c# - Making the most of the .NET Task Parallel Library

Question

Question 1.

Is using Parallel.For and Parallel.ForEach better suited to working with tasks that are ordered or unordered?

My reason for asking is that I recently updated a serial loop where a StringBuilder was being used to generate a SQL statement based on various parameters. The result was that the SQL was a bit jumbled up (to the point it contained syntax errors) in comparison to when using a standard foreach loop, therefore my gut feeling is that TPL is not suited to performing tasks where the data must appear in a particular order.

Question 2.

Does the TPL automatically make use of multicore architectures of must I provision anything prior to execution?

My reason for asking this relates back to an eariler question I asked relating to performance profiling of TPL operations. An answer to the question enlightened me to the fact that TPL is not always more efficient than a standard serial loop as the application may not have access to multiple cores, and therefore the overhead of creating additional threads and loops would create a performance decrease in comparison to a standard serial loop.

Answer 1

my gut feeling is that TPL is not suited to performing tasks where the data must appear in a particular order.

Correct. If you expect things in order, you might have a misunderstanding about what's going to happen when you "parallelize" a loop.

Does the TPL automatically make use of multicore architectures of must I provision anything prior to execution?

See the following article on the msdn magazine: http://msdn.microsoft.com/en-us/magazine/cc163340.aspx

Using the library, you can conveniently express potential parallelism in existing sequential code, where the exposed parallel tasks will be run concurrently on all available processors.