.NET Parallel Programming

All about Async/Await, System.Threading.Tasks, System.Collections.Concurrent, System.Linq, and more…

Concurrency Visualizer: A Case Study

Boby George and Pooja Nagpal - testers on the Parallel Computing Platform team responsible for the parallel programming support in .NET 4- built a parallel spell checker algorithm and used the Concurrency Visualizer to analyze and improve the performance and scalability of their implementation.Optimizing Parallel Applications Using ...

PLINQ’s Ordering Model

In order to execute parallel queries as efficiently as possible, Parallel LINQ (PLINQ) treats ordering as optional. By default, PLINQ considers sequences to be unordered, unless the user explicitly opts into maintaining ordering using either the AsOrdered or the OrderBy operator.Roy Patrick Tan wrote a detailed article that...

Why is TaskContinuationsOptions.ExecuteSynchronously opt-in?

For a relatively advanced feature, I've been surprised how often this question has come up recently. When a task completes, its continuations become available for execution, and by default, a continuation will be scheduled for execution rather than executed immediately.  This means that the continuation has to be queued to the ...

ParallelExtensionsExtras Tour – #16 – Async Tasks for WebClient, SmtpClient, and Ping

(The full set of ParallelExtensionsExtras Tour posts is available here.) The Task Parallel Library isn’t just about CPU-bound operations.  The Task class is a great representation for any asynchronous operation, even those implemented purely as asynchronous I/O.Task’s ability to represent arbitrary asynchronous operations ...

ParallelExtensionsExtras Tour – #15 – Specialized Task Waiting

(The full set of ParallelExtensionsExtras Tour posts is available here.)The Task Parallel Library provides the Task.Wait method, which synchronously waits for the target Task to complete.  If the Task completed successfully, the method simply returns.  If the Task completed due to an unhandled exception or cancellation, Wait throws ...

A TPL Sandbox

In a previous post, we introduced the UnobservedTaskException event, saying that it would be useful for host-plugin scenarios where a host application should continue to execute in the presence of exceptions thrown by buggy plugins.  A typical example is an Internet browser; should the entire application crash if some rich content plugin ...

ParallelExtensionsExtras Tour – #14 – SingleItemPartitioner

(The full set of ParallelExtensionsExtras Tour posts is available here.) In a previous ParallelExtensionsExtras Tour blog post, we talked about implementing a custom partitioner for BlockingCollection<T>.  Custom partitioning is an advanced but important feature supported by both Parallel.ForEach and PLINQ, as it allows the ...

ParallelExtensionsExtras Tour – #13 – AsyncCall

(The full set of ParallelExtensionsExtras Tour posts is available here.)Producer/consumer scenarios could logically be split into two categories: those where the consumers are synchronous, blocking waiting for producers to generate data, and those where the consumers are asynchronous, such that they're alerted to data being available and only ...

Performance of Concurrent Collections in .NET 4

.NET 4 introduces new data structures designed to simplify thread-safe access to shared data, and to increase the performance and scalability of multi-threaded applications. To best take advantage of these data structures, it helps to understand their performance characteristics in different scenarios.Chunyan Song, Emad Omara and Mike Liddell ...

ParallelExtensionsExtras Tour – #12 – AsyncCache

(The full set of ParallelExtensionsExtras Tour posts is available here.)Caches are ubiquitous in computing, serving as a staple of both hardware architecture and software development.  In software, caches are often implemented as dictionaries, where some data is retrieved or computed based on a key, and then that key and its resulting ...

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