The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Thursday, November 29, 2007

More stupid multithreaded benchmarks

The other interesting thing to think about: at what point do we beat the same algorithm in C, and how hard would it be to parallelise the algorithm in C with pthreads

Use those extra cores and beat C today! (Parallel Haskell redux)

Since I'm doing stupid benchmarks anyway, why not this? I didn't use pthreads though—I haven't used that particular API in about a decade, and even then, I wasn't thrilled with it.

Nope. Instead I used a Linux specific call—clone(), wrote a small function to wait for all the threads that were created, and basically spent about five minutes making a parallelized C-version of the Fibonacci sequence. Granted, I had to do the parallelization explicitly, but it wasn't that difficult to do.

The hard part was finding a quad-core box to test this on. Fortunately, I know we have one at The Company (shhh—don't tell Smirk) and that's where I spent most of my time on this—locating our single quad-core machine I could test this on.

But find it I did. And yes, the program does run faster the more cores that are thrown at it, but it's not a linear speed up:

A Parallelized Fibonacci Sequence calculation program
# cores Runtime
1 0m31.468s
2 0m19.521s
4 0m17.234s

It's interesting that it appears to be bottoming out rather quickly (and these are average times over a few runs).

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