Determine if the following problems exhibit task or data parallelism

Question

Determine if the following problems exhibit task or data parallelism:

1. Using a separate thread to generate a thumbnail for each photo in a collection

2. Transposing a matrix in parallel

3. A networked application where one thread reads from the network and another writes to the network

4. The Grand Central Dispatch system

Answer 1

Typically for data parallelism you will be sharing the same dataset and performing multiple iterations of the same algorithm across cores/processors. Task parallelism is used for performing distinct processes across multiple cores/processors. There is some overlap but they are logically distinct. It is possible to have an application that does both. Frequently in that case the larger-scale functions will use task parallelism and will execute lower-level functions that perform data parallelism.

Key phrases to look for in this sort of a problem:

"for each ... in a collection" = task parallelism

"transposing ... in parallel" = data parallelism

"from one .. to another" = task parallelism

Any complex system could use both.