On Wed, Jul 1, 2009 at 4:16 PM, Francesco Petrogalli<[email protected]> wrote: > Hi, sorry for the long wait for my answer, but I've been very busy. > > I'll try to be more exhaustive about my problem. My question is very > simple: why is sbcl slower on a four core cpu (Intel Core duo quad) > than on an old machine like my Intel pentium (single core). > > I mean, my program runs on a single thread, but shouldn't be the > single thread of the quad core cpu faster than the single thread of > the single core cpu, being the latter at a lower frequency of the quad > core? > > The fact is that the difference in speed is not of few seconds, but of > 10 seconds versus the 2 minutes of the quad core.... > > The program is very simple, it uses only a small amount of memory. It > takes an image in PGM format (200x200 pixels) and finds the edges of > the objects in the image using an algorithm based on fuzzy logic. The > percentage of CPU used on the single core CPU is 100% (for 10 seconds) > and 25% on the quad core (this is as I expected... a single thread on > a quad core cpu takes 1/4 of the CPU...)
Sorry, maybe I've already asked this to you and then forgotten about it, but: are both your processors 64-bit? Couldn't it be the case that on the newer one you're using sbcl compiled for 32-bit i386, and that runs in emulated 32-bit mode on a 64-bit processor, while on the older machine it runs natively as 32-bit? Given that you're manipulating arrays, and probably iterating over them many times, the difference between emulated and native 32-bit might be important. I'm just speculating because I'm pretty much ignorant about processor architectures. > Well, that's all, I hope I've been more clear this time. (sorry for my > bad english) > > Below you find some news about my sbcl version. > > Bye > > franZ > >>> CL-USER(7): (LISP-IMPLEMENTATION-VERSION) >>> >>> "1.0.29.11.debian" > > I use Lenny, my version is "1.0.18.debian" > >>> CL-USER(8): (not (not (member :SB-THREAD *features*))) >>> >>> T > > same result, like yours What does uname -a return on each machine? Bye, Alessio _______________________________________________ Gardeners mailing list [email protected] http://www.lispniks.com/mailman/listinfo/gardeners
