C++ Parallelization Libraries: OpenMP vs. Thread Building Blocks [closed]

Question

I'm going to retrofit my custom graphics engine so that it takes advantage of multicore CPUs. More exactly, I am looking for a library to parallelize loops.

It seems to me that both OpenMP and Intel's Thread Building Blocks are very well suited for the job. Also, both are supported by Visual Studio's C++ compiler and most other popular compilers. And both libraries seem quite straight-forward to use.

So, which one should I choose? Has anyone tried both libraries and can give me some cons and pros of using either library? Also, what did you choose to work with in the end?

Thanks,

Adrian

Answer 1

I haven't used TBB extensively, but my impression is that they complement each other more than competing. TBB provides threadsafe containers and some parallel algorithms, whereas OpenMP is more of a way to parallelise existing code.

Personally I've found OpenMP very easy to drop into existing code where you have a parallelisable loop or bunch of sections that can be run in parallel. However it doesn't help you particularly for a case where you need to modify some shared data - where TBB's concurrent containers might be exactly what you want.

If all you want is to parallelise loops where the iterations are independent (or can be fairly easily made so), I'd go for OpenMP. If you're going to need more interaction between the threads, I think TBB may offer a little more in that regard.

Answer 2

From Intel's software blog: Compare Windows* threads, OpenMP*, Intel® Threading Building Blocks for parallel programming

It is also the matter of style - for me TBB is very C++ like, while I don't like OpenMP pragmas that much (reeks of C a bit, would use it if I had to write in C).

I would also consider the existing knowledge and experience of the team. Learning a new library (especially when it comes to threading/concurrency) does take some time. I think that for now, OpenMP is more widely known and deployed than TBB (but this is just mine opinion).

Yet another factor - but considering most common platforms, probably not an issue - portability. But the license might be an issue.

• TBB incorporates some of nice research originating from academic research, for example recursive data parallel approach.
• There is some work on cache-friendliness, for example.
• Lecture of the Intel blog seems really interesting.