API in JDK 25
Python	`Executor.submit` ↗
C#	`Parallel.Invoke` ↗ and task parallelism ↗
Swift	`async let` and task groups ↗

Where to read more¶

In the books: Concurrent Programming on Windows, Joe Duffy — ch. 13, 'Data and Task Parallelism'
In the books: Pro Asynchronous Programming with .NET, Richard Blewett, Andrew Clymer — ch. 10, 'TPL Dataflow'
In the books: Pro TBB, Michael Voss, Rafael Asenjo, James Reinders — ch. 2, 'Generic Parallel Algorithms' → 'Functional / Task Parallelism'
In the books: Programming Concurrency on the JVM, Venkat Subramaniam — ch. 4, 'Scalability and Thread Safety' → 'Java 7 Fork-Join API'
In the books: Parallel Programming and Concurrency with C# 10 and .NET 6, Alvin Ashcraft — ch. 6, 'Parallel Programming Concepts' → 'Getting started with the TPL'
In the books: Concurrency in .NET, Riccardo Terrell — ch. 7, 'Task-based functional parallelism' → 'The .NET Task Parallel Library'
Reference: Wikipedia: Task parallelism ↗