Multi core programming

Question

I want to get into multi core programming (not language specific) and wondered what hardware could be recommended for exploring this field. My aim is to upgrade my existing desktop.

Answer 1

I'd recommend at least a quad-core processor.

Answer 2

You could try tinkering with CUDA. It's free, not that hard to use and will run on any recent NVIDIA card.

Alternatively, you could get a PlayStation 3 and the Linux SDK and work out how to program a Cell processor. Note that the next cheapest option for Cell BE development is an order of magnitude more expensive than a PS3.

Finally, any modern motherboard that will take a Core Quad or quad-core Opteron (get a good one from Asus or some other reputable manufacturer) will let you experiment with a multi-core PC system for a reasonable sum of money.

Answer 3

I agree with the others where I would upgrade to a quad-core processor. I am also a BIG FAN of ASUS Motherboards (the P5Q Pro is excellent for Core2Quad and Core2Duo processors)!

The draw for multi-core programming is that you have more resources to get things done faster. If you are serious about multi-core programming, then I would absolutely get a quad-core processor. I don't believe that you should get the new i7 architecture from Intel to take advantage of multi-core processing because anything written to take advantage of the Core2Duo or Core2Quad will just run better on the newer architecture.

If you are going to dabble in multi-core programming, then I would get a good Core2Duo processor. Remember, it's not just how many cores you have, but also how FAST the cores are to process the jobs. My Core2Duo running at 4GHz routinely completes jobs faster than my Core2Quad running at 2.4GHz even with a multi-core program.

Let me know if this helps! JFV

Answer 4

Quad-core, because it'll permit you to do problems where the number of concurrent processes is > 2, which often non-trivializes problems.

I would also, for sheer geek squee, pick up a nice NVidia card and use the CUDA API. If you have the bucks, there's a stand-alone CUDA workstation that plugs into your main computer via a cable and an expansion slot.

Answer 5

The difficult thing with multithreaded/core programming is that it opens a whole new can of worms. The bugs you'll be faced with are usually not the one you're used to. Race conditions can remain dormant for ages until they bite and your mainstream language compiler won't assist you in any way. You'll get random data and/or crashes that only happen once a day/week/month/year, usually under the most mysterious conditions...

One things remains true fortunately : the higher the concurrency exhibited by a computer, the more race conditions you'll unveil.

So if you're serious about multithreaded/core programming, then go for as many cpu cores as possible. Keep in mind that neither hyperthreading nor SMT allow for the level of concurrency that multiple cores provide.

Answer 6

If at all possible, I would suggest getting a dual-socket machine, preferably with quad-core chips. You can certainly get a single-socket machine, but dual-socket would let you start seeing some of the effects of NUMA memory that are going to be exacerbated as the core counts get higher and higher.

Why do you care? There are two huge problems facing multi-core developers right now:

1. The programming model Parallel programming is hard, and there is (currently) no getting around this. A quad-core system will let you start playing around with real concurrency and all of the popular paradigms (threads, UPC, MPI, OpenMP, etc).

2. Memory Whenever you start having multiple threads, there is going to be contention for resources, and the memory wall is growing larger and larger. A recent article at arstechnica outlines some (very preliminary) research at Sandia that shows just how bad this might become if current trends continue. Multicore machines are going to have to keep everything fed, and this will require that people be intimately familiar with their memory system. Dual-socket adds NUMA to the mix (at least on AMD machines), which should get you started down this difficult road.

If you're interested in more info on performance inconsistencies with multi-socket machines, you might also check out this technical report on the subject.

Also, others have suggested getting a system with a CUDA-capable GPU, which I think is also a great way to get into multithreaded programming. It's lower level than the stuff I mentioned above, but throw one of those on your machine if you can. The new Portland Group compilers have provisional support for optimizing loops with CUDA, so you could play around with your GPU even if you don't want to learn CUDA yourself.

Answer 7

It depends what you want to do.

If you want to learn the basics of multithreaded programming, then you can do that on your existing single-core PC. (If you have 2 threads, then the OS will switch between them on a single-core PC. Then when you move to a dual-core PC they should automatically run in parallel on separate cores, for a 2x speedup). This has the advantage of being free! The disadvantages are that you won't see a speedup (in fact a parallel implementation is probably slightly slower due to overheads), and that buggy code has a slightly higher chance of working.

However, although you can learn multithreaded programming on a single-core box, a dual-core (or even HyperThreading) CPU would be a great help.

If you want to really stress-test the code you're writing, then as "blue tuxedo" says, you should go for as many cores as you can easily afford, and if possible get hyperthreading too.

If you want to learn about algorithms for running on graphics cards - which is a very different area to x86 multicore - then get CUDA and buy a normal nVidia graphics card that supports it.

Answer 8

I would agree that, depending on what you ultimately want to do, you can probably get by with just your current single-core system. Multi-core programming is basically multi-threaded programming, and you can certainly do that on a single-core chip.

When I was a student, one of our projects was to build a thread-safe implementation the malloc library for C. Even on a single core processor, that was more than enough to cure me of my desire to get into multi-threaded programming. I would try something small like that before you start thinking about spending lots of money.