Does pthreads provide any advantages over GCD?

user_139685 0
Viewed 7453

Having recently learned Grand Central Dispatch, I've found multithreaded code to be pretty intuitive(with GCD). I like the fact that no locks are required(and the fact that it uses lockless data structures internally), and that the API is very simple.

Now, I'm beginning to learn pthreads, and I can't help but be a little overwhelmed with the complexity. Thread joins, mutexes, condition variables- all of these things aren't necessary in GCD, but have a lot of API calls in pthreads.

Does pthreads provide any advantages over GCD? Is it more efficient? Are there normal-use cases where pthreads can do things that GCD can not do(excluding kernel-level software)?

In terms of cross-platform compatibility, I'm not too concerned. After all, libdispatch is open source, Apple has submtited their closure changes as patches to GCC, clang supports closures, and already(e.x. FreeBSD), we're starting to see some non-Apple implementations of GCD. I'm mostly interested in use of the API(specific examples would be great!).

grand-central-dispatch pthreads multithreading
6 Answers

That overwhelming feeling that you are experiencing.. that's exactly why GCD was invented.

At the most basic level there are threads, pthreads is a POSIX API for threads so you can write code in any compliant OS and expect it to work. GCD is built on top of threads (although I'm not sure if they actually used pthreads as the API). I believe GCD only works on OS X and iOS — that in a nutshell is its main disadvantage.

Note that projects that make heavy use of threads and require high performance implement their own version of thread pools. GCD allows you to avoid (re)inventing the wheel for the umpteenth time.

user_1677350

GCD is an Apple technology, and not the most cross platform compatible; pthread are available on just about everything from OSX, Linux, Unix, Windows.. including this toaster

GCD is optimized for thread pool parallelism. Pthreads are (as you said) very complex building blocks for parallelism, you are left to develop your own models. I highly recommend picking up a book on the topic if you're interested in learning more about pthreads and different models of parallelism.

user_2139910

As any declarative/assisted approach like openmp or Intel TBB GCD should be very good at embarrassingly parallel problems and will probably easily beat naïve manually pthread-ed parallel sort. I would suggest you still learn pthreads though. You'll understand concurrency better, you'd be able to apply right tool in each particular situation, and if for nothing else - there's ton of pthread-based code out there - you'd be able to read "legacy" code.

user_1066710
Related